U.S. patent application number 15/182396 was filed with the patent office on 2016-12-08 for led flashlight with improved heatsink.
This patent application is currently assigned to Mag Instrument, Inc.. The applicant listed for this patent is Mag Instrument, Inc.. Invention is credited to Anthony Maglica.
Application Number | 20160356480 15/182396 |
Document ID | / |
Family ID | 56128968 |
Filed Date | 2016-12-08 |
United States Patent
Application |
20160356480 |
Kind Code |
A1 |
Maglica; Anthony |
December 8, 2016 |
LED Flashlight with Improved Heatsink
Abstract
One electrical lead from an LED package is soldered to an inner
electrically conductive member positioned and electrically isolated
from an outer electrically conductive member by electrically
insulating material while a second electrical lead and a neutral
lead from the LED are soldered to the outer electrically conductive
member so that heat is transferred from an LED die within the LED
package to the outer electrically conductive member and then to a
thermally conductive outer casing with a thermal path that
minimizes thermal resistance.
Inventors: |
Maglica; Anthony; (Ontario,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mag Instrument, Inc. |
Ontario |
CA |
US |
|
|
Assignee: |
Mag Instrument, Inc.
Ontario
CA
|
Family ID: |
56128968 |
Appl. No.: |
15/182396 |
Filed: |
June 14, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15148505 |
May 6, 2016 |
9453625 |
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15182396 |
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14971971 |
Dec 16, 2015 |
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15148505 |
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62095733 |
Dec 22, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F21L 4/085 20130101;
F21V 17/101 20130101; H01M 10/0481 20130101; H01M 10/613 20150401;
H01M 10/655 20150401; F21V 19/005 20130101; F21L 4/027 20130101;
F21V 29/503 20150115; F21V 29/89 20150115; F21V 23/0428 20130101;
H01M 2/204 20130101; H01L 33/62 20130101; H01M 2/1055 20130101;
F21V 17/12 20130101; F21Y 2115/10 20160801; F21V 3/00 20130101;
H01M 10/623 20150401; H01L 33/642 20130101; H01L 2224/48091
20130101; Y02E 60/10 20130101; F21V 29/70 20150115; F21V 29/713
20150115; F21V 15/04 20130101; F21V 23/06 20130101; H01L 33/483
20130101; H01M 2220/30 20130101; F21V 7/00 20130101; F21L 4/005
20130101; H01M 10/643 20150401; H01L 2224/48091 20130101; H01L
2924/00014 20130101 |
International
Class: |
F21V 29/70 20060101
F21V029/70; H01L 33/62 20060101 H01L033/62; F21L 4/00 20060101
F21L004/00; H01L 33/64 20060101 H01L033/64 |
Claims
1. A lighting apparatus, comprising: an outer casing that is
thermally conductive; a light emitting diode ("LED") package
contained within the outer casing, said LED package comprising: a
substrate; an LED die held by the substrate, said LED die
configured to emit light outwardly from a front surface of the LED
package; a first electrically conductive pad; a second electrically
conductive pad; and a thermal pad configured for removing heat from
the LED die to outside of the LED package; wherein the first and
second electrically conductive pads are configured to provide power
to cause the LED die to emit light; wherein the first and second
electrically conductive pads and the thermal pad are located on a
rear surface of the LED package opposite from the LED die; and a
heatsink assembly held within the outer casing, said heatsink
assembly comprising: an outer electrically conductive member that
is thermally conductive and which is mechanically connected to the
outer casing; a core of an electrically insulating material which
is held within a cavity formed in the outer electrically conductive
member; and an inner electrically conductive member which is
positioned and electrically isolated from the outer electrically
conductive member by the core; wherein the first electrically
conductive pad and the thermal pad are thermally and electrically
bonded to a first top surface of the outer electrically conductive
member without use of a printed circuit board and the second
electrically conductive pad is electrically bonded to a second top
surface of the inner electrically conductive member.
2. The lighting apparatus of claim 1, wherein the first
electrically conductive pad and the thermal pad are soldered to the
first top surface and the second electrically conductive pad member
is soldered to the second top surface.
3. The lighting apparatus of claim 1, wherein the core and the
inner electrically conductive member are comprised of a single
molded assembly.
4. The lighting apparatus of claim 1, wherein the core is
configured to form a passageway between the core and the outer
electrically conductive member when the core is inserted into the
cavity.
5. The lighting apparatus of claim 4, further comprising an epoxy
held within the passageway.
6. The lighting apparatus of claim 5, further comprising a
mechanical means for holding the core within the cavity.
7. The lighting apparatus of claim 5, further comprising a printed
circuit board ("PCB") held within the core in a vertical
orientation with respect to the first top surface.
8. The lighting apparatus of claim 1, wherein the lighting
apparatus is comprised of a flashlight and the outer casing is
comprised of a flashlight barrel.
9. A method for creating a flashlight mode with increased lumens or
with increased on-time, comprising: inserting a core which holds an
inner electrically conductive member into a cavity formed in an
outer electrically conductive member so that a second top surface
of the inner electrically conductive member is positioned within an
opening in a first top surface of the outer electrically conductive
member and the inner and outer electrically conductive members are
electrically isolated from one another; soldering both a first
electrically conductive pad and a thermal pad of a light emitting
diode ("LED") package to the first top surface without use of a
printed circuit board as well as soldering a second electrically
conductive pad of the LED package to the second top surface to form
a heatsink assembly, wherein said LED package is comprised of the
first electrically conductive pad, the second electrically
conductive pad and the thermal pad, wherein the first and second
electrically conductive pads are configured to provide power to
cause a die within the LED package to emit light outwardly from a
front surface of the LED package, wherein the thermal pad is
configured for removing heat from the LED package, and wherein the
first and second electrically conductive pads and the thermal pad
are located on a rear surface of the LED package opposite from the
die; and inserting the heat sink assembly into a flashlight barrel
so that the heat sink assembly is held by mechanical contact with
the barrel and a thermal path is created between the flashlight
barrel and the first electrically conductive pad and the thermal
pad of the LED package which is only interrupted by a first thermal
junction between the flashlight barrel and the outer electrically
conductive member and a second thermal junction between the outer
electrically conductive member and the first electrically
conductive pad and the thermal pad of said each LED package;
wherein providing power to the first and the second electrically
conductive pads of the LED package cause the die within the LED
package to emit light.
10. The method of claim 9, further comprising the step of putting
epoxy into a passageway formed between the core and the outer
electrically conductive member after the core is inserted into the
cavity.
11. The method of claim 10, wherein the epoxy creates a mechanical
means for holding the core within the cavity.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part application of
U.S. Ser. No. 15/148,505, filed May 6, 2016, and is also a
continuation-in-part application of U.S. Ser. No. 14/971,971, filed
Dec. 16, 2015, which is a non-provisional application which claims
priority from U.S. Ser. No. 62/095,733, filed Dec. 22, 2014, the
disclosures of all of which are specifically incorporated by
reference herein in their entireties.
FIELD OF THE INVENTION
[0002] This application is in the field of flashlights that use
surface mount light emitting diodes (LEDs) as light sources.
BACKGROUND OF THE INVENTION
[0003] It is well known that LEDs give off heat during operation
and that light output from an LED decreases with increasing LED die
junction temperature. Accordingly, there is a well-recognized need
for reducing LED die junction temperatures in LED flashlights to
increase performance.
[0004] The present invention discloses and teaches a much improved
LED lighting device, preferably with an outer metallic flashlight
housing or barrel, which achieves superior performance through
improved heat control of LED die junction temperature via an
improved heatsink assembly.
SUMMARY OF THE INVENTION
[0005] The present invention is generally directed to a lighting
device, such as a flashlight, having heatsink technology in which
one electrically conductive pad of an LED package is thermally and
electrically bonded to an inner electrically conductive member
which is positioned and electrically isolated from an outer
electrically conductive member by electrically insulating material
and a second electrically conductive pad and the thermal pad of the
LED package are thermally and electrically bonded (such as by use
of solder) to the outer electrically conductive member so that heat
is transferred from an LED die within the LED package to the outer
electrically conductive member and then to a thermally conductive
outer casing with a thermal path in which thermal resistance is
minimized.
[0006] Accordingly, it is a primary object of the present invention
to provide improved heatsink technology.
[0007] This and further objects and advantages will be apparent to
those skilled in the art in connection with the drawings and the
detailed description of the invention set forth below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 illustrates a surface mount LED package, such as a
Cree.RTM. XLamp.RTM. XP-G2 LED, which constitutes prior art, and
FIG. 1A is an exploded assembly view of FIG. 1.
[0009] FIGS. 2A-E illustrate a prior art LED assembly showing the
LED soldered to a PC board. FIG. 2B is a cross sectional view which
is shown exploded in FIG. 2E while FIGS. 2A and 2C are,
respectively, top and bottom views looking into the apparatus shown
in cross section in FIG. 2B, and FIG. 2D is an enlarged cutaway
view of FIG. 2B.
[0010] FIGS. 3A-D illustrate a widely used prior art star type,
metal and ceramic backed PC board to which the LED is mounted for
use in a flashlight. FIG. 3B is a cross sectional view which is
shown exploded in FIG. 3D while FIGS. 3A and 3C are, respectively,
top and bottom views looking into the apparatus shown in cross
section in FIG. 3B.
[0011] FIGS. 4A-D illustrate a heatsink assembly in accordance with
one embodiment of the present invention installed in a metal tube
or flashlight barrel. FIG. 4B is a cross sectional view which is
shown exploded in FIG. 4A while FIGS. 4C and 4D are, respectively,
top and bottom views looking into the apparatus shown in cross
section in FIG. 4B.
[0012] FIGS. 5A-D illustrate a variation on the heatsink assembly
shown in FIGS. 4A-D.
[0013] FIGS. 6A-D illustrate a variation on the heatsink assembly
shown in FIGS. 4A-D in which a printed circuit board (PCB) is held
within the heatsink assembly.
[0014] FIGS. 7A-D illustrate a circular array of LEDs mounted on a
common heatsink assembly. Four LEDS are shown, but there could be
any number of LEDs. FIG. 7B is a cross sectional view which is
shown exploded in FIG. 7A while FIGS. 7C and 7D are, respectively,
top and bottom views looking into the apparatus shown in cross
section in FIG. 7B.
[0015] FIGS. 8 and 9 are block diagrams of a heatsink mounted LED
with positive and negative polarity heatsinks, respectfully, while
FIGS. 10 and 11 illustrate the same heatsink mounted LED positive
and negative polarity heatsinks that incorporate a PCB with LED
drive electronics.
[0016] FIGS. 12A-G illustrate manufacture of a heatsink assembly in
accordance with one embodiment of the present invention. FIG. 12C
is a cross sectional view of the heatsink assembly, which is shown
enlarged in FIG. 12E. FIG. 12A illustrates insertion of a molded
piece, containing parts 72 and 73 (which are shown enlarged in FIG.
12G), into a cavity of heat sink 71, after which an LED package is
soldered to the assembly by applying solder to solder points S1P
and S2P illustrated in FIG. 12B, while FIG. 12F illustrates the
heat sink assembly after an epoxy has been used to firmly secure
the parts held within the cavity. It should be noted that the
thickness of S1 and S2 shown in FIGS. 12C and 12E has been
exaggerated so that they are visibly discernable. FIG. 12D is an
enlarged view of FIG. 12B.
[0017] FIGS. 13A-B illustrate a process for manufacturing a
heatsink assembly in accordance with the present invention in which
solder is used to solder pads of an LED assembly to a top surface
of an outer electrically conductive member to form a heatsink
assembly while FIGS. 13C-D illustrate a press fit step of inserting
a heatsink assembly into a tube or barrel.
[0018] FIGS. 14A-B illustrate variations on FIGS. 13D in which the
heatsink assembly is secured to a tube or barrel by use of
mechanical retention means rather than a press fit.
[0019] FIG. 15 is an exploded view which illustrates an LED
flashlight with an improved heatsink in accordance with the present
invention while FIG. 16 is a cross sectional view of the head
portion of the LED flashlight shown in FIG. 15 in an assembled
state.
DETAILED DESCRIPTION OF THE INVENTION
[0020] In the Figures and the following detailed description,
numerals indicate various physical components, elements or
assemblies, with like numerals referring to like features
throughout both the drawings and the description. Although the
Figures are described in greater detail below, the following is a
glossary of elements identified in the Figures.
[0021] 1 flashlight
[0022] 11 barrel of flashlight 1
[0023] 11A shoulder of barrel 11
[0024] 11AT top surface of shoulder 11A
[0025] 11B nut
[0026] 42 lip seal
[0027] 51 tail cap
[0028] 51 outer member of tail cap
[0029] 58 spring
[0030] 70 heatsink assembly
[0031] 70A heatsink assembly with PCB held in core material
[0032] 71 outer electrically conductive member of heatsink assembly
70
[0033] 71C cavity formed in outer electrically conductive member
71
[0034] 71K keyway in outer electrically conductive member 71
[0035] 71OP opening in top surface 71T
[0036] 71T top surface of outer electrically conductive member
71
[0037] 72 core of an electrically insulating material of heatsink
assembly 70
[0038] 72A upper portion of core of an electrically insulating
material of heatsink assembly 70A
[0039] 72B lower portion of core of an electrically insulating
material of heatsink assembly 70A
[0040] 72E epoxy
[0041] 72P passageway formed in core 72 into which epoxy 72E is
flowed
[0042] 73 inner electrically conductive member of heatsink assembly
70
[0043] 73A upper portion of inner electrically conductive member of
heatsink assembly 70A
[0044] 73B lower portion of inner electrically conductive member of
heatsink assembly 70A
[0045] 73T top surface of inner electrically conductive member
73
[0046] 74 thermal junction and electrical connection between LED
package 120 and outer electrically conductive member 71
[0047] 75 electrical connection between LED package 120 and inner
electrically conductive member 73
[0048] 76 thermal junction between outer electrically conductive
member 71 and barrel 11 printed circuit board
[0049] 77EAR ear for engaging PCB 77
[0050] 77T trace on PCB 77
[0051] 100 battery
[0052] 120 LED package
[0053] 121 LED die of LED package 120
[0054] 122 silicon sub-mount of LED package 120
[0055] 123 heat conductive material of LED package 120
[0056] 124 wire bond of LED package 120
[0057] 125 contact pad of LED package 120
[0058] 126 contact pad of LED package 120
[0059] 127 contact pad of LED package 120
[0060] 128 outer casing of LED package 120
[0061] 129 clear dome of LED package 120
[0062] 173 electrical contact between 77EAR and 77T
[0063] 402 heatsink
[0064] 403 insulator
[0065] 404 contact for supplying power to PCB
[0066] 406 housing
[0067] 407 insulator
[0068] 408 contact for connecting PCB 111 to PCB 109
[0069] 409 multilayered PCB
[0070] 410 ring contact
[0071] 411 PCB
[0072] 426 first power connection
[0073] 427 second power connection
[0074] 428 star PCB
[0075] 500 face cap
[0076] 501 O-ring
[0077] 502 lens
[0078] 503 reflector
[0079] 504 threaded nut
[0080] 505 retaining ring
[0081] 506 O-ring
[0082] 508 O-ring
[0083] 509 internal snap ring
[0084] 510 actuator
[0085] 511 switch port seal
[0086] 512 switch
[0087] S1 solder
[0088] S1P solder point for solder S1
[0089] S2 solder
[0090] S2P solder point for solder S2
[0091] The present invention is generally applicable to many
different types of lighting devices, an especially preferred
embodiment of which is flashlights having an outer metallic casing,
examples of which are described in U.S. Pat. Nos. 6,361,183 and
8,366,290, the disclosures of which are specifically incorporated
by reference herein. Hereinafter, the invention will be illustrated
by use of a flashlight without limiting the invention solely to
such an embodiment.
[0092] Metallic flashlights have been using one or more light
emitting diodes ("LEDs") as a light source for a number of years.
LEDs can be purchased from a number of suppliers, one example of
which is Cree, and for purposes of illustration, Cree.RTM.
XLamp.RTM. XP-G2 LEDs can be used as suitable LEDs.
[0093] An LED useful in the present invention is illustrated in
FIGS. 1 and 1A, in which an LED package 120 has an LED die 121
located on top of a silicon sub-mount 122 which is located atop a
heat conductive material 123 while the bottom of LED package 120
has three surface mount contact pads 125, 126 and 127, heat
conductive material 123 being held within an outer casing 128,
there being a clear dome 129 placed around and above die 121. One
of contact pads 125 and 127 is a positive contact pad, the other is
a negative contact pad, while contact pad 126 is neither a negative
or positive pad, but a thermal pad which is configured to
facilitate transfer of heat from die 121 through heat conductive
material 123 outside of LED package 120 via thermal pad 126. The
positive and negative contact pads (125, 127) are electrically
connected to die 121 via two wire bonds 124. The details of the
sub-construction of LED package 120 are not critical to the present
invention, and die 121, sub-mount 122 and heat conductive material
123 might be manufactured by a process in which they are integrally
formed on a wafer; similarly, the details of how the positive and
negative contact pads of LED package 120 are electrically isolated
from one another are not critical to the present invention and a
variety of different LED package structures might be suitable for
use with the present invention, including LED package structures
with five or more contact pads. What is important is that there are
positive and negative electrically conductive pads to provide power
to cause a die within the LED package to emit light and that any
heat removal mechanism within the LED package can be thermally
connected to an outer electrically conductive member of a heatsink
assembly 70 via a thermal pad, as explained below.
[0094] A heatsink assembly 70 according to the present invention
has three main parts--an outer electrically conductive member 71
that is thermally conductive and which is mechanically connected to
an outer casing of a lighting apparatus (e.g., a barrel 11 of a
flashlight 1), a core 72 of an electrically insulating material
which is held within a cavity formed in outer electrically
conductive member 71 and one or more inner electrically conductive
members 73 which is/are positioned and electrically isolated from
outer electrically conductive member 71 by core 72. It is
especially preferred that outer electrically conductive member 71
maintains thermal and mechanical connection to barrel 11 by a
mechanical contact (such as a press fit, nut and thread connection,
or some other mechanical means).
[0095] LED package 120 is thermally and electrically connected to
heatsink assembly 70 so that LED package 120 is turned on when
power from an electrical circuit is applied to outer electrically
conductive member 71 and inner electrically conductive member
73.
[0096] FIGS. 4A through 7D depict variations on the inventive
design of the present invention. As shown, heatsink assembly 70 can
be of different shapes depending upon the application. Heatsink
assembly 70 can also support multiple LED packages 120 in a variety
of configurations (see, e.g., FIGS. 7A-D); a circular array and a
linear are only two of many possibilities. When multiple LED
packages 120 are used with a single heatsink assembly 70, multiple
inner electrically conductive members 73 can be used, one for each
LED package 120, or multiple LED packages 120 can be bonded to a
single inner electrically conductive member 73. Electronics with a
suitable interconnect method can also be suspended in insulating
core 72. For example, as illustrated in FIGS. 6A-D, PCB 77 with
four traces 77T on each of its planar sides (see FIG. 6A which
illustrates one side) is held by upper and lower portions 73A and
73B, each of which has four ears 77EARs for engaging four traces
77T, which provide multiple electrical paths for completing an
electrical circuit to power up LED package 120. It is also possible
in all cases to provide electrically insulating material that
positions and electrically isolates two electrically conductive
members that extend out of the end opposite from LED package 120 to
provide electrical connection points. In these cases the cathode
and anode LED package pads are bonded to corresponding isolated
pads and the LED package thermal pad is bonded to electrically
conductive member 71.
[0097] The improved heatsink assemblies illustrated in FIGS. 4A
through 7D do not utilize a PC board for mounting a LED package
120; instead, LED package 120 is mounted directly to metal top
surface 71T of outer electrically conductive member 71 and metal
top surface 73T of inner electrically conductive member 73. This
method produces much improved heat transfer and a cooler operating,
higher lumens LED package 120, compared to PC board mounted LED
designs.
[0098] The present invention provides a direct efficient path to
conduct heat away from an LED package to ambient air outside of a
flashlight or any other lighting device such as a headlamp, lantern
or spotlight, as well as all types of area lighting that utilize
high powered LEDs as a light source. Other heatsinking methods
produce thermal paths that include a large number of thermal
junctions, some of which have poor thermal conductivity or high
thermal resistance. Examples of prior art heatsinking methods are
illustrated in FIGS. 2A through 3D. Unique to the present invention
is the ability to solder the heatsink component, which is outer
electrically conductive member 71, directly to the electrical and
thermal pads of LED package 120. No thermal grease or adhesives are
required. In other designs heatsinking and electrical contact pads
are on a PC board which results in more, less efficient, thermal
junctions and longer, smaller cross section, thermal paths to
ambient air. The use of thermal grease and adhesives in these less
efficient designs helps heat transfer to some degree but not to the
level of attaching the LED package directly to the heatsink
assembly. The result of the much improved heat transfer possible
with the invention is that the LED package operates much cooler and
therefore much more efficiently. Higher lumens are possible with no
increase in power over conventional systems. It is also possible to
maintain lumens at the same level as other less efficient systems
but consume far less power. This is especially important in battery
powered lighting systems as on-time is extended without reducing
lumens.
[0099] It is worth noting that the efficiency of the present
invention can be increased or optimized, with the aid of the
present disclosure, by increasing or maximizