U.S. patent application number 12/716846 was filed with the patent office on 2010-09-02 for method and apparatus for using light emitting diodes.
Invention is credited to Jonathan S. Dahm.
Application Number | 20100220472 12/716846 |
Document ID | / |
Family ID | 31192578 |
Filed Date | 2010-09-02 |
United States Patent
Application |
20100220472 |
Kind Code |
A1 |
Dahm; Jonathan S. |
September 2, 2010 |
METHOD AND APPARATUS FOR USING LIGHT EMITTING DIODES
Abstract
The present invention provides a method and apparatus for using
light emitting diodes for curing in various applications. The
method includes a novel method for cooling the light emitting
diodes and mounting the same on heat pipe in a manner which
delivers ultra high power in UV, visible and IR regions.
Furthermore, the unique LED packaging technology of the present
invention that utilizes heat pipes performs far more efficiently in
much more compact space. This allows much more closely spaced LEDs
operating at higher power and brightness.
Inventors: |
Dahm; Jonathan S.;
(Longmont, CO) |
Correspondence
Address: |
LANDO & ANASTASI, LLP
ONE MAIN STREET, SUITE 1100
CAMBRIDGE
MA
02142
US
|
Family ID: |
31192578 |
Appl. No.: |
12/716846 |
Filed: |
March 3, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11042970 |
Jan 24, 2005 |
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12716846 |
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PCT/US2003/023504 |
Jul 25, 2003 |
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11042970 |
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60398635 |
Jul 25, 2002 |
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60405432 |
Aug 23, 2002 |
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60410720 |
Sep 13, 2002 |
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60416948 |
Oct 8, 2002 |
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60420479 |
Oct 21, 2002 |
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60467702 |
May 3, 2003 |
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60476004 |
Jun 4, 2003 |
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Current U.S.
Class: |
362/231 ;
362/235; 362/294; 362/373 |
Current CPC
Class: |
A61C 19/004 20130101;
H01L 2924/12044 20130101; F28D 15/02 20130101; H01L 2224/73265
20130101; A61N 2005/0652 20130101; F21V 29/51 20150115; H05K 1/0203
20130101; H05K 2201/10106 20130101; H01L 2924/00 20130101; H01L
2924/12044 20130101; H01L 2924/00014 20130101; H01L 2224/48091
20130101; H05K 1/0209 20130101; H01L 2224/48091 20130101; F21Y
2115/10 20160801 |
Class at
Publication: |
362/231 ;
362/373; 362/294; 362/235 |
International
Class: |
F21V 9/00 20060101
F21V009/00; F21V 29/00 20060101 F21V029/00 |
Claims
1. (canceled)
2. A device for providing light in a predetermined direction, the
device comprising: a heat pipe having a first and second end; a
light emitting device mounted adjacent to the first end of the heat
pipe and electrically connected to the heat pipe; and a sleeve
around the light emitting device and the heat pipe; wherein said
sleeve is electrically insulated from said heat pipe and said light
emitting device is electrically coupled to said sleeve.
3-4. (canceled)
5. A light emitting apparatus comprising: a heat pipe having an
evaporating a condensing end; a light emitting device mounted on
the evaporating end of the heat pipe; and a color mixing totally
internally reflecting concentrator in optical communication with
the light emitting device.
6. The device of claim 5, further comprising: at least two light
emitting devices emitting at substantially different
wavelengths.
7. The device of claim 5, further comprising: individually
addressable light emitting devices.
8. The device of claim 5, further comprising: pulse width
modulation of the light emitting devices.
9. A light emitting device, the device comprising: a substrate
having at least one heat pipe; at least two light emitting devices
mounted on the substrate; and a wavelength mixing substrate, each
light emitting device a different wavelength; wherein each light
emitting device is in optical communication with said wavelength
mixing substrate.
10. The device of claim 9 wherein the wavelength mixing substrate
is refractive micro lens array.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS:
[0001] This application is a continuation of International
Application No. PCT/US2003/023504 filed on Jul. 25, 2003, and which
designated the U.S., which claims benefit of priority of U.S.
Provisional Application Nos. 60/398,635, filed Jul. 25, 2002;
60/405,432, filed Aug. 23, 2002; 60/410,720, filed Sep. 13, 2002;
60/416,948, filed Oct. 8, 2002; 60/420,479, filed Oct. 21, 2002;
60/467,702, filed May 3, 2003 and 60/476,004, filed on Jun. 4,
2003.
FIELD OF THE INVENTION
[0002] This invention relates to the field of light emitting diode
("LED") technology, particularly to improvement in the output of
light therefrom for curing curable compositions and forming cured
parts from curable composition after exposure thereto.
BACKGROUND OF THE INVENTION
[0003] Heat can damage sensitive electronic components, degrading
reliability and hampering the ability to concentrate higher power
levels into smaller packages. Many applications would benefit from
the ability to closely package LEDs into compact configurations,
but the heat levels generated have always been a limiting factor.
As LEDs become more sophisticated, eliminating internal heat
build-up has also become increasingly difficult. Devices are
becoming more powerful and creating solutions for removing the
resulting heat generation often pose great challenges.
[0004] U.S. Patent Publication No. 2003/0036031 to Lieb et al.
discloses a light-emitting handpiece for curing light-curable
dental resins and similar materials. The device includes a head
portion for supporting a LED light source, a tubular handle portion
for containing a power source for energizing the LED light source
and a neck portion that interconnects the head and handle portions.
The head and the neck portions are integrally formed from a common,
thermally conductive material and operate to provide a heat sink
for the LED. A substantial portion of the light source housing
itself functions to dissipate sufficient thermal energy away from
the LED allowing the LED to be operated for a time interval
sufficient to effect resin curing.
[0005] In U.S. Patent Publication No. 2003/0021310 to Harding,
there is disclosed a method and apparatus for cooling electronic or
opto-electronic devices. The apparatus includes the device mounted
on a heat sink assembly within a can having a can body and a can
header thermally coupled to the heat sink assembly and closing the
can body and a thermal conductor outside the can and having a first
portion attached to at least part of an edge of the can header and
a second portion attached to a thermal sink outside the can.
[0006] In U.S. Pat. No. 6,159,005 to Herold et al., there is
disclosed a small, light-weight handy device for photo polymerizing
synthetic materials. The device includes a built-in battery, a
light source constituted by an LED which emits a small useful
spectrally range only, thereby avoiding any heat radiation. The LED
is preferably located at the tip of the device directing towards
the site to be polymerized.
[0007] In U.S. Pat. No. 6,523,959 to Lu et al., there is disclosed
a cooling device utilized to cool a liquid crystal panel and
polarizer of an optical system in a liquid crystal projector. The
cooling device includes a heat dissipation system comprising a
plurality of heat pipes disposed at the two flank sides of said
liquid crystal panel.
[0008] None of these U.S. patent documents disclose LED cooling in
a manner to dissipate internal heat energy and packaging the same
to achieve maximum light output. Thus, a need exists for cooling
the LEDs and mounting the same on the heat pipes in a manner which
greatly surpasses the performance of conventional cooling
techniques and benefit high-density, miniatured LED components.
Furthermore, there is a need for a novel LED packaging technology
that channels heat away via state-of-the-art micro heat pipes that
perform far more efficiently, and in much more compact space, than
conventional heat sink technology.
SUMMARY OF THE INVENTION
[0009] In a first embodiment of the present invention there is
provided a method and device for curing adhesives on a surface. The
method includes providing at least one LED, passing a coolant into
the LED through at least one channel to effect cooling of the LED
and irradiating the adhesive on the surface with the LED to cure
the adhesive. The device includes a power supply, a radiation
source having a radiation output and including at least one LED
coupled to the power supply and at least one channel coupled to the
LED, wherein a coolant is passed into the LED via the channel
thereby cooling the LEDs to deliver a high light output on the
adhesives.
[0010] In a second embodiment of the present invention there is
provided a method for cooling LEDs. The method includes providing
at least one LED, connecting at least one channel to the LED to
create a path and injecting a coolant through the channel to cool
the LEDs.
[0011] In a third embodiment of the present invention, there is
provided an LED curing device. The device includes a tubular body
having two opposing ends, an LED body including a highly conductive
surface placed at one opposing end and a heat pipe connected to the
conductive surface of the LED body. The heat pipe serves to
transport heat away from the LED body.
[0012] In a fourth embodiment of the present invention, there is
provided a device for transporting thermal energy. The device
includes a copper heat sink, an array of LEDs and at least one heat
pipe of tubular shape. The copper heat sink has at least one vapor
cavity. The array of LEDs are attached to the heat sink wherein a
long axis of the vapor cavity is substantially perpendicular to the
p-n junctions of the LEDs. The heat pipe of tubular shape is
inserted into the heat sink via the vapor cavity, wherein thermal
energy is transported away from the array of LEDs in a
substantially opposite direction from light emitting from the
LED.
[0013] In a fifth embodiment of the present invention, there is
provided an LED device package. The LED device package includes a
conductive substrate, a heat pipe connected to the conductive
substrate and at least one LED mounted onto a tip of the heat pipe,
wherein heat is transported away from the LED.
[0014] In a sixth embodiment of the present invention, there is
provided an LED curing device. The LED curing device includes a
tubular body, an LED body, a heat pipe, a power source, a fan and a
heat sink/exchanger. The tubular body has two opposed ends
including a wide end and a tip end. The LED body includes a
conductive surface and is placed at the tip end of the tubular
body. The heat pipe extends through the tubular body and is bonded
to the conductive surface of the LED body. The power source is
located around the middle portion of the tubular body for powering
the LED. The fan is situated at the wide end of the body. Finally,
the heat sink/exchanger is placed between the power source and the
fan to receive air blown out from the fan.
[0015] In a seventh embodiment of the present invention, there is
provided an apparatus for transporting heat and/or thermal energy.
The apparatus comprises at least one heat pipe and an LED device.
Each heat pipe has a first end and a second end. The first end
serves as an evaporating end and the second end is the condensing
end. The LED is mounted at the first end of each heat pipe, wherein
heat and/or thermal energy is transported in a general direction
away from each LED, i.e. away from the first end toward the second
end of the respective heat pipe.
[0016] In an eighth embodiment of the present invention, there is
provided an apparatus for transporting heat. The apparatus includes
a heat transporting device, an LED and a transport means. The heat
transporting device has a first end and a second end. The LED is
mounted at the first end of the heat transporting device. The
transport means is associated with the heat transporting device for
transporting heat generate by the LED from the first end to the
second end.
[0017] In a ninth embodiment of the present invention, there is
provided a device for providing light in a predetermined direction.
The device includes a heat pipe, an LED, a power supply, an
activation switch and a housing. The heat pipe has a first end and
a second end. The LED is mounted at the first end of the heat pipe.
The power supply powers the LED. The activation switch activates
the power supply. The housing surrounds at least a portion of the
heat pipe.
[0018] In a tenth embodiment of the present invention, there is
provided a light emitting apparatus. The apparatus includes an
electrically conductive heat pipe and an LED mounted on a tip of
the heat pipe, wherein the heat pipe provides electricity for the
LED and transports heat from the LED.
[0019] In an eleventh embodiment of the present invention, there is
provided an apparatus for transporting thermal energy. The
apparatus includes an array of heat pipes and an LED. Each heat
pipe in the array of heat pipes has a first end, a second end and a
cavity extending from the first end to the second end. The LED is
mounted to the first end of each heat pipe. Each LED has a p-n
junction, wherein at least a portion of the cavity is substantially
perpendicular to the p-n junction of the LED.
[0020] In a twelfth embodiment of the present invention, there is
provided an LED device. The LED device includes a substrate and at
least one LED. The substrate has at least one heat pipe. The LED is
mounted on the substrate, wherein heat generated by the LED travels
in a substantially opposite direction from light emitted from the
LED.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 illustrates a conventional LED device.
[0022] FIG. 2 illustrates a perspective view of a device having an
array of LEDs.
[0023] FIG. 3 shows a perspective view of a device having an array
of LEDs in a mold cavity.
[0024] FIG. 4 shows a device of the present invention having an
array of LEDs with the electrical connection.
[0025] FIG. 5 illustrates a forced convecting cooling to a device
having an array of LEDs.
[0026] FIG. 6a shows a perspective view of a hand held LED curing
device according to the present invention.
[0027] FIG. 6b is an expanded view of the tip end of the device in
FIG. 6a.
[0028] FIG. 7 illustrates a perspective view of a liquid-cooled
version of the LED hand held curing device according to the present
invention.
[0029] FIG. 7a is an expanded view of the front end of the device
in FIG. 7.
[0030] FIG. 7b is an expanded view of the tip end of the device in
FIG. 7.
[0031] FIG. 8 shows an LED curing device in which heat pipe
provides both coolant and electrical connection according to an
alternate embodiment of the present invention.
[0032] FIG. 8a shows an expanded view of the tip of the device of
FIG. 8 with multiple LEDs.
[0033] FIG. 9 is a perspective view of an alternate light-emitting
device that is cooled by a phase change material.
[0034] FIG. 9a shows an adhesive curing device in accordance with
an embodiment of the present invention.
[0035] FIGS. 9b and 9c illustrate a device including multiple LED
array with detachable fins according to an alternate embodiment of
the present invention.
[0036] FIG. 10 shows a device having an array of large area UV or
visible LEDs mounted on multiple sinks and cooled by an array of
heat pipes according to an alternate embodiment of the present
invention.
[0037] FIGS. 11, 11a, 11b, 11c, 11d, 11e and 11f illustrate various
embodiments of a novel packaging of LEDs and heat pipes according
to the present invention.
[0038] FIGS. 12, 12a, 12b, 12c, 12d and 12e illustrate various
embodiments of the LED/heat pipe assembly according to the present
invention.
[0039] FIG. 13 shows a perspective view of the LED/heat pipe device
on a circuit board.
[0040] FIG. 14 shows an array formed of more than one device of
FIG. 13.
[0041] FIG. 14a is a cross-sectional view of the arrayed devices of
FIG. 14.
[0042] FIGS. 14b, 14c and 14d illustrate devices having multiple
heat pipes with different spacing and geometric patterns including
multiple LEDs.
[0043] FIG. 14e shows the devices of FIGS. 14b, 14c and 14d placed
in the circuit board.
[0044] FIGS. 14f and 14g show a device having a single heat pipe
including multiple LEDs connected to a circuit board.
[0045] FIGS. 15a and 15b illustrate a perspective view of multiple
LEDs on heat pipes arrayed on a circuit board.
[0046] FIG. 15c is a side view of two heat pipes of FIG. 15b in the
circuit board.
[0047] FIG. 15d illustrates a forced-air cooled hand held device
according to an embodiment of the present invention.
[0048] FIG. 15e shows a perspective view of multiple LEDs disposed
on the end of the heat pipe.
[0049] FIG. 16 shows a device where vertical cavity surface
emitting laser (VCSEL) is bonded to the heat pipe in an alternate
embodiment of the present invention.
[0050] FIGS. 17 and 17a illustrate an exploded view of a heat sink
bonded to the heat pipe according to a preferred embodiment of the
present invention.
[0051] FIGS. 18a, 18b, 18c, 18d and 18e show a perspective view of
LED mounted on to various portions of the heat pipe.
[0052] FIGS. 19a and 19b illustrate packaged LED device on a
circuit board.
[0053] FIG. 20 shows a perspective view of a first circuit with a
center cut out for bonding of LEDs.
[0054] FIG. 20a shows a bottom view of the circuit of FIG. 20.
[0055] FIG. 20b shows a perspective of a second circuit with a
center cut out.
[0056] FIG. 20c shows a bottom side of the circuit of FIG. 20b.
[0057] FIG. 20d shows the first circuit of FIG. 20 and the second
circuit of FIG. 20b bonded together.
[0058] FIG. 20e shows the bottom side of the two bonded circuit of
FIG. 20d.
[0059] FIG. 21 illustrates a perspective view of the first circuit
of FIG. 20 with multiple LEDs.
[0060] FIGS. 22 and 22a show a ring assembled on top of the first
circuit of FIG. 20.
[0061] FIG. 22b illustrates the assembly of FIG. 22a with a TIR
lens/reflector.
[0062] FIG. 22c illustrates a bottom view of the assembly of FIG.
22b.
[0063] FIG. 22d shows a perspective view of the assembly of FIG.
22c with the first circuit.
[0064] FIG. 22e shows a perspective view of the assembly of FIG.
22d with a strengthening ring and the heat pipe.
[0065] FIG. 22f shows a bottom view of the assembly of FIG. 22e
illustrating alternate electrical connections.
[0066] FIG. 22g illustrates a complete assembly with the assembly
of FIG. 22d affixed to the assembly of FIG. 22f.
[0067] FIG. 22h shows an exploded view of the lens of the LED
including a concavity according to a preferred embodiment of the
present invention.
[0068] FIGS. 23a and 23b show an array of heat pipes inserted into
the circuit board.
[0069] FIG. 24 illustrates the LED array assemblies of FIG. 22g
being inserted into the circuit board assembly of FIG. 23a.
[0070] FIG. 25 shows the assembly of FIG. 22b and the assembly of
FIG. 22d with a protective outer sleeve.
[0071] FIG. 26a illustrates a perspective view of various parts of
the circuit board device prior to packaging and assembly with
LEDs.
[0072] FIG. 26b shows an array of LED packages according to the
present invention after the packages have been assembled and
singulated.
[0073] FIG. 26c shows an exploded view of one post-singulation LED
package according to the present invention.
[0074] FIG. 27 shows an expanded view of an individual LED package
of FIGS. 26a, 26b and 26c.
[0075] FIG. 27a shows a bottom-side view of the individual LED
package of FIG. 27 with the bottom layer including a highly
thermally conductive material.
[0076] FIGS. 28a and 28b show a side view of the individual LED
package of FIG. 27.
[0077] FIG. 29 shows a bottom-side view of the individual LED
package of FIG. 27 with the heat spreader.
[0078] FIG. 30a illustrates a perspective view of a flattened heat
pipe with LEDs.
[0079] FIG. 30b illustrates a perspective view of a flattened heat
pipe with LEDs.
[0080] FIG. 30c illustrates a perspective view of the heat pipe
bent around a finned sink.
[0081] FIGS. 31a and 31b illustrate a perspective view of an array
of LEDs bonded on a diamond substrate with a heat pipe according to
an alternate embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION:
[0082] The present invention provides high power LEDs and heat pipe
technology which allows for ultra-high power density packaging. The
ultra-high thermal conductivity of the heat pipe allows for
over-driving the LEDs by a factor of 4x, while maintaining junction
temperatures well within rated limits. Other attributes include low
thermal resistance submount, brightness-maintaining TIR reflector,
low cross-sectional area heat sink, and individually addressable
high-density chip array. These attributes facilitate the ability to
achieve high power densities, even without integral heat pipes,
which is especially useful for those applications that do not
demand ultra-high thermal performance.
[0083] The manner of bonding of the LED device to the heat pipe
component as in the present invention minimizes the physical space
requirements while taking advantage of heat pipes' unique rapid
heat dissipation capabilities. This allows much more closely spaced
LEDs operating at higher power and brightness. Some other features
of this heat pipe packaging for LED components include rapid
thermal response, variable heat flux, lightweight, high reliability
and requires little or no maintenance.
[0084] In one aspect of the present invention, there is provided a
novel means of cooling the light emitting devices preferably at
least one LED or organic LED ("OLED") or flexible OLED ("FOLED") or
Flip Chip LED ("FCLED"), or vertical cavity surface emitting laser
("VCSEL"). For the purpose of the invention, we will refer to the
LED, however, it is to be understood that other light emitting
devices mentioned or known in the art can be used as well.
Referring to FIG. 1, there is shown a single emitter LED 10
preferably manufactured by Lumiled Inc. It is understood the LEDs
from other manufacturers may be substituted. This particular
Lumiled emitter is referenced for example only. It has a "low dome"
lens on it in the drawing but a "high dome" (lambertian lense), no
lense, GRIN lense may be employed. Also, the wavelength in this
example is "Royal Blue" which is approximately 460 nm. Other
wavelengths from 200 nm to 11,000 nm may be used. The most
preferable wavelength range is 250 nm to 5,000 nm in the instant
invention.
[0085] The LED 10 in FIG. 1 typically includes a "clipped" anode 11
and cathode 12 legs to facilitate easier electrical connection with
a substantially round flexible hook-up wire bonded to the anode and
cathode with thermally and electrically conductive adhesive.
Element 14 is a highly conductive submount/slug between the anode
11 and the cathode 12, which is both thermally and electrically
conductive. A hole 13 with small threadlike protrusions is drilled
through the conductive slug 14 of LED 10. The threaded through hole
13 goes all the way through the highly conductive submount/slug 14,
preferably formed of copper. A plastic ring 15 holds the slug 14
and the LED lens in place. The inner diameter circumference of the
hole 13 is preferably within 0.010'' of the chip mounting
surface.
[0086] FIG. 2 depicts a device including an array of six LEDs 10
arranged desirably in semi-circle of potted polymer 20 sharing a
common coolant path. The polymer 20 is preferably a shore A
durometer UV thermal cure acrylic-urethane or silicone elastomer.
The inner semi-diameter is close to, or touching, the surface to be
cured or processed. It is understood that many different lensing
concepts in addition to the one depicted may be employed. The
polymer refractive index can preferably range anywhere from n=1 to
n=2, most preferred is 1.5. Different shaped domes of different
refractive indexes (or the same) as the polymer(s) may be used. No
domes, GRIN, etc. may also be used. The six emitters 10 depicted
are by way of example only. One single emitter to 100 for each row
may preferably be employed. Also, the radiation pattern does not
have to be substantially lambertian. Various focusing and/or
scattering treatments may be employed. For scattering a textured
surface on the polymer or polymers as well as bubble or beads
within the polymer matrix may be employed. The emitters 10 may be
arranged so that the optical radiation pattern is advantageously
employed on the desired area. Coolant (gas or liquid) 21 enters
into the device via channel 29 and is directed by channels 22 and
23 into the emitters 10 which have preferably lightly threaded
through holes 13 (not shown) to enhance thermal transfer by way of
boundary layer break-up. Channel 29 also serves as an exit channel
for coolant to exit the device. Channels 24, 25, 26 and 27 connect
one LED 10 from another serving to pass the coolant from one LED 10
to another. Channels 28a and 28b are 180.degree. return bends from
each LED 10 located at the end of the array returning the coolant
back to the channel 21. All these channels act as cooling channels
with coolant passing from channels to the holes 13 of the LEDs 10,
thereby cooling the LEDs 10 and high heat transfer rates can be
obtained.
[0087] Referring to FIG. 3 of the present invention, there is shown
six LEDs 10 in a mold cavity 30 preferably formed of aluminum. A
low melting point metal wire is encapsulated in polymer and then
melted out for a compact high power density array of LEDs or
VCSELs. Specifically, a low melting point solder wire that is
approximately 0.030'' diameter is fed through each of the
pre-drilled (0.033'' diameter) and threaded (0.9 UNM) holes 13 (not
shown) in the integral copper slugs 14 (not shown) of the LEDs 10.
Two wires are threaded through the holes in the LEDs and two ends
are formed into one 32 and the other two ends are also formed into
one 33 as shown in FIG. 3. It is important that the initial two
wires that form 32 do not ever touch the wires that form 33' They
may be UV tacked in place using 0P30 UV adhesive. Electrical
connections are then made which will be explained with reference to
FIG. 4. Referring back to FIG. 3 (after the electrical connections
are made in FIG. 4), a flexible potting adhesive/polymer 20 is
poured into mold 30 so that it covers all the aforementioned
parts/wire. The flexible potting adhesive/polymer 20 is UV cured
with an optional thermal cure at a temperature of 70.degree. C. The
cured polymer assembly is removed from the mold 30 and submerged in
a heated liquid to approximately 70.degree. C. and the wire is
melted out (it is best to first coat the wire with mold release).
Now a coolant path is formed between and through all the parts so
that during device operation, coolant can be injected through hole
34a of an inlet cooling tube 34 which passes through channel 28,
thereby cooling the LEDs 10 and it will come out hole 35a of an
outlet cooling tube 35 after it has circulated through and cooled
all the parts of the LED 10. It is understood that the cooling loop
could be either series or parallel. This ability of cooling of the
LEDs causes a substantially higher light output, hence fewer LEDs
need to be used.
[0088] FIG. 4 shows the device of the instant invention out of the
mold 30 for clarity and further showing the electrical connection.
The LEDS 10 are connected in parallel, however, it is understood
that the LEDs could also be connected in series. Also many (20
plus) individual small area emitter chips could be substituted for
the large area power LEDs. A stranded flexible "hook-up" wire which
is about 0.039'' in diameter and approximately 2'' to 3'' long is
pushed into and against the cathode tab and case of the LED. The
0.039'' diameter wire is bonded to the LED cathode tabs 42a-42e
with electrically conductive epoxy thereby connecting the LEDs 10
electrically. A similar treatment is done to the anode tabs
44a-44e. Finally, a 3' long wire 45 is bonded to the cathode wire
46 and a 3' long wire 47 is bonded to the anode wire 48. Again,
this is put into the mold cavity 30 in FIG. 3 prior to the UV cure
polymer 20 being poured in and cured.
[0089] FIG. 5 depicts six LEDs encapsulated in a polymer arch
(semi-circle). The electrical and coolant connection channels are
also shown. The power density on the surface to be cured or
processed can be addressed now. It should be from approximately 5
mW to 500 W per square cm, and this is in reference to all
embodiments described in this patent application. In the preferable
embodiment the power density is approximately 100 mW to 2 W per
square cm. In the most preferable embodiment the power density is
about 400 mW to 500 mW per square cm. It is feasible to have
excellent cooling characteristics in the present invention in
excess of several watt CW output power per light emitting device.
FIG. 5 shows inlet cooling tube 34 and output cooling tube 35.
These cooling tubes 34 and 35 can preferably be connected to a pump
50 and move coolant through the device and then to a reservoir or
chiller or heat exchange or all three 52. This process is referred
to as forced convection cooling in which the coolant (i.e., water)
being fed to the device via inlet cooling tube 34 is aided by the
force of a pump. The power leads 54 and 56 can preferably be
connected to a power supply or a battery 58.
[0090] In another aspect of the present invention, there is
provided a method for mounting and cooling LEDs and devices for
same that may be used for curing adhesives or composites and other
light source uses.
[0091] Referring to FIG. 6a, there is shown an LED curing device
60. The device 60 is preferably a hand LED curing device. The
device 60 includes a tubular wand body 62 made of plastic or metal
having two ends a wide end 62a and a tip end 62b which is bent.
Please note that the tip end 62b of the body 62 need not
necessarily be bent. LED 10 is located at end 62b of the body 62. A
heat pipe 64 extending through body 62 is bonded with glue or
solder inside the conductor slug 14 preferably of copper of the LED
10, although no cavity or hole need be made in the conductor slug
14. As shown in FIG. 6a, the heat pipe 64 may be modified to "neck"
down at the end 62b. Also a flattened heat pipe may be used and the
LED is bonded on top of the flattened end. An optional battery pack
61a and 61b may preferably be driven by a wall plug transformer not
shown, around middle portion of the body 62. A fan 66 that is
approximately 30 mm.sup.2 may be located at the end 62a of the body
62. A heat sink 68 preferably of Al or Cu is glued to "cold end" of
the heat pipe 64 between the fan 66 and the battery back 61a and
61b. The fan 66 is used to blow air over the heat sink 68 and
exhausted through ports (not shown) in the body 62 that most
components are mounted in. Switch 63 controls the electrical
current to the LED via wires (not shown) connecting the battery
pack 61a and 61b to the LED 10. The LED lense 10a is shown
surrounded by pambolic reflector 10b and optional additional lense
10c. The heat pipe 64 is a closed container into which a small
amount of liquid (working fluid, typically water) is injected under
vacuum. The inner walls of the container of the heat pipe 64 are
lined with capillary-action material (wicking structure). When a
portion of the heat pipe 64 is exposed to heat produced by LED 10,
the fluid in the heated portion i.e., hot end of the heat pipe 64
vaporizes picking up latent energy. The vapor flows to the "cold
end" of the heat pipe where the vapor cools and condenses releasing
latent energy and the condensed fluid is returned by capillary
action to the hot end. The heat pipe 64 serves as a heat engine
taking heat away from the LEDs 10.
[0092] FIG. 6b is an expanded view of the tip end 62b of the device
60 in FIG. 6a. The "pocket" 65 is shown wherein the heat pipe 64 is
milled, drilled, molded, etc., in the slug 14 of the LED 10 such
that it is only a few 0.001's of an inch greater diameter than the
heat pipe 64. High thermal conductivity epoxy is placed in the
bottom of the pocket 65 prior to the insertion of the heat pipe 64.
The operation of a heat pipe 64 is as discussed above, known by
those skilled in the art of heat transfer but has not been used
prior to this invention in a hand held LED device 60 for curing.
Also in the prior art, the heat pipe 64 has not been inserted into
or onto the slug 14 or submount of an LED 10 as shown, and also not
used for the purpose of mounting an LED 10 at the end of a wand 62
having a small diameter of around 8.5 mm O. Most LED slugs are
glued or soldered to a large PCB board or large, flat heat sink
which is incompatible with the application of the LED device 60
described herein. It is understood that the heat pipe 64 could be
soldered or glued to the LED "slugs" without the "pocket" 65 or a
separate heat pipe could be bonded to the LED.
[0093] In the above discussed embodiment of FIGS. 6a and 6b of the
present invention, the heat pipe 64 transports heat in a direction
that is not substantially perpendicular to the p-n junction of LED
10. The end of the device of FIGS. 6a and 6b that includes the LED
10 and reflector 106 mounted on the tip of the heat pipe 64 and
surrounded by a sleeve, is bent at 45.degree. about 7 mm from the
end of the device. The light is traveling away from the p-n
junction plane in a substantially perpendicular direction, (if it
were collimated,) but the majority of the length of the heat pipe,
and therefore the direction the heat is transported, is not
perpendicular due to the 45.degree. bend in the heat pipe 64. If
there were no 45.degree. bend (i.e. straight) the heat would flow
in a substantially perpendicular direction to the p-n junction.
[0094] FIG. 7 shows a liquid-cooled version of the LED hand held
curing device 60. By utilizing liquid cooling, the wand 62 (long,
slim tube) may be made flexible by using flexible liquid carrying
tubes. Wavelengths from 200 nm to 11,000 nm could preferably be
used including "white" LEDs. The LED body 10 is shown with an
attached tense 10a. The LED 10 is located at the end of wand 62
that is approximately 8.5 mm O and can be flexible, semi-rigid or
rigid. Coolant tubes 34 (inlet) and 35 (outlet) are bonded to an
optional threaded through the hole 67 in the slug of the LED 10. In
this way coolant is passed through the LED 10 at approximately 2
psi to 50 psi for the purpose of cooling the LED die (not shown,
but bonded to one end of the conductor slug 14). The coolant tubes
34 and 35 are attached respectively to the pump 50 which supplies
the coolant (i.e., liquid) and a finned heat exchanger 52, which
receives the heat. Fan 66 is the drive electronics for pump 50. Fan
66 passes air over the external fins of heat exchanger 52 and the
air is discharged through ports (not shown) in the molded plastic
housing of the body 62. No electrical leads are shown for drawing
clarity. Battery pack 61a and 61b is shown. The device may be
operated strictly from batteries or may have a cord to a wall
mounted transformer. The purpose of the liquid cooling is to be
able to remove the heat generated by the LED die 10 that is in a
very small area and "pump" the waste heat to a larger area, the
heat exchanger 52 via the heat pipe 64. Using this technique, LEDs
may be driven at higher operating currents and output power than if
they were mounted to a flat heat sink and/or PC board (PCB).
Additionally, it is difficult to have a heat sink of PCB out at the
end of an approximately 8.5 mm O diameter wand that is needed to
get into "tight" spaces in an electronic assembly glue curing
application or a patient's mouth for curing or whitening. Also very
important, is the fact that it is easy to make "wand" that is
flexible if liquid cooling is used to transport heat at high flux
from one end of the wand to the other.
[0095] FIG. 7a is an expanded view of FIG. 7 wherein the inlet and
outlet tubes 34 and 35 respectively, are more clearly shown. These
tubes are available from HV Technologies (North Carolina) with a
thin spiral or coil wire in the wall for kink resistance.
90.degree. bent tubes 71 and 73 are glued into the through hole 67
in the conductor slug 14 to pass the coolant from the inlet tube 34
into the LED 10 and similarly to send the coolant out of the LED 10
into outlet tube 35. The approximately 8.5 mm O tube wand 62 may be
rigid or flexible depending on the application. Curing
industrial/photonic adhesives could be accomplished by using a
flexible "mono-coil" type outer tube that would carry the coolant
tubes 34 and 35 and electric wires to the LED 10 at the end. The
"mono-coil" would then serve as a sort of replacement for a
light-guide for curing equipment. The LED 10 at the end could also
be replaced by an edge emitting laser diode or VCSEL. The LED 10
may be driven at higher currents than would be possible with just a
heat sink, and is especially useful in small, contained areas where
it is difficult to cool high power density devices and areas where
a flexible light source is advantageous.
[0096] FIG. 7b is an expanded view of another embodiment for the
instant invention. Here the LED 10 has a coolant inlet hole 75 in
the center of the conductor/slug 14 and a feeding inlet tube 34 is
shown. The inlet hole 75 is bi-sected by one or more outlet holes
75a and 75b near the bottom or end of the hole 75. This arrangement
allows for lower thermal resistance cooling as the inlet hole 75
serves to "impinge" coolant on the area of the conductor/slug 14 at
the bottom of hole 75 that is immediately below the LED "die" (not
shown for clarity). The outlet holes 75a and 75b (two more outlet
holes are not shown for clarity) allow the heated coolant to escape
with minimal back pressure where it is returned via pump 50 to the
heat exchanger 52 (or chiller). It is understood that all these
embodiments do not necessarily have to be hand held. A "5 W" LED
may preferably be driven with two to six times the current with
this technology. Multiple arrays or single LED 10 (or laser diode)
units may use the same cooling techniques described in the instant
invention for static or stationary wall or bench-top units for may
applications where a light source of high intensity in a tight
space is required beyond just curing.
[0097] In an alternate embodiment of the present invention, there
is provided a LED device wherein the LED die is mounted and/or
bonded to the tip of a heat pipe, where the heat pipe may have the
function of an anode or cathode in addition to its heat sinking and
transport functions. This LED/heat pipe invention has broad
applicability when used with UV or visible LED packages and/or
individual die or combinations of each such as in UV lamps for
curing adhesives and various other applications.
[0098] Referring to FIG. 8, there is shown the heat pipe 64 having
an average range of the diameter of preferably between 3 and 6 mm
and average length preferably ranging between 25 mm and 500 mm. The
LED chip (or die) 10 is shown bonded to the tip of the heat pipe
64. The heat pipe 64 may be flattened to accommodate the flat die.
It is understood that packaged LEDs, i.e., presoldered to heat
sinks or slugs could also be used. If the conductor slug 14 is used
it may have a female contour in it to accommodate the end of the
heat pipe 64. The heat pipe 64 itself may be the electrically
charged anode 11 and a wire bond may be made on top of the LED die
as shown in FIG. 8 to make the cathode wire connection 12. These
functionalities could also be reversed. In this manner, the heat
pipe 64 provides an electrical connection to the LED 10 in addition
to cooling the same. The heat sink 68 may be bonded to the
condensing end of the heat pipe 64 and an optional fan 66 to blow
air serving as the cooling medium over the heat sink 68.
[0099] In FIG. 8a, the heat pipe/heat sink is shown with multiple
LED dies 10. They may be connected in electrical series or parallel
or be individually addressable. The dies 10 may emit one or more
centered wavelengths. A shaped, molded or potted polymer or glass
or ceramic lense 81 is shown and it may encapsulate the LED dies 10
and is preferably made from a UV degradation resistant polymer. The
arrows 82 depict the light emission from the LED(s) 10. Element 84
depicts a vapor cavity that extends down the center of the interior
of the heat pipe 64. It is substantially parallel to the outside
diameter sides of the heat pipe 64. The LED cathode and anode
surfaces (p-n junction) are substantially perpendicular to the heat
pipe vapor cavity 84 axis of the heat pipe 64 which is
substantially straight and unbent. The heat pipe 64 may be bent in
may different shapes for many lighting applications.
[0100] FIG. 9 is a hand held LED curing device 60 having a plastic
housing that incorporates at least one LED die 10 or at least one
pre-packaged LED device that is bonded to the evaporating end of a
heat pipe 64. Cathode wire 12 is bonded to the cathode side of the
LED die (not shown). Element 20 is a transparent material that is
preferably a UV resistant potted or molded polymer as discussed and
shown earlier in FIG. 2. Again, element 63 is the electrical on/off
switch. Element 92 is a surface including a gel material that
preferably contains hydrogen peroxide and also preferably a
photosensitizer, photoinitiator, or chromophor that the actinic
light from the LEDs "activate". Element 94 is a phase change
material that is preferably a paraffin material which is placed
between heat pipe 64 and the rest of the part of the device outside
the heat pipe 64. When the LEDs 10 are turned on, the waste heat
will flow down the heat pipe 64 and melt the paraffin 94 after a
predetermined approximate time. The paraffin 94 will melt, i.e.
change from solid to a liquid and expand and "break" the electrical
circuit that is formed between the batteries 61a and 61b (which may
have a different orientation than shown, i.e., upside down) the
electrically conductive piston 96 and spring 98, the electrically
conductive (preferably water filled copper) heat pipe 64 (which, in
essence becomes the anode), the LED die 10 (or pre-packaged LED
device) and the cathode wire 12. This phase change will help
conduct heat away from the condensing end of the heat pipe 64. In
this case, instead of fan, paraffin 94 will absorb heat from the
heat pipe 64. Furthermore, paraffin 94 absorbs heat energy without
raising temperature when it melts and cools down. Again, this
process works best for short duty cycle application. The novelty of
this embodiment is the ability to rapidly transport heat from the
LED 10 through a heat pipe 64 past the batteries 61a and 61b and to
a forced convection cooling (or also non-forced convection in
another embodiment). For short duty cycle applications the heat
pipe 64 (preferably porous) can be surrounded by a phase change
material, such as paraffin, to absorb heat as will be described in
greater detail with reference to FIG. 9 below.
[0101] FIG. 9a shows an adhesive curing device embodiment of the
present invention. As in other embodiments, a CVD Diamond heat
spreader 230 as shown in FIG. 19, is optionally positioned between
the LED 10 and the heat pipe 64 in the wand tube 62, which is
anodized. If the anodized wand tube 62 is not used, the heat pipe
64 can preferably be covered with .about.0.002'' thick polyester
shrink wrap. Here, the heat pipe 64 functions as the anode 11 to
the LED 10. LED 10 is optimally soldered to the CVD heat spreader
230 which in turn is conductively glued to the end of the heat pipe
64. Cathode wire 12 is bonded to the LED 10 and the parabolic
reflector 10b. As in other embodiments, a phase change material 94
(usually paraffin) can preferably be communication with the heat
pipe in order to further dissipate the heat being generated by the
LED 10 and transported along the length of the heat pipe 64. Here,
the phase change material 74 is also in communication with copper
wool 95, which further dissipates heat throughout the phase change
material 74 due to the high thermal conductivity of the copper
wool. This embodiment is shown to include lithium batteries 96 but,
as in other embodiments, power could instead be supplied to the
device of the present invention using a power cord of some
kind.
[0102] FIGS. 9b and 9c depict an LED array for use typically in
ultraviolet curing applications. This embodiment is composed of a
number of LEDs 10 disposed upon a slug 14 with a blind hole into
which the heat pipe 64 is fixably and/or detachably inserted. Fins
208 as more clearly shown in FIG. 12a are optionally included. Fins
208 are preferably bonded with solder 110 or a high thermal
conductivity glue. The fins 208 further dissipate the heat
transferred from the LED 10 to the heat pipe 64. The LEDs 10 are
attached to the slug 14 via bond pads 214 via bond wires 212 as
more clearly shown in FIG. 14b, and may be electrically powered in
series, in parallel, or as individually addressable entities. The
number of LEDs 10 that may be used in this type of an embodiment is
limited only by the size of the slug 14 and the heat transport
capacity of the heat pipe 64 in combination with any other heat
dissipation mechanism (such as the fins 208). It is easy to
envision an embodiment wherein the single heat pipe 64 is replaced
by a number of separate heat pipes of similar or varying size, all
of which are in communication with any number of LEDs 10 via a
single slug 14. It is noted that two fins 208 are shown but more
than two fins 208 are possible. Positive 97 and negative 97' gold
contacts wrap around the edge of the slug 14. Also note that LEDs
10 are shown in series, but may also be in parallel.
[0103] In another embodiment, the device of the present invention
is preferably used UV curing applications where the heat pipes are
located in different orientations wherein the hot end has the LEDs
and the cold end is in a heat sink. The heat pipe in these
embodiments is somewhat analogous to the function of a light pipe
or lightguide except that it transports heat instead of light, and
the source of light is at the output tip of the heat pipe.
[0104] In an additional aspect of the present invention, there is
provided a device used to cure UV inks and coatings and adhesives.
The device includes an array of large area UV (or visible) LEDs
that are mounted on heat sinks) which are cooled by an array of
(circular or flat) heat pipes that are themselves cooled by one or
more fans as described in detail below.
[0105] Referring to FIG. 10 there is shown a device 100 having an
array of LEDs 10 which are soldered to one or more heat sinks 68,
preferably formed of copper. The heat sinks 68 are electrically
isolated from each other by thin strips of Kapton 101 or other
non-conductive material that have thin layers of adhesive on both
sides 102 and a layer of copper foil 103 sandwiched in between.
Each LED 10 has a wire bond 104 that attaches to the copper foil
103 of the heat sink 68. All copper foil layers 103 are brought to
form the cathode common electrical connection. For every
approximately 11 mm of electrode length there are three
approximately 3 mm O blind holes 107 drilled in each electrode 109
(only one of 90 are numbered). An approximately 200 mm long by 3 mm
O heat pipe 64 is inserted with an electrically conductive compound
in each hole 107. The heat pipe condensing (cold) ends are inserted
in a top plate 108 and attached with an electrically conducting
compound such as conductive epoxy. This top plate 108 serves as the
common electrical anode connection. Depending on the design of the
LEDs the polarity of the electrical connections can be reversed or
modified. The current path as shown, is through the top plate 108,
down the heat pipes 64, through the electrodes 109, through the
LEDs 10, through the wires 104, and out through the copper foil
103. It is understood that electrodes 109 could be monolithic with
circuit "traces" for a cathode connections, or they could be
electrically isolated from the heat pipes 64 and the LEDs 10 could
be bonded directly to the heat pipe tips (ends), which is most
applicable if there is a through hole (rather than blind hole) in
electrodes 109.
[0106] Glass may be ion beam sputtered over the LEDs 10 for index
matching purposes. Gold may be electroplated onto the copper
surfaces for ease of wire bonding and die bonding. A single point,
diamond-turned, fly-cut pass may be made over the bonded three
electrodes 109 to create a small, flat, die-bonding surface.
Lastly, a glass plate (cover slide) may be placed over emitting
LEDs 10 to protect them. The glass may be hermetically seated and
have a sub-wavelength structure on it for anti-reflection purposes.
Also, flat plates (thinner than the top plate) can be installed to
increase surface area. Preferably one or more 100 mm fans on each
side of the heat pipe array cool the heat pipes in a push me-pull
me arrangement. The optional flat plates can be oriented parallel
to the airstream (from fan(s) or blower(s)). It is to be noted that
in FIG. 10, the LED 10 repeat down length of device in groups of
six and only 18 LEDs of approximately 540 LEDs are shown for
drawing clarity. However, different quantity and sizes of LEDs 10
may preferably be used.
[0107] The heat pipes are preferably oriented vertically so that
the wicking action is enhanced by gravity. The heat pipe (or heat
pipes) may have an additional bonded heat exchanger (or heat sink)
with fins surrounding it (for added surface area) or it may be
stand-alone (no bonded heat sinks or fins). When an array of heat
pipes are employed each heat pipe essentially becomes a "pin" in a
so called "pin-fin" array heat sink to dissipate thermal energy
from the LEDs over a large area. The heat is taken in by the heat
pipe 64 at the end where LED is placed and spread out in the entire
surface area of the heat pipe which preferably is between 2-8 mm in
diameter. In the preferred embodiment the heat pipe transports the
heat away from the p-n junction of a diode in a direction that is
substantially perpendicular to the junction. It must be stressed
that because heat pipes can be bent in most any shape or form, it
must be understood that the heat pipe could transport heat in a
direction that is not substantially perpendicular to the junction.
The vapor cavity in the heat pipe may have only a portion that is
nearly perpendicular or nearly parallel to the p-n junction. Also,
only a portion may be nearly perpendicular or nearly parallel to
the emitted light from a light emitting device. The aforementioned
word "nearly" may be substituted with "substantially". Also, the
term "heat" can be used interchangeably with "waste heat", "thermal
energy", etc. One or more heat pipes (arrays) cooling one or more
light emitting devices (arrays) may be of small (preferably less
than 2'' square inches) of large (preferably more than 2'' square
inches) dimensions thus used for a variety of medical and
industrial uses such as curing adhesives. For curing adhesives, an
apparatus similar to FIG. 10 is ideal for all applications that a
microwave (electrodeless) lamp is currently used for.
[0108] The inner diameter ("ID") along the length of the heat pipes
is comprised of a hollow vapor cavity 84 as shown earlier in FIG.
8. The light from the LEDs is generated at the "p-n" junction which
is epitaxially grown in layers on a preferably GaN wafer which is
diced into chips. The chips may be bonded to the electrodes "p"
side down. Other wafer types are SiC and sapphire. Other means for
forming p-n junctions other than epitaxial may be employed.
Different styles and sizes and manufacturer of LEDs may be
substituted for those described and depicted in the figures. As
discussed earlier, the cold ends of the heat pipes 64 can be cooled
by a coolant (liquid or gas). The electrodes 109 could also be
liquid cooled and have internal channels therein.
[0109] In an additional aspect of the present invention, there is
provided a novel LED packaging scheme and process for making same
which results in a very simple, inexpensive and compact package.
This advantageously allows the rapid transport of thermal energy
away from a high energy density heat source such as an LED chip, to
a very large surface area heat sink while minimizing the size of
the heat source and the frontal, cross-sectional area of the heat
sink surrounding it. This fast thermal transport most preferably
allows the operation of LED chip(s) at a threefold to fivefold (or
more) increase in power over standard packaged chips while keeping
the operating (junction) temperatures well within rated limits.
Also, since brightness can be defined as the "power per solid cone
angle of light," when increasing the chip power while maintaining
the same cone angle, brightness is increased. This invention
combines high brightness LED chips and highly effective heat pipes
in a novel packaging scheme and process for making same which
results, not only in the ability to operate the LEDs at
unprecedented brightness, but also unprecedented cost per watt.
Essentially, one chip is outputting the power of three to five
chips (or more), not in the area of three to five chips, but in the
area and cone angle of a single chip, with minimal heat sink area
consumed around the periphery of the chip. This small frontal
cross-section results in the ability to use compact and efficient
lenses and reflectors that can take advantage of the chip's
brightness in the most efficient, effective and space saving way
possible. The devices depicted in this application may contain at
least one infrared ("IR") die and the emitted light may be used for
curing adhesives or coatings by heat instead of the more common UV
or visible photoinitiated chemical reaction. The LEDs may be used
individually or in array form with one or more heat pipes either in
a unit that is hand-held, fixed, or some combination of both. The
present invention most preferably combines mainstream IC packaging
technology, circuit board technology, and power LED technology in a
novel configuration that provides solutions to a broad array of
light curing applications and devices.
[0110] These applications and devices advantageously utilize the
primary attributes of the technology which is high brightness and
power in a very compact and cost effective package.
[0111] Referring to FIG. 11, there is shown a LED 10 bonded to the
tip of at least one heat pipe 64. The LED(s) 10 is(are) affixed to
the heat pipe 64, by a solder or an adhesive 110 such as indium or
tin, lead/tin, or gold/tin that is preferably electrolitically
deposited to the heat pipe 64. The solder process my use flux or be
"fluxless". The square (or other geometrical shape) is defined by
an exposed and developed area of the electrophoretic photoresist
111. The flux process must be compatible with the photoresist. This
photoresist layer 111 also acts as a dielectric (insulating) layer.
The heat pipe 64 is adhesively bonded to the inner diameter of tube
112 comprised of conductive material, preferably aluminum. The tube
114 may be anodized and it can act as the cathode to the device
when the wire 113 is bonded or mechanically affixed to it in an
electrically continuous manner. The diamond-turned or injection
molded elliptical or parabolic total internal reflection ("TIR")
reflector 10b is placed over the LED 10. It has an index of
.about.1.53. The TIR reflector may be a Dielectric Totally
Internally Reflecting Concentrator (DTIRC), a Compound Parabolic
Concentrator (CPC), an Elliptical Concentrator (EC), a Compound
Elliptical Concentrator (CEC), or a Compound Hyperbolic
Concentrator (CHC). All of these may have flat or curved exit
apertures. If curved, an aspheric surface may be employed. If flat,
a diffractive surface may be employed. These reflectors also have
the unique ability to mix multiple wavelengths that may be emitted
from multiple light emitting devices into a homogeneously mixed
beam of light. We refer to this unique attribute as a "color mixing
TIR" reflector. The space for the LED 10 is an integrally molded,
concave female preferably hemispherical surface 114 that is filled
preferably with a high index silicone polymer or other transparent
material. This high index polymer may preferably be .about.1.6 or
greater. The refractive index between reflector 10b and the surface
114 can preferably add optical power and bend light rays to stay
within the critical angle for TIR. An anti-reflection (AR) coating
may be ion beam sputtered (or other process) on the plane (or
curved) emitting surface of the TIR reflector 10b. The vapor cavity
84 of the heat pipe 64 is shown and is only approximated. In the
preferred embodiment of the invention, the heat pipe 64 of a
conductive material, preferably copper, may act as the anode
(although it could be cathode or even electrically neutral or some
combination of all three). A conduction path can be traced from the
batteries (not shown), through the heat pipe 64, through the solder
110, through the LED 10, through the wire 113, into the insulated
sleeve tube 112, and back to the batteries (not shown) through the
electrically conductive heat sink(s) (not shown) after passing
through a switch (not shown). The wire 113 is bonded to the inner
diameter of the insulated sleeve 112 with a small dot of
electrically conductive adhesive 115. FIG. 11 depicts only one LED
die 10 but multiple LEDs 10 at the same or multiple or varied
wavelengths may be employed. The dielectric layer 111 electrically
insulates the electrically active heat pipe 64 from the
electrically active sleeve 112. The sleeve may be desirably
anodized aluminum with an unanodized spot underneath glue dot 115
so as to form a current conduction path from the wire 113 to the
tube 112. A small gap 116 may or may not exist and it may be filled
with a material such as thermally conductive or thermal insulating
adhesive. This may be advantageous if the tube 112 and heat pipe 64
are bent near the tip at an angle of approximately 30.degree. to
45.degree.. The wick structure 127 shown in FIG. 11f is preferably
small, axially extruded grooves but it may be a screened-wick or
sintered (powdered) metal wick. An AR coating or sub-wavelength
structure may be employed on the exit aperture 118. LED light
emission is depicted by arrow(s) 117 which are shown undergoing TIR
at the reflector wall/air interface. Light emitting from aperture
118b is depicted by arrow(s) 118a. The light 118a is then impinging
on the example application of two blocks 119 and 120 with light
cure adhesive. The light is of sufficient intensity to "cure" the
adhesive 121 and the two blocks 119 and 120 will be affixed
together by the cohesive strength of the adhesive 121. The adhesive
curing device in FIG. 11a may be used to cure "surface coatings"
such as UV clear coats, conformal coatings, etc. The device may
also be used to cure "solid-body" objects such as those found in
stereolithography processes or casted or molded objects. Examples
of these "solid-body" objects are the bases and/or ear molds for
hearing aids as well as countless applications involving
photochemical curing of molded object in transparent or open
molds.
[0112] The LED 10 bonded onto or near the tip of at least one heat
pipe 64 simultaneously maximizes the rate of heat transfer away
from the LED chip 10 and minimizes the frontal cross-sectional area
of the heat sink 68 or submount or heat exchanger. The light
emitting 82 from the LED junction(s) 10 preferably travels in a
direction that may be substantially opposite to that of the waste
heat that is transported axially down the length of the vapor
cavity 84 of the heat pipe(s) 64 and away from the junction(s). The
light from the device may emit into a shaped volume that is
substantially opposite to a shaped volume of material which the
heat is dissipated in or transported to. The plane that separates
these two volumes may be the p-n junction plane (the transition
boundary between p-type and n-type materials in a semiconductor)
and/or it may be the plane that the epitaxial p-n junction is
bonded to. Because the heat preferably is not distributed over a
large radial distance, but rather a large axial distance, close
spacing of LED or LED assemblies (or an array of assemblies) as
well as their associated optical systems (lenses, reflectors, etc.)
and heat exchangers may be spaced closely together. This results in
high power LED devices and/or assemblies that are more compact,
lightweight, and inexpensive to manufacture than conventional
devices.
[0113] It has not been shown in the previous art to place a heat
source such as a diode (or other high energy density semiconductor
device) on the tip of a heat pipe because it has been considered
sub-optimal. The reason for this is that it has been thought to be
best practice to place the heat pipe into a larger heat sink with
the heat source bonded to this heat sink so as to allow the heat
sink to spread the heat around and along a larger surface area of
the heat pipe. The problem with this is that there is generally
more material between the heat source and the heat pipe and the
heat must travel through this excess material to reach the heat
pipe itself, as well as travel around the circumference of the heat
pipe. Also, the heat will spread both toward and away from the cold
(heat exchanger) end because the source is not at the tip of the
hot end. All this imparts a great deal of thermal resistance
between the heat source and the heat exchanger. Also, if a small
high power density device (like a diode) is placed near the wall of
the heat pipe it can "dry-out" i.e., deplete the wick structure of
fluid of a localized area. By placing the die, such as a
light-emitting diode 10, on the tip of the heat pipe 64, as shown
in FIG. 11, there often is not a functioning wick structure
immediately below the die, and so dry-out may be less of an issue.
Most importantly, a full 360.degree. heat spreading around the heat
pipe 64 is easily accomplished in a radially and circumferentially
uniform manner, thereby decreasing the likelihood of dry-out as
thermal energy moves along the wick structure. The LED 10 (heat
source) is at the hot (evaporating) end of the heat pipe 64 at the
furthest possible point from the cool (heat exchanger) end of the
heat pipe. The cool end is also known as the "condensing" end.
Additionally, if the heat pipe 64 is at an angle so that the heat
source at the tip is closer to the ground than the cool (heat
exchanger) end, then the heat source has the benefit of being fed
coolant (i.e., water) that is aided by the force of gravity as
discussed above. This coolant may pool or form a reservoir that is
a ready source for the wick structure due to evaporation that
consumes liquid from the wick structure. This process decreases the
likelihood of the dry-out phenomenon. Lastly, by bonding the heat
source directly to the heat pipe 64 without a heat spreader or heat
sink there is one less thermally resistive bond line for the
thermal energy to travel through before reaching the heat pipe
64.
[0114] FIG. 11a is similar to the structure shown in FIG. 11,
further including electrically conductive washer 122 that wedges
the wire 113 against the inner diameter of the sleeve 112.
Incidentally, the sleeve 112 may be plastic with a metal conductive
strip adjacent to washer 122 or it may be a conductive metal with
an electrophoretic coating to protect it from the environment. The
electrophoretic coating would have a bare spot where the washer 122
contacts the sleeve 112. Similar to FIG. 11, light emitting from
the exit aperture is depicted by arrow(s) 118. In the example
application the light 118 is shown impinging on surface mount
device 123 and its lead with solder bump 124 as shown in FIG. 11a.
The light may have an IR wavelength (could also have UV, visible,
or other). In this application, the solder bump 124 will reflow
from the heat of the light 118. The solder bump 124 may instead be
a light cure adhesive bump or a heat cure adhesive bump, and may or
may not have a solder or flux component in it. The LED light (as in
all embodiments) may instead be emitting from a laser diode. If the
light is emitting from a laser diode, it may preferably be focused
to a very small spot. A visible component of light (perhaps from an
LED) would be preferred if the actinic light was invisible (i.e. UV
or IR). This nearly point source of light may be used for other
applications, as well as for heating, surface modification (i.e.,
ablation, etc.) or photo-chemical reaction, etc.
[0115] FIG. 11b depicts another embodiment of the invention for
mounting the LED(s) 10 in the center of the heat pipe 64. The
Kapton or other non-conductive material ring 125 is coated
preferably with copper on the top surface 126 of the ring 125. The
ring 125 has a shape, preferably a square shape cut out in the
center which allows for proper die positioning when an external
sleeve just bigger than the heat pipe 64 diameter is positioned
around it. A solder reflowing operation may be undertaken and when
the solder 110 (that may be already coated on the bottom of the die
10) is reflowed, the ring 125 will keep it centered on the heat
pipe 64. The wire 113 that is bonded to the center of the die 10 is
also bonded to the top 126 of the ring 125. The conductive copper
(or other conductive material) on the ring 125 has perforations
125a that allow it to bend into a myriad of "fingers" when a
conductive sleeve 112 in FIG. 11c is brought into contact with it,
thereby forming a current conduction path from the heat pipe 64 up
through solder 110 and die 10, through the wire 113 into the copper
surface of the LED 10 and then into the sleeve 112 of FIG. 11. An
adhesive such as glue 115 may exist below or on ring 125.
[0116] FIG. 11c is similar to Drawing 11b, except that the
conductive sleeve 112 is shown making contact with the conductive
ring 125. The sleeve 112 may be anodized aluminum except a small
area may be masked during the anodizing operation to allow an
exposed electrically conductive area that can contact ring 125.
Instead of anodizing, an electrophoretic coating may also be
employed.
[0117] FIG. 11d further depicts the heat pipe 64 with the solder
110 and the LED die 10 on top and in the center of the heat pipe
64. The wire 113 is bonded to the center of the die 10 and also is
bonded to the top of the copper strip or Kapton ring 125 that has
an adhesive section 115 between it and the heat pipe 64. The
current connection between the die(s) 40 and the sleeve 112 is made
when the copper strip/Kapton ring 125 contacts the sleeve 112 which
is connected in a current conduction path to the battery(s) or
power supply (not shown). The die 10 may be centered by a manual or
computer driven die bonder or a pick and place machine, with or
without machine vision. This is true with all die(s) depicted in
this invention.
[0118] FIG. 11e shows the sleeve 112 as a separate heat sink 68.
The LED 10 is shown with attached wire 113 mounted on the tip of
the heat pipe 64. The sleeve 112, the heat sink 68 and the heat
pipe 64 may preferably be electrically isolated from each other and
may be any polarity, or neutral, or a combination of polarities.
They may also carry electrical traces that can be individually
addressable and traced to individual dies.
[0119] FIG. 11f further shows the heat pipe body 64 with sintered
wick structure 127. In this application, the wick structure 127 is
shown with a full coverage of operation wick structure, not only
along the inner diameter circumference walls, but also completely
covering the tip body surface under the die 10 at the hot end of
the heat pipe 64 shown in this drawing. The solder 110 or
conductive epoxy is shown as well as wire 113 which is bonded to
die 10. If a thermosetting adhesive exhibiting a high thermal
conductivity such as one disclosed in U.S. Pat. No. 6,265,471 is
used, it is preferred to first deposit silver (Ag) to both the die
10 and surface of the substrate (or any two contacting surfaces) it
is bonded to as this greatly decreases the contact thermal
resistance (interfacial resistance) because the patented
formulation of the adhesive allows fantastic heat transfer between
silver-silver connection and worse performance with contact between
other material.
[0120] FIG. 12 shows an exploded view of the LED/heat pipe assembly
as it is assembled into one or more heat sink 68 with battery pack
61a/61b. The heat sink is actually two electrically isolated heat
sinks 68a and 68b that when "shorted" by switch 63 complete an
electrical circuit from the positive battery lead that contacts the
tip opposite the LED 10 of the copper heat pipe 64, through the LED
10, solder and wire path 201, through the sleeve 112 into the cone
section of the heat sink 68, through the closed switch 63 into the
bottom section of the heat sink 68, through the battery pack
61a/61b and into the cathode end of a battery (or batteries) 202.
The two heat sinks 68 may preferably be anodized aluminum or some
other conductive material that may be electrophoretically coated
with a non-conducting polymer. The two heat sinks 68 may be bonded
together with non-conducting adhesive (not shown) and the heat pipe
64 through hole 203 may be filled with an electrically insulating,
but thermally conductive compound. The heat pipe/sleeve assembly
may be held in place in the heat pipes by a simple set screw 204.
The hole 203 is simply a long hole through each heat sink 68a and
68b that accommodates the heat pipe 64 and it may or may not have a
dielectric layer. The fins 218 shown in FIG. 12b on the heat
sink(s) 68 may be either radial and/or at an angle in relation to
the heat pipes and /or they may be axially disposed.
[0121] The light from the LED 10 emits through a transparent
dielectric concentrator 205. The light emission direction is shown
by arrows 206. The most preferable embodiment contains one high
power LED 10 on the end of the heat pipe. However, multiple LEDs 10
can be used at one or more centered wavelengths. Also the LED(s)
may preferably be mounted on a small heat sink or heat spreader
that is in turn mounted near or on the end of the heat pipe.
Multiple heat pipes may also be employed. Individual or arrays of
lenses may also be employed. If the lense is a reflector it may be
faceted or it may have smooth walls. It may be totally internally
reflecting or it may be a metallic or dielectric coated wall or
polished wall reflector.
[0122] FIG. 12a shows the light emitting diode 10 through
reflector/lens 10a/10b. The sleeve 112 (not shown) is electrically
connected to heat sink 68a. Switch 63 completes the electrical
circuit between electrically conductive heat sink 68a and heat sink
68b. Battery pack 61a/61b is also electrically active (current
carrying) and its function, beyond containing the batteries is to
connect the cathode end of the battery 202 in the heat sink 68b.
Also, O-ring 207 is shown and is attached at the connection of the
heat sink 68b and battery 202 to seal out water and to provide a
smooth (tactile) feel during the thread rotation action. The light
emitting device 10 shown in to FIG. 12a may preferably be powered
by an electric cord. The device may be convective cooled through
the many fins 208 as will be shown in FIG. 12b. The device may have
a gravity or tilt-type shut-off switch as will be shown in FIG. 12c
within the handpiece shown to prevent the device from being
operated in a substantially non-gravity aided wick orientation.
Furthermore, the device may further desirably have the heat pipe 68
and sleeve 112 together bent at an angle.
[0123] FIG. 12b depicts a solid-state lighting application wherein
at least one LED die 10 is bonded to at least one heat pipe 64
which is then further bonded to at least one or more heat sinks 68.
In the preferred embodiment, the heat pipe 64 is oriented
substantially down or vertical with the LEDs 10 being at the lowest
point near to the ground. In this way the heat pipe 64 is said to
be aided by gravity. The LED/heat pipe assembly is the same
assembly depicted in FIG. 11a, except that the heat pipe 64 is
shown bonded in the somewhat spherically shaped heat sink 68 that
has fins 208 that may be machined, or most preferably molded in
place. If it is molded it may be thixoformed, die cast, permanent
molded, or other similar process. These processes facilitate the
high volume and low cost that is needed for a solid-state lighting
product. All heat sinks 68 or heat exchangers 76 in this
application may be molded and may be made from an alloy of
magnesium. It is understood that multiple LED dies 10 at multiple
centered wavelengths and with heat pipes 64 (that may be bonded in
one or more heat sinks) may be used. The LEDs 10 may be
electrically individually addressed and individually modulated or
they may be in electrical series, parallel, or other electrical
connection. Threads 209 on top portion of the heat pipe 64 may be
an electrically "active" component and they may facilitate an anode
or cathode or ground connection. If the heat sink 68 is
dielectrically coated and the threads are uncoated, they may be of
monolithic or at least of electrically continuous design.
Electrical contact 210 above the threads 209 which is preferably
the cold end tip of the heat pipe 64 is either the anode cathode or
ground, but is of preferably the reverse polarity of the threads
209 and electrically isolated from it. An electrical circuit could
preferably be placed between electrical contact 210 and the power
source such as within the threaded area 209 that may step up or
step down current or voltage. This circuit may be present in any
embodiment in this patent application. The device depicted in this
drawing could be threaded into a heat sink 68 that may be
electrically active and could absorb heat, as well as supply
electricity.
[0124] FIG. 12c depicts the front section (light-emitting end) of
the light source embodiment of the present invention. This light
source may be portable and fit easily in the human hand. Again,
like most embodiments in this patent application, a heat pipe 64
(or heat pipes) is (are) used to distribute heat rapidly away from
an LED 10 (or LEDs) to much larger fins on a heat sink 68. A
reflector 10b is shown and this reflector may be made adjustable in
that the cone angle of light 211 may be adjusted by the operator or
during manufacture of the light source. Wire bond 212 is shown
running from the die(s) 10 to the heat sink 68. The heat sink 68
may be anodized aluminum thereby shielding the operator form
potentially adverse electrical shock because anodize (aluminum) is
a very good electric insulator. The wire bond 212 obviously
contacts a spot on the heat sink 68 that is not anodized (masked
during manufacture). The light source 211 may preferably have a
rotating battery pack that opens or closes the electrical circuit
when rotated approximately one-quarter turn.
[0125] FIG. 12d shows the entire light source whereas FIG. 12c
showed only the front section referred as the "nose" section. The
LED light is shown emitting light out of the nose by arrows 211.
Heat sink(s) 68 are preferably connected electrically by switch 63.
The battery pack 61a/61b preferably is affixed to heat sink 68 by
mechanical threads (not shown) in an electrically continuous
manner.
[0126] FIG. 12e depicts a heat pipe 64 and surrounding sleeve 112
bent at an angle, which could be useful to many of the embodiments
described herein.
[0127] FIG. 13 shows the embodiment of the invention wherein
multiple LEDs 10 are bonded to at least one heat pipe 64 and rested
on a circuit board 216. The LEDs 10 are individually addressable
and at least one wire 213 is bonded to each LED 10 and the other
end of each wire 213 is then bonded to electrical bond pad(s) 214.
These bond pads 214 are electrically isolated from each other. In
this drawing the LED(s) 10 are shown with an electrically active
heat pipe(s) 64 although electrically neutral heat pipe(s) may be
used in this embodiment as well as any other embodiment in this
patent application. The heat pipe 64 may be a common anode 11 and
each LED 10 would then be controlled by varying the resistance of a
resistor located between the die/wire bond and the power supply
cathode. If the heat pipe 64 is a common cathode 12, then the
current leading to each die 10 may be modulated directly (i.e.,
pulse width modulation and/or direct current modulation). This
figure depicts a total of nine LED die. Any number of die from one
to over one hundred by be employed. Also, any number of centered
wavelengths from one to more than one hundred may be employed. Most
preferably, wavelengths from the UV to the IR are used, with 400 nm
to 700 nm being the most preferable. This wavelength range may be
used in other embodiments in this application. The TIR reflector
10b is also shown. It is held in place by lens holder 215. The
circuit board and/or circuit board holder 216 is shown on which the
lens holder 215 is placed. The hemispherical concave surface 114 in
the reflector 10b is shown. It is preferably of a higher refractive
index than the material used in TIR reflector 10b so as to allow
more light to escape the chip, due to TIR in the chip. Also, light
rays may advantageously be bent at hemispherical concave surface
due to refraction caused by the differing refractive indices.
Aspherical, parabolic, elliptical, hyperbolic or defractive
surfaces may be substituted for the hemispherical surface. The
outside diameter of the heat pipe 64 is shown in the drawing by the
solid line drawn in a circle on the left. The nine LEDs 10 depicted
in the figure may be an assortment of red, blue, and green emitting
LEDs. It is understood that instead of three LEDs of each color,
only three LEDs total may be used (i.e., one green, one blue, and
one red). In the figure, rectangular (or other shape) strips of
each of the three primary colors could take up the space of three
of the nine squares shown in the LED 10. In other words, each of
the three primary colors may take up one-third of the available
(depicted) die space. This in some way might imply equal impedance
for a given die area for each color, although this might not be
true in all cases. Any organic and/or polymer LEDs could be
employed in any embodiment of the invention. Red inorganic LEDs may
preferably be used that are smaller in area than the blue or green
LEDs. Also, due to the human eye's ability to detect different
colors at differing apparent intensities (i.e., sensitivity) more
red than green, and more blue than green LED area may preferably be
employed.
[0128] FIG. 14 depicts the device of FIG. 13 in an array formed of
more than one device of FIG. 13. Actually, in FIG. 14 an array of
only three devices are shown for clarity. Between each heat pipe 64
is shown the circuit board 216. This circuit board may be of the
conventional epoxy laminate and/or it may be of solid conductive
material such as aluminum or copper with or without a
non-conductive polymer or ceramic layer (laminate). It may also be
wholly or partially ceramic, such as BeO, alumina, AlN, or other.
Circuit traces such as thin copper or gold or plated gold may
connect wire bonds 213 leading from the LED die (or dice). The
lenses 10a may touch each other and be circular at the contacting
final emitting surfaces or they may be molded into a square shape
at the final emitting surface and therefore have no "spacing"
between them. Also, a final lens element (or elements) may
preferably be employed after the final emitting surface for the
purpose of further beam shaping or environmental protection.
Additionally, circular holders may be employed around the lenses
10a.
[0129] FIG. 14a is similar to the cross-sectional view of arrayed
devices of the FIG. 14 with the addition of holders 98 as shown
around the individual lenses or reflectors 10a/b. Such holders
could be of any shape and size sufficient to support the individual
lenses 10a or reflectors 10b.
[0130] FIGS. 14b, 14c and 14d depict different "pixel" spacing and
geometric patterns. A "pixel" in this case is a heat pipe 64 with
the nine (or other number) shown LED(s) 10 on it. Each heat pipe
itself may be individually addressable as well as each individual
LED die on each heat pipe or some other combination. The ring 125
shown around each heat pipe may "nest" in a circuit board as shown
in the FIG. 14e. The heat pipes 64 are shown for clarity. The wires
213 are bonded to electrically isolated bond pads 214. When the
ring 125 is nested in a circuit board, a means for connecting
circuit board traces to the respective bond pads 214 on the ring
125 must be employed. This means may be accomplished by contacts
connected by traces and plated through vias. The LEDs 10 may then
be controlled by the voltage and currents that are applied to them
from the traces on the board (connected to a power source(s)),
through the wires 213 and then to the LEDs themselves. The wires
213 may be attached (as in all embodiments) to the die(s) 10 by a
wedge, ball, or other bond. Wedge bonding is preferable because the
wires stay more parallel to the board surface. Ball bonds can be
advantageous in that the wire sticks out vertically from the chip
and tends to attract the die encapsulating polymer in a manner that
pre-wets the chip and greatly reduces the formation of bubbles as
the lens or reflector is slowly lowered over the die(s).
[0131] FIG. 14e shows the blind female recesses in the circuit
board that accommodate the rings 125 from the devices shown in
FIGS. 14b, 14c and 14d. Contacts, vias, and traces are shown. The
preferably blind female recess(es) 217 in the board 216 are shown.
There are also preferably blind female recess(es) 217' depicted by
dashed lines in the board(s)that accommodate the heat pipe(s) 64.
There is a thin section of preferably board material that is of
high thermal conductivity between the two blind holes or recesses
217 and 217'. In the preferred embodiment, 217 and 217' are
substantially co-axial; however this need not be the case. There
may preferably exist a board laminate 218 preferably bonded on
board 216. In this embodiment of the invention as shown in FIG.
14e, the recesses 217 are actually through hole(s). Bond pads 214
that are aligned in FIG. 14b are shown with circuit traces on board
216. It is important to mention that through wires 213 under bond
pad(s) 214 in FIG. 14b are not shown in the figure but must be
present in order to make contact with bond pad(s) 214. The rings
125 from FIG. 14b may be square (or some other geometrical shape)
and would be accommodated by a like shaped recess 217'.
[0132] FIG. 14f shows a device somewhat similar to the one in FIG.
14b. It shows the heat pipe(s) 64 co-axial to a hole through board
216. Board 216 could be a "ring" similar to the ring 125 in FIG.
14b. The board 216 is shown with a thin wall surrounding the
multiple dies 10. In this drawing, the dies 10 are shown in a
"p"-side up embodiment. The active epitaxial layer is depicted on
the top edge of the die 10. May different LED or laser diode
structures and designs may be employed in all embodiments. In
particular, LEDs with an optically resonant structure may be used,
as well as LEDs or LDs that utilize "quantum dots". Hole 219 is
shown in the board 216 and wires 213 are shown leading from the
individual die 10 to their respective bond pads 214 and then to
respective circuit traces 220. The heat pipe 64 may or may not be
electrically active. If it is active, it may be the common cathode
and have an electrical connection to the wire 213 in the board 216.
Wire 213 may be conductive adhesive connecting the heat pipe 64 to
the circuit trace 220. Reflector 10b is shown. Light emission is
shown by the arrows pointed upward. The board 216 may be affixed to
a larger board with hardware or some passive locking arrangement to
that individual LED/heat pipe assemblies may be changed as they
wear out or technology warrants. Assemblies with multiple LEDs at
multiple centered wavelengths in or near the visible spectrum as
depicted in this figure and embodiment as well as others in this
patent application are ideal for automated stage light assemblies,
due to their compact, light weight, and high optical power, which
may preferably be computer controlled to change color, intensity,
hue, etc.
[0133] FIG. 14g shows heat pipe 64 inserted in a through the hole
219 of board 216. Reflector 10b is shown with LED dice 10. A two
part laminated board with traces between the layers is depicted as
top layer 216a and bottom layer 216b. Wires 213 in board 216 are
shown as wires making electrical continuity between the traces 220
sandwiched between layers 216a and 216b and the traces 220 on top
of 216. It should be noted that layers 216a and 216b, comprising
the circuit board 216, are optional in that the light can function
without a circuit board 216 and another means of connecting wires
from a power supply to the bond pads 214 can be employed in various
applications. Again, fins may preferably be attached to the heat
pipe 64 to employ convection or forced air cooling.
[0134] FIG. 15a shows four "pixels" (LED(s) on heat pipe devices)
that are arrayed on a circuit board. Only four devices (each
considered a "pixel") are shown in this drawing for purposes of
clarity. Actually, an array of pixels such as 48 by 64, or 48 by
32, or 24 by 16 for example may be employed. Examples of pixel
spacing preferably might be center to center spacing of 12 mm, 18
mm, 23 mm, 35 mm or 50 mm. Provisions for adjustment for
uniformity, dimming, brightness, hue, color space conversion and
gamma correction may be employed. A portion of the circuit board
216 is shown. On the tip of the heat pipe 64 nine individually
addressable LEDs 10 are shown. Each of these LEDs 10 have a wire
that connects to a bond pad 214 on the circuit board 216. Please
note that in this embodiment there is not a separate ring 125 as
shown in FIGS. 14b, 14c, and 14d. The wires 213 in this embodiment
lead from the separate LEDs on the heat pipe(s) to separate,
permanently affixed bond pads 214 on the circuit board 216. Only
one wire 213 in the entire drawing is shown, for clarity, as well
as only one abbreviated circuit trace 220. It should be obvious to
those skilled in the art to connect individual wires from
individual LEDs to individual bond pads, and then these bond pads
to appropriate circuit traces to light up the LEDs. Note how the
multiple heat pipes 64 form a "pin-fin" type heat sink. All of the
circumferential surface area of the heat pipes is used to conduct
heat to the ambient air that flows either by natural or forced air
convection between the pins (a.k.a. heat pipes) and the heat pipes
may have fins attached in any orientation to further increase
surface area. The space between the heat pipes allows air (or other
medium) to circulate and cool the heat pipes. The fins could
actually be all monolithic in a honeycomb-type design wherein the
bare heat pipes slide into holes in the all monolithic honeycomb
heat sink. This heat sink maybe made of any thermally conductive
material, and it may or may not be forced air cooled. If the fins
are not monolithic, but are joined to heat pipes, they may be at a
45.degree. angle (or so) to the heat pipe orientation, as well as
at a 45.degree. angle (or so) to the horizon to facilitate
naturally convective flow of air because heat will rise up through
the fins and draw cool air in behind. Also, the air will be forced
to impact the fins more directly than if they fins were mounted
perpendicular (vertical) to the horizon. As in all embodiments in
this application the heat pipes may have some other working fluid
than water or may have some other substance added to the water. In
an alternate embodiment, for example, alcohol (glycol, methanol,
etc.) may be added to protect from freezing. Also, other materials,
such as aluminum, could be used instead of, or in conjunction with
copper for the body (wall) or heat pipes. Lenses 10a are also
shown. These may be of the TIR variety or refractive, diffractive,
reflective, or a combination. When the LEDs 10 on one of the heat
pipe 64 are turned on in some combination, the pixel can be thought
of as "on" or "active". In general, each heat pipe's LEDs would be
some combination of individually addressable red, blue, and/or
green LEDs. As in all embodiments in the application "white" LEDs
may be employed.
[0135] FIG. 15b an array of heat pipes 64 that are inserted and
bonded in blind holes in a board 216. The blind holes 221 are more
clearly shown in FIG. 15c. The board 216 may be a printed circuit
board or simply a plate of metal (or other conductive or
non-conductive material) with circuit traces 220 leading to the
LEDs 10. A "group" of three LEDs are shown in this drawing for
clarity. One or more LEDs, at one or more centered wavelengths may
be used. This drawing also shows only three LED "groups" (the
fourth is hidden), four lenses 10a and three of four heat pipes 64.
It is understood that those few parts are only shown for clarity
and that they represent an array of perhaps hundreds that may be on
a single board 216 or multiple boards that are in themselves
arrayed edge to edge. The heat pipes 64 that are in the blind holes
may preferably be bonded into place with a high thermal
conductivity adhesive. The blind holes are deep enough that only a
thin layer of board material exists between the bottom of the hole
(where the tip of the heat pipe will rest) and the top of the board
216 where the LEDs 10 will be bonded immediately above the bottom
of the hole. In this way there will be minimal thermal resistance
from the LED flip-chip junction, through the thin board material,
through the adhesive, and into the heat pipe 64. The circuit trace
220 may be designed such that individual traces lead to LED chip
anode bond pads that "p" side down flip-chip LEDs 10 are soldered
to, and other traces lead to cathode wire bond pads that the wires
from the cathode side of the chips are bonded to. The circuit board
216 is preferably of aluminum for light weight and thermal
conductivity. It is preferably anodized to provide electrical
isolation form the chip bond pads, wire bond pads, and the traces
to and from them. Other thin-film processes may be used to deposit
the electrical isolation layer. The board 216 may be made from an
aluminum (or magnesium) epoxy or copper epoxy laminate. The LEDs 10
may also (but not necessarily) be individually addressed to
preferably have intensities at different time cycles more control
be made available to the end user.
[0136] FIG. 15c is a side view of just two (of many) heat pipes 64
of FIG. 15b clearly showing the blind holes 221 in the circuit
board 216. Only two lenses 10a are shown, for clarity and
orientation, as well as a few wire bonds 212 and a few LEDs 10.
[0137] FIG. 15d shows a typical forced-air cooled hand-held
embodiment of the present invention. It is understood that it may
also be fixed or mounted (not hand-held) and it might be
convectively cooled, i.e. no forced-air. A fan 66 is shown, with
heat pipes 64 and lenses/reflectors 10a/10b and emitting LED or
VCSEL light shown with arrows pointing downward. All the parts as
well as the LEDs 10 or VCSELs adjacent to the tips of the heat
pipes 64 are enclosed in a housing 222. Electrical power may be
supplied through an external cord from a power supply or from
batteries or from a combination of each or rechargeable batteries.
A gravity switch may preferably be employed wherein the switch
would only be electrically continuous when the LEDs 10 are pointed
substantially towards the ground. This would allow a gravity aided
feed in the heat pipe 64.
[0138] FIG. 15e depicts an embodiment of the present invention
wherein three separate LEDs 10 are disposed upon the end of a heat
pipe 64.
[0139] It is understood that the arrays discussed in this patent
application for display or other applications may or may not have a
heat pipe 64 immediately below the LEDs 10. The heat pipes 64
could, for example, be only used to transport heat and may be
randomly placed below the LEDs 10. The heat pipes 64 protrude from
a circuit board 216 in a direction that may be substantially
opposite to the direction of the emitting light. In this manner,
they act as heat transport pins to other broader surface area heat
sinks 68 or the outside diameter of the heat pipes 64 themselves
which may be used as the heat emission (or heat exchanging) surface
area without any additional bonded fins. Again, natural or forced
convection may be employed in any embodiment. Also a phase change
material (such as paraffin) may be used in any embodiment and may
surround the heat pipe(s). The paraffin may have a thermal
conduction enhancement material in it such as copper wool or
conductive particles. The circuit board 216 that the LEDs 10 are
affixed to may be affixed to another conductive (or non-conductive)
plate that, in turn, has heat pipes embedded in it.
[0140] FIG. 16 shows the Vertical Cavity Surface Emitting Laser
(VCSEL) embodiment of the instant invention. The drawing shows one
VCSEL 224 bonded to the top (tip) of a heat pipe 64. It is
understood that arrays of VCSELs 224 instead of just one may be
bonded to the ends of one or more heat pipes. It is further
understood that the VCSELs 224 (or for that matter, edge emitting
laser diodes) may be substituted for the LEDs 10 depicted in any
drawing or stated in any embodiment in this patent application. The
heat pipe 64 is shown within a sleeve 112. The heat pipe 64 and the
sleeve 112 may be electrically isolated. Also the sleeve 112 and/or
the heat pipe 64 may have a bend in them (0.degree. to 90.degree.
or more). This may also be the case in any other heat pipe/sleeve
combination shown in any embodiment in this patent application.
Anode 11 wire and cathode 12 are shown running from a sub-mount 14
to a low impedance "strip-line" type current/voltage carrying
device. This "strip-line" has two thin copper foil type tape anodes
11' and cathodes 12' running down the length of the heat pipe from
the VCSEL to the power supply or pulser. The copper foil tapes 11'
and 12' are insulated from each other as well as the heat pipe 64
and sleeve 112 (or other environment) preferably by Kapton type
tape 225. The VCSEL 224 may be of the high power type (over 1 W) CW
or much greater peak powers (over 1 KW). It may be pulsed with
short (such as ps pulses) or long (such as ms pulses). The
wavelength range may be from the UV to the IR. The laser light
emission with arrows pointed upward is shown emitting from a
partially reflecting output coupler mirror 226. The active region
and rear mirror are shown mounted to the conductive slug/submount
14. A transparent spacer assembly 227 is shown. Lenses 10a may be
desirably employed.
[0141] FIGS. 17 and 17a depict a separate heat sink 68 bonded to
the end of heat pipe 64. It is understood that this heat sink 68
could be electrolytically electro-formed onto the end of the heat
pipe 64. The electro-formed heat sink 68 could be made of copper.
In the preferred embodiment the heat sink 68 is bonded to the end
of the heat pipe 64 with high thermal conductivity glue. The LED 10
(or LEDs) is shown. The light emission from the LED 10 is shown as
arrows pointed upward. This embodiment may also be useful for
edge-emitting laser diodes. The dashed lines depict the blind hole
221 that is in the heat sink 68 to accommodate the heat pipe
64.
[0142] FIGS. 18a and 18b shows an embodiment wherein the LED 10 is
mounted to a flat side 64c or spot of the formerly cylindrical heat
pipe 64. It is not necessary that the heat pipe be formerly
cylindrical; it may be manufactured "flat". The light emission with
arrows pointed upward is shown. Arrays (more than one) of LEDs 10
may be bonded to the flattened portion of the heat sink 68 in any
orientation. The LEDs 10 may be soldered directly to the copper
heat pipe 64 with lead/tin or other solder 110. This embodiment is
preferable when a direct 90.degree. side emission in relation to
the heat pipe length axial direction is required. This is
especially useful for curing applications that require close
contact.
[0143] FIGS. 18c and 18d depict a laser diode 228 mounted directly
to a flattened portion 64c of a round heat pipe 64. The negative
anode wire 12 is shown along with symbol (-). The cathode in this
drawing is the heat pipe 64. It is marked with symbol (+). Light
emission with arrows pointed is shown. Also, solder 110 is shown.
An edge emitting, broad area laser diode bar may be employed.
Optional lenses may also preferably be employed. Lenses, such as
diffractive optical elements (DOE) may also be desirably used in
any embodiment to destroy the coherence of LDs. This makes them
safer and easier to market from a regulatory (FDA) standpoint. FIG.
18c is a front view of the device. FIG. 18d is a side view of the
device. Arrays of LDs, VCSELs, or LEDs, of individual chips or
combinations of all three (in any combination) may be preferably
used.
[0144] FIG. 18e shows a round heat pipe 64 that has been flattened
at one end, with LEDs 10 disposed upon the flattened portion of the
heat pipe 64. The center line 229 bisects the flattened portion of
through the center of the heat pipe 64. It should be noted that
while this figure depicts a round heat pipe 64 that has been
flattened only at one end, the present invention includes any round
heat pipe 64 that has been flattened for any portion of its length
so as to accommodate the reception of one or more LEDs 10.
Additionally, the heat pipe does not have to have ever been round,
as it may be manufactured flat. This is true for all embodiments in
this patent application.
[0145] It is noted that all embodiments in this application could
utilize microchip or thin disk laser technology. For example, the
active region of a microchip laser and/or gain media of a think
disk laser could be mounted on the tip of a heat pipe.
[0146] Additionally, in another embodiment of the present invention
there is provided packaged LED (or laser diode) device(s) which
provide superior thermal transfer which allows operating the LEDs
at a current substantially higher than manufacturer specifications
and in a package substantially smaller than the current
state-of-the-art. The packaged LED (or laser diode) device
preferably includes at least one LED, a sub-mount, a flex (or
rigid) circuit, and an optional TIR reflector. This packaged device
may be affixed to a heat pipe. The device may be used as a discrete
device, or with an array of similar devices for adhesive curing and
various other applications.
[0147] FIG. 19a depicts a high thermal conductivity material,
preferably a CVD Diamond, for use as a heat spreader/submount 230.
The diamond in this figure, preferably, is 100 microns thick and
has 50 micron diameter laser drilled through holes 219. These holes
219 facilitate the transfer of a thermally, as well as
electrically, conductive adhesive from top to bottom and/or bottom
to top of the substrate. The holes 219 may have walls that are
purposely sloped (not parallel) to allow for a bigger opening on
one side than the other to facilitate easier filling of conductive
adhesive. Other heat spreader/substrates, such as AlN or even
copper, may be used. Heat spreaders may also be metalized with a
pattern for one or more semiconductor die. The metalization may or
may not extend through holes that may exist in the substrate. They
may be metalized on one or both sides.
[0148] FIG. 19b depicts nine LED die 10 shoulder to shoulder on a
heat spreader/submount 230. These die may be approximately 300
microns.times.300 microns at the top (wire bond surface) and
approximately 200 microns.times.200 microns at the bottom "n"
contact surface. These dimensions allow the holes 219 shown in FIG.
19a to not substantially fall under any die surface. In other
words, the "streets" between the bottom of the die encompass the
holes 219. Conductive epoxy may be used to bond the dies 10 to the
heat spreader/substrate 230. Another means of affixing may be to
solder, provided that the substrate is first patterned and
metalized. The holes 219 allow electrical current to flow between
the top and bottom surface of the heat spreader/substrate 230. The
heat spreader 230 is preferably non-conductive although it could be
conductive if a metal such as copper or aluminum were employed. It
is understood that only one die 10 may be used or multiple dies 10
may be used. They may be in series, parallel, or other combination
and they may or may not be individually addressable. One or more
center wavelengths may be employed particularly if more than one
die is used, although multiple wavelengths can exist on one die. In
general, these wavelengths span the visible range from the
UV/visible edge to out near the visible/IR edge. If multiple
wavelengths are used, they may advantageously be employed to
selectively target photo-initiators in adhesives or coatings, and
may also be used to penetrate material to different depths. The
devices may be capable of being remotely adjusted for beam angle,
power, intensity, hue, color, etc. Usually, for most applications
with multiple wavelengths, i.e. dies having different centered
wavelengths, individual addressability is preferred. The devices in
this application have this inherent individually addressable
characteristic. The heat spreader 230 may preferably use only one
die 10. The holes 219 through it should not be directly under the
die(s) 10, but rather out from under it (them) in the periphery.
Holes 219 could be replaced by wire bond pads in an alternative
embodiment. Circuit traces 220 lead to the metalized bond pads(s)
214 in FIG. 19c. It should be understood that it is NOT necessary
to have holes 219 through the heat spreader 230. Circuit trace(s)
220 could simply lead to wire bond pad(s) 214 and a wire or wires
could be bonded to the pad(s) and terminate at another bond pad as
shown in FIG. 20 to facilitate completion of an electrical circuit.
This bond pad 214 could also take the place of through hole 219' in
FIG. 20, for example.
[0149] FIG. 20 shows layer 230'' which is a flexible or rigid
circuit material with a cut-out 231 through the center which allows
the LED die(s) 10 to come through from the layer 230''. It has wire
bond pads 214 and circuit traces 220 that extend out to the
preferred plated through holes 219. Each bond pad 214 may accept a
wire from an LED. One trace does not have a bond pad, but rather a
larger plated through hole 219'. This through hole 219' optionally
allows the same electrically conductive glue under the heat
spreader 230 to come through and contact the trace 220 connected to
it. This essentially allows the electrical polarity of the adhesive
under the heat spreader 230 that goes up through the holes 219 in
the heat spreader 230 and contacts the adhesive under the die(s)
10, to be the same polarity. In the preferred embodiment, this
polarity is "negative" (although it could be "positive") and allows
multiple die to share a common ground plane. This ground plane can
then have an electrically continuous path up through the through
hole 219' to a trace 220. Note that optional through hole 219' may
preferably act as the electrically continuous path that is on top
and in the same plane as the die(s). The preferably flex circuit
230'' in this figure is preferably of kapton or similar,
substantially non-conductive material with gold plated copper
traces that are patterned, etched, and (subsequently gold, or
other, plating). This circuit 230'' is available on a custom
designed basis from manufacturers. The cut-out 231 in the center
may be sized to just clear the die(s) 10 or it may be larger. It
may also facilitate conductive adhesive stenciling. It is bonded to
the preferably flex (or rigid) circuit material 230' as will be
shown in FIG. 20b through the use of a B-stageable adhesive layer.
Again, it is understood that the plated through hole 219' could be
negated by replacing it with a bond pad 214. A wire 213 could then
be bonded to this bond pad 214 and a bond pad or pads on the heat
spreader 230 that lead, for example, to a ground plane.
[0150] FIG. 20a depicts the "bottom view" of FIG. 20. The holes 219
and 219' are preferably plated through (i.e., the walls of the
holes, not including the center die cut-out, are electrically
conductive). This is often accomplished through the use of a
palladium emersion coating applied during the manufacture of the
flex (or rigid) circuit.
[0151] FIG. 20b shows the thicker circuit material 230' and shows
the top side. Note the cut-out 231' preferably by laser means
through the material preferably kapton or rigid FR4 Flex that
allows the heat spreader 230 of FIG. 19 to fit inside. The circuit
material 230' may also preferably be about the same thickness as
the heat spreader 230, i.e. approximately 75 to 150 microns. This
circuit material 231' with this side shown is bonded to the bottom
of layer 230'' of FIG. 20.
[0152] FIG. 20c shows the bottom side of the material 230' of FIG.
20b. Note that the round through holes 219 are preferably plated
through.
[0153] FIG. 20d shows the circuit material 230'' of FIGS. 20 and
20a bonded to the material 230' of FIGS. 20b and 20c.
[0154] FIG. 20e shows the bottom side of the two bonded materials
depicted in FIG. 20d. Note how the cut-out 231' is terminated by
the "membrane" like top circuit material 230''. This cut-out
accepts the dimensions of the heat sink 68. In fact, the heat sink
68 is glued into place by placing a drop of glue in the four
corners of this cut-out 231' and then the heat spreader material
230 is gently placed within the confines of the cut-out 231'. Note
that you can clearly see the optionally plated through holes 219
and 219'.
[0155] FIG. 21 shows the previously described circuit material
230'' with nine LED dies 10 bonded to it with an electrically and
thermally conductive means. The nine dies are for example only. One
or more dies may be used. In this example, they are marked "p" side
up, although "p" side down with individually addressable bond pads
214 may be employed. Each die 10 (or packaged die) may be
controlled by a computer controlled resistive element between the
die cathode lead 12 and a power supply, useful when the LED 10 is
mounted "p" side down on a heat sink 68 that may have an
electrically conductive common anode. If the "p" side is not on a
common anode (each LED "p" side is electrically isolated from the
rest) the current may be directly modulated between the power
supply and the "p" contact. Pulse-width modulation may preferably
be employed. If the chips are mounted "p" side up, they could share
a common cathode and desirably be modulated individually by a
computer controlled current modulator between the "p" contact and
the power supply. The traces to the bond pads 214 in FIG. 21 could
be etched and/or buried in a silicon or other semiconductor layer
that could be on top of a high thermal conductivity material such
as diamond or traces 220 could be copper on top of flex or rigid
circuit 230''. Wires 213 are shown from the top of the LEDs to bond
pads 214. The LEDs 10 may preferably be placed in the proper
position using automated pick and place equipment with machine
vision capabilities.
[0156] FIG. 22 shows a ring 232 that sits on top of the circuit
material 230'' of FIG. 20. It is a strengthening member first, but
it can also be used as a current equalizing member between all the
traces 220 if it has some electrical conductivity. It may also
serve as a pin guiding member. This conductivity may result from it
being a metal or coated with a metal. Furthermore, the conductivity
between it and the traces 220 and/or the plated through holes 219
may be established through the use of an electrically conductive
adhesive or solder. The through holes 233 of the ring 232 are
aligned over the through holes 219 of the circuit material 230''
and adhesive may be injected in them and/or they may contain pins
that come up through the plated holes 219 that facilitate
electrical interconnections which will be explained later in
detail. The ring 232 could also preferably be non-conductive.
[0157] FIG. 22a shows the ring 232 of FIG. 22 affixed to the top of
circuit 230. Circuit traces 220 and wire bond pads 212 are shown.
It is understood that circuit traces 220 and pads 212 could be a
monolithic circular annular ring around the outer periphery of
circuit 230'' if all of the LEDs 10 (or a single LED) were
electrically driven together in parallel and were not individually
addressable. The ring 232 could be connected to an outer sleeve by
conductive adhesive to facilitate electrical connection. The
adhesive could be applied to both parts through a hole in the
sleeve.
[0158] FIG. 22b depicts the assembly of FIG. 22a with a TIR
lens/reflector 10a/b over the LED(s) 10. It has a hemispherical
cavity in the bottom of it (not shown) that is filled with a
preferably heat curable index matching compound. This compound (or
gel) allows greater light extraction from the LED die due to its
index matching properties. It may be placed on the hemisphere and
allowed to partially cure. This partial cure increases its
viscosity. The LED(s) may be lowered into the gel in a chamber that
is of a pressure lower than ambient. It may also be allowed to
fully or partially cure at this sub-ambient pressure. This
procedure can lower the risk of a bubble formation. It is important
that TIR lens/reflector 10a/b be lowered over the LEDs at a rate of
around 1 micron/second or less. Again, the hemispherical cavity
does not have to have a spherical shape. Lens/reflector 10a/b could
have metalized walls. It also could preferably have an annular
"step" at its point of smallest circumference to act as an index
matching compound reservoir.
[0159] FIG. 22c shows a bottom view of the assembly of FIG. 22b,
but for purposes of explanation the heat spreader 230 with the
attached LED(s) 10 is shown removed from the assembly. Shown herein
is the circuit layer 230'' and the reflector 10a/b is shown for
purposes of orientation.
[0160] FIG. 22d shows the assembly of FIG. 22c with the heat
spreader 230 shown. Uncured conductive adhesive 234 is shown
smeared on the bottom of heat spreader 230. It is applied in such a
fashion as to make sure that adhesive goes up the through hole 219'
to the LED die 10 (not shown) and also, if desired or applicable,
over to hole 219' and up it. Again, this is the case if one is
trying to facilitate an electrically continuous path from the
bottom of the assembly or heat spreader 230 (or heat sink 68, or
slug 14) to the top surface of the heat spreader 230 in the same
plane as the LEDs. It is noted that adhesive 234 can be spread on
top of heat pipe 64 prior to the assembly of FIG. 22d affixed on
the heat pipe 64. It is understood that the assembly of FIG. 22c
does not need to be mounted on a heat pipe 64 (not shown). It is
quite acceptable to mount this assembly on a circuit board and use
the heat spreader 230 to spread heat and lower thermal resistance.
If not mounted on a heat pipe 64, the assembly may become a SMT
(surface mount technology) device. When mounted to a circuit board,
traces on the board could lead to plated through hole 219' (which
could be plated solidly through) and could serve the purpose of
either an anodic or cathodic contact. In this description the heat
spreader 230 could have holes in it providing a polar contact. It
is preferable that solder 110 be used in this particular embodiment
as adhesive can wander and short out the device. In this, case
adhesive blob 234 would not be present. The solder 110 may be
applied to the proper places on the assembly or to proper pad(s)
214 on a circuit board 216 not shown.
[0161] FIG. 22e depicts the assembly of FIG. 22d with a
strengthening ring 236 and a heat pipe 64 shown. The heat pipe 64
shown is a flattened (although it can be round) and, for example
only, has an oval dimension of 2 mm.times.3.7 mm.times.200 mm in
length. The strengthening ring 236 may also be thermally conductive
so as to spread some heat from the LEDs 10 to the side walls of the
heat pipe 64. This may lessen the chance of "dry-out" as the heat
is spread over a larger surface of the heat pipe 64. The assembly
of FIG. 22d is affixed to the plane dictated by the top (tip or
end) of the heat pipe 64 and the ring 236 that surrounds it. A
thermally and electrically conductive glue may be used for the
affixation. The finished assembly may be placed in a female
receptacle in a circuit board (not shown) wherein conductive
"bumps" or pins could make contact with the plated through holes
219. These "bumps" could be attached to circuit traces 220 in or on
the board 216, that could then turn on and off the current to the
desired plated through holes which would then result in selected
(or all) LEDs turning on or off (or some level in between) at the
selected level(s), intervals, and intensities. The "bumps" may be
placed on the hole(s) 219 or on a circuit board 230 (not shown) or
both as will be shown and described in greater detail in FIG. 24
and FIG. 25 below.
[0162] FIG. 22f depicts the bottom view of an alternative
electrical interconnection scheme to that described in FIG. 22e.
This scheme uses conductive pins 237, similar to nano connectors,
to complete the conduction path from the LED, through the wire,
through the trace, through the plated through hole, into the
conductive pin(s) 237, and the pin(s) 237 into a mating female
sleeve or plated through hole located in a circuit board that has
appropriate circuit traces to the female sleeves and to a
controller and power supply. The assembly in this drawing has a
different style strengthening ring 236' than the strengthening ring
236' of FIG. 22e. Heat pipe 64 is shown, but as in all drawings,
has only a portion of its length depicted for clarity. The pin(s)
237 could alternatively be placed in a circuit board and female
receptacles or plated through holes in ring 236' and/or hole(s) 219
of FIG. 20.
[0163] Note how the pins(s) 237 protrude from both the top and
bottom of ring 236. The top portion of the pins can go into the
holes in ring 232 of FIG. 22 and the bottom portion slide into
appropriate female receptacles in a circuit board as will be shown
and described in detail in FIG. 23. The circuit board may have an
array of complete LED assemblies whose LEDs are individually
addressable. These arrays may be used for applications such as
curing glues, inks, or coatings. The arrays used for curing or
other photo initiated chemical reactions may have multiple
wavelengths strategically turned on at proper times at strategic
wavelengths and intensities. The arrays could be activated and
controlled remotely using wi-fi or blue tooth or other wireless
means and protocols. This would greatly reduce the demands of
routing traces to all devices on a large and densely packed circuit
board.
[0164] FIG. 22g shows a complete assembly with the assembly of FIG.
22d affixed to the assembly of Drawing 22f. The pin(s) 237 may be
glued into the holes of ring 232 (not shown) as well as the
preferably plated through holes 219 (not shown). One, or possibly
more, pins may be used as a ground (cathode). If a pin or pins are
used they may be glued with electrically conductive adhesive 234 or
solder 110 into hole(s) 219 that has a trace leading to hole(s)
219' as shown in FIG. 20. This may facilitate the negative
(cathode) connection of the assembly. There are preferably many
different embodiments possible for facilitating a ground
connection. The ground connection may take place on the same plane
as the bottom of the LED(s), on the bottom of the heat spreader, a
combination of each, or some other possibility that one skilled in
the art could conceive.
[0165] FIG. 22h depicts one aspect of the present invention, a
total internal reflecting (TIR) lens 10a that includes a concavity
99 at the end of the lens 10a within which an LED 10 is to be
disposed. Note that the concavity 99 could be filled with an
index-matching gel to surround and encapsulate the LEDs disposed
within the cavity of the lens 10a. The TIR reflector 10a depicted
in this figure may be molded of, for example, Zeonex E48R and it
may be produced by a micron-tolerance-capable injection-molding
machine. The index-matching gel that surrounds and encapsulates the
LEDs 10 has a refractive index between the refractive index of the
LED substrate and/or epitaxial layers and that of air, and
preferably has a refractive index greater than 1.59.
[0166] FIG. 23a shows an array of heat pipes 64 inserted into
circuit board 218. Preferably, the length of the heat pipes 64 are
200 mm and the dimensions of the board 218 are 25 mm.times.100 mm
stacked. These dimensions would allow two 100 mm.times.100 mm
stacked fans 66 to blow air though the array of heat pipes 64 in a
dimensionally compact and space conserving manner. Note that by
using oval (flattened) heat pipes, air flow between the heat pipes
is torturous which results in turbulence, which increases heat
transfer. Also note that the oval shape(s) in the circuit board(s)
218 may "key" the entrance of the heat pipes such that the assembly
of FIG. 22g could be affixed to this board by the friction of its
pins 237 matching up with the array of small holes 238 in this
figure. The small holes 238 contain the female receptacles (or
sockets) that are themselves connected to circuit traces that
ultimately control the LEDs. It is to be noted that instead of pins
and sockets, "bumps" could take the place of either-the pins, or
sockets or both.
[0167] FIG. 23b depicts an alternate arrangement for the heat pipe
64 ovals of FIG. 23a. It is an even more tortuous path for more
turbulence between the preferably oval heat pipes. Round or other
shaped heat pipes 64 may be used. Note the sockets 239 for pins 237
and the traces to the sockets.
[0168] FIG. 24 shows the LED (or laser diode or VCSEL array)
assemblies of FIG. 22g being inserted into the circuit board
assembly 216 of FIG. 23a. Note the oval shaped holes 238 that "key"
and/or accept the oval heat pipes 64. The optional blind circular
holes 221 in the top portion of the circuit board 216 accept the
strengthening rings of the assemblies of FIG. 22g. Also, note the
circuit traces 220 (only a few are shown for clarity) on circuit
board 216 beneath the top board layer that contains the blind
circular holes 221. Also the holes 238 contain the female
receptacles for pins 237. The receptacles in 238 are connected to
the traces 220 and the traces lead to a controller and/or power
supply. Each LED 10 assembly on each heat pipe 64 of FIG. 24 is
thought of as a "pixel" that is individually addressable. Each
"pixel" may also have nine (for example only) individually
addressable LEDs. The waste energy from the LEDs 10 is carried
straight back through the heat pipes 64 and distributed across the
circumferential surface area of the heat pipes 64 which is somewhat
analogous to a the operation of a "pin" in a "pin-fin" heat sink.
In the most preferable embodiment, a red, a green, and a blue LED
10 are mounted on or in the region immediately adjacent to the tip
of the heat pipe 64 and each are electrically individually
addressable. It is understood that multiple red, green, or blue
LEDs may be mounted together and/or in any combination and have
different centered wavelengths. The traces 220 are also shown in
FIG. 23b and the female holes 238 are also depicted and described
in FIGS. 23a and 23b as well as this FIG. 24. Optionally a second
strengthening board 240 on top of the board 216 has circular,
rather than oval holes. These circular holes accommodate the round
strengthening ring(s) 232.
[0169] FIG. 25 shows the assembly of FIG. 22b and FIG. 22d within
an outer sleeve 112. The sleeve 112 has a hole through it by which
a conductive adhesive 234 or solder 110 may be injected. This
adhesive can then serve as an electrical conduction path between
the conductive ring 232 of FIG. 22 and the conductive sleeve 112.
This sleeve may be made from aluminum and it may be anodized or
electrophoretically coated which serves as an electrically
isolating coating. However, the through hole 112 is not coated,
thereby the adhesive can contact an electrically conducting
surface. The sleeve 112 and the heat pipe 64 are electrically
insulated from each other by way of example in this FIG. 25. For
purposed of drawing orientation, the reflector/lens 10a/10b is
shown with the arrows depicting light emitting from the LED or LD
device. In this figure, the heat pipe 64 is the "anode" and the
current goes through the LED and through the wire 213 and then into
the conductive ring 232 and then into the conductive adhesive 234
and finally into the conductive sleeve 112. The heat pipe 64 is
connected to the "positive" battery or power supply terminal and
the sleeve 112 is connected to the "negative" battery or power
supply terminal, the polarity may be reversed depending on polarity
of LED die/dice.
[0170] In an additional embodiment, there is shown LED packages
according to the present invention manufactured and assembled using
Printed Circuit board (PCB) techniques described herein. Referring
to FIG. 26a, there is shown a first layer 260 made preferably of
polyimide and have a preferred thickness of around 0.001'' to
0.002''. This layer 260 may have photo imaged and etched metal,
preferably copper, circuit traces 220. The first layer 260 may be
in sheet form of approximate dimensions 12'' to 18'' and many, if
not all succeeding layers may have the same approximate dimensions.
This first layer 260 is bonded to the second layer 261 which is
also preferably polyimide and is approximately 0.004'' thick. This
layer 261 may have a square hole laser cut in it to accommodate the
eventual insertion of a heat spreader 230. This heat spreader 230
is preferably of a highly heat conductive material such as CVD
diamond as mentioned before. LEDs or LDs 10 may be bonded to the
heat spreader 230 and have wire bonds leading to traces 220.
Stiffeners 262 and 262' may be bonded to layers. These stiffeners
are also preferably of a polyimide material which is available in
thicknesses around 0.040''. These stiffeners could also be
injection molded plastic and assembled individually rather than in
board format. The stiffeners may be assembled individually if the
layers 260 and 261 are manufactured with a real-to-real or
roll-to-roll flex circuit manufacturing process. The lens and/or
reflector 10a/b may be bonded on or over the LEDs or LDs 10 while
all layers 260, 261, 262 and 262' are in "panel" format, i.e.,
components are not yet singulated from the "panel" or "board". All
the layers may be registered (aligned) to one another as they are
bonded. The reflectors or lenses may be assembled in trays to match
the center to center spacing of the LEDs 10 or LD devices on the
panels (boards). The tray of reflectors or lenses 10a/b may then be
lowered into the panel of LED/LD devices. In such a fashion the
reflectors or lenses 10a/b may be assembled over or on the LED/LD
devices in an array format to affect high volume manufacture. Pins
237 may also be added while in panel format. Solder bumping, stud
bumping, etc., may also be accomplished while in panel format.
After all layers and components have been bonded and/or assembled,
the individual LED or LD devices may be laser singulated from the
panel. A UV laser system may be employed for this task. The LED or
LD devices (or "packages") are singulated by the laser cutting
through all of the layers and thereby separating the devices from
the panel of laminated layers. Polyimide is a preferred layer
material because it is laser cut very cleanly and efficiently.
Automated pick and place equipment, as well as adhesive dispense
equipment, may be employed during all phases of assembly. The
lenses/reflectors 10a/b may be arrayed on trays, on the UV tape,
electro-static or vacuum chuck whether assembled in array/panel
format or assembled individually using automated pick and place
equipment.
[0171] FIG. 26b shows an array of LED packages manufactured
according to the present invention after the packages have been
assembled and then singulated by laser-cutting.
[0172] FIG. 26c is an exploded view of one post-singulation LED
package manufactured according to the present invention.
[0173] FIG. 27 shows an individual device similar to devices shown
in FIGS. 26a, 26b and 26c, except that the preferably polyimide
circuit layer 260 is bonded not to another polyimide layer 261
(that has a cut out in it for heat spreader 230 as shown in FIGS.
26a and 26c), but is instead bonded to a monolithic, highly thermal
conductive heat spreader without any surrounding polyimide layer
261. Layer 263 can be pre-laser cut diamond and assembled using
pick and place equipment while the LED devices still exist in panel
format i.e., stiffener layer 262' and polyimide circuit layer 260
have not been laser separated from the panel, or layer 263 may be a
large wafer, (preferably 1 foot diameter,) and this wafer may be
bonded to the polyimide circuit layer 260' which is also bonded to
stiffener layer 262'. Both layers 260 and 262' may also preferably
be 1 foot diameter, similar to 1 foot diamond layers 263. Two one
foot diamond layers 263 may preferably be bonded on to polyimide
layer 260 or layer 262', as layer 260 is optional if circuit traces
220 are deposited directly on 263.
[0174] FIG. 27a shows a bottom-side view of the LED package of FIG.
27 wherein the no cut-out bottom layer 263 is a highly thermally
conductive material such as diamond. Holes through this layer 263
may be laser drilled and plated through after a first conductive
metal "seed" layer is first deposited by vapor or liquid means.
[0175] FIG. 28a shows a side view of the LED packaged device of
FIG. 27. The TIR reflector 10a/b' has its elliptical or parabolic
side wall portion significantly shortened in overall length as
opposed to that of reflector 10a/b in FIG. 26a. This shortening in
length increases the output divergence of the light as opposed to a
longer side wall reflector. Also, this figure depicts a package
that is more "hermetic" in its environmental sealing from
contaminants. This is accomplished by the top surface of reflector
10a/b' having a larger flat plate-like integral "hat" 264. This
"hat" 264 sits down in a counter bore in stiffening ring 265. Note
the LEDs 10 for the purpose of drawing orientation. Epoxy or solder
or other adhesive is used to seal "hat" 264 to stiffening ring 265.
Element 266 is also a polyimide circuit layer. The heat spreader is
denoted by 230.
[0176] FIG. 28b depicts an LED package similar to that in FIG. 28a,
except the polyimide or other non-conductive material 266 is of
greater thickness and the concave hemispherical portion of
reflector 10a/10b' is of less curvature. The circuit layer 266 is
nearly as thick as the LEDs 10 are. The reason for this is that the
LEDs 10 shown have the epitaxial layer 267 on top of the LED 10 as
opposed to a "flip-chip" structure wherein the epi layers are on
the bottom of the chip, where it is bonded to a submount or heat
spreader 230. Since the LED structure is on top, the circuit layer
266 may be thicker without absorbing much emitted light out of the
sides of the chip. Primarily the advantage is that the excess index
matching gel 268 that surrounds the chip(s) is less likely to flow
on the sides of the TIR reflector 10a'/b' and destroy the TIR
properties i.e., couple out light through the sides because the gel
268 has a cavity to flow into that is not in such close proximity
to the reflector wall. The cavity is defined by the thick (high)
side walls of the square cavity that is laser cut-out or punched in
circuit layer 266. The heat spreader 230 may be thicker than layer
261. As such it would "stick out" a little and may give clearance
for solder bumps used as connection devices near the outer diameter
"periphery" of the device. This clearance helps to alleviate some
stress in the solder bumps if the package is not so firmly pulled
down onto the circuit board. The layer 267 may be of essentially
the same thickness as layer 262. Lastly layer 267 may be thinner
than layer 262 which would allow extra room for the bonding means
of layer 267 to the heat pipe 64 or circuit board 216. This extra
room can alleviate stress in the bond layer.
[0177] FIG. 29 shows a bottom-side view of an LED packaged device
of FIG. 27 wherein the hypotenuse of the heat spreader 230 is
almost as long as the cord of the diameter of the captive polymer
layer 269. This greater surface area of the heat spreader 230
allows a greater area to conduct heat through in a small diameter
package, which by nature has a smaller diameter polymer layer/ring
269. If nine individually addressable LEDs are employed, there is
an inherent need for nine conductors plus a ground. These nine
conductors may be plated through holes 219 through the heat
spreader 230. Importantly, three such conductors are located
symmetrically on each of the four sides of the heat spreader 230.
The hole(s) 219 are connected to circuit traces found on top of the
heat spreader 230. These traces are then wire bonded to the LEDs or
LDs 10. These hole(s) 219 may be connected to a circuit board that
controls the packaged device via solder bumps on the device and/or
board, conductive (anisotropic or isotropic) adhesive bumps on the
device and/or board, stud bumps on the device and/or board,
pins--preferably compliant on the device and/or board, solder paste
on the device and/or board, solder pads or preforms on the device
and/or board, or anisotropic conductive film. Conductive adhesive
or solder paste may be injected in holes 219. This list is by no
means meant to be exhaustive or all inclusive.
[0178] FIG. 30a depicts a flattened flexible heat pipe 64 with
LED's or LD's 10 bonded to it. This heat pipe could be less than 1
mm or also be thicker than 1 mm. One or more LEDs or LDs 10 may
first be mounted onto a submount, individually or collectively
i.e., monolithic submount. The heat pipe 64 may conduct electricity
and, as such, be either an anode or a cathode. Arrows from LEDs 10
depict light emission. The LEDs 10 may be in series, or in parallel
or be individually addressable. This flexible device may be
encapsulated in a transparent polymer. It may be used as a strap
like device to wrap around a human or animal body part for light
therapy. This same purpose may result from the use of device in
FIG. 30b.
[0179] FIG. 30b depicts the heat pipe of FIG. 30a. This heat pipe
64 has one or more organic Light Emitting Diode(s) (OLED) 10'
bonded to it. This allows for a very thin structure and the heat
pipe 64 is preferably longer than OLED 10' and transports the waste
heat away from the OLED 10' to a heat sink 68 or dissipates the
heat energy to ambient air.
[0180] FIG. 30c shows the heat pipe 64 bent around a finned heat
sink 68. This heat sink may be made up of one or more extruded,
molded, or machined heat sink(s) 68. The finned heat sinks 68 allow
for more surface area for the heat from the LED device(s) 10 to be
dissipated, through either natural or forced air convection. The
device in the drawing may be used for applications requiring a
large emitting area with or without corresponding high or greater
than 10 W output power. High output power may be used in various
such applications utilizing LED 10. treatment. An OLED 10' may be
used where LED 10 is shown.
[0181] Referring to FIG. 31a, there is shown an array of LEDs 10 on
a diamond submount 301 which is then bonded to a heat pipe 64. The
diamond submount 301 is non-conductive, although it could be doped
with boron to make it electrically conductive. The top surface 301a
of the diamond 301 is metalized. This metalized layer serves as the
"p" contact 303 metalization and is the common "p" contact for all
of the LEDs (1-N in number) 10. "n" wire 302 and "p" wire 303 are
shown only one for clarity. The LEDs 10 in this embodiment are
preferably "metal-backed" LEDs, but various other LEDs may be used.
This depiction is ideal for use in various applications preferably
without a lense. A transparent flat (planar) window is
preferred.
[0182] FIG. 31b depicts an array of four (although 1-N may be used)
LEDs 10. In this embodiment, the "n" 302 and "p" 303 contacts are
on the same side of the chip and the chips are connected in
electrical series. This array may be placed on a heat pipe 64
similar to FIG. 31a.
[0183] All the devices in this patent application can be used with
blue (0.465 mm) light to activate photo initiators or other
chromophors or sensitizers in curing adhesives or composites or
other substances, as well as used in devices that may or may not
contain light sensitizers, chromophors, or photoinitiators. The
devices of the present invention may be used in conjunction with a
variety of different compositions which are curable using
electromagnetic radiation, as described herein. For example,
compositions which harden or crosslink to form coatings, sealants,
adhesives or articles of manufacture may be subjected to radiation
emitted from the inventive devices to effectuate hardening or
polymerizing. A wide variety of materials and compositions may be
employed. For example, compositions including polyolefins,
acrylates, epoxies, urethanes, polyesters, acrylimides,
cyanoacrylates, silicones, polyamides, polyimides, polyvinyl
compounds, latex compounds, among others, may be cured using
radiation emitted from the present inventive device. These
compounds rely on a variety of different chemical mechanisms to
harden or polymerize. Generally, the ability to polymerize using
light radiation, includes the use of compounds or complexes which
initiate or induce or otherwise accelerate the polymerization
process. Frequently, one or more of these additional compounds,
usually referred to as photoinitiators, photosensitizers or
chromophors, are added to the polymerizable material to enhance
both the speed and/or thoroughness of the cure.
[0184] Examples of useful radiation curable compositions
particularly include anaerobic compositions, such as those
described in U.S. Pat. Nos. 4,415,604; 4,424,252; 4,451,523;
4,533,446; 4,668,713 and 6,150,479, all to Loctite Corporation, the
subject matter of which are entirely incorporated herein by
reference.
[0185] Additional information with respect to anaerobic
compositions is provided in Structural Adhesives, Chemistry and
Technology, Chapter 5, Ed. By S. R. Hartshorn, 1986 Plenum Press,
N.Y., the subject matter of which is incorporated herein by
reference.
[0186] Particularly useful photoinitiators include ultraviolet
light photoinitiators, which are capable of curing mono and
polyolefinic monomers. These include benzophenone and substituted
benzophenones, acetophenone and substituted acetophenones, benzoin
and its alkyl esters and xanthone and substituted xanthones, among
others. Specific photoinitiators include diethoxy-acetophenone,
benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether,
diethoxyxanthone, chloro-thio-xanthone, azo-bisisobutyronitrile,
N-methyl diethanol-amine-benzophenone and mixtures thereof.
[0187] Other examples of initiators include visible light
initiators such as camphoroquinone peroxyester initiators and
9-fluorene carboxylic acid peroxyesters.
[0188] The preferred embodiments described herein are intended in
an illustrative rather than a limiting sense. The true scope of the
invention is set forth in the claims appended hereto.
* * * * *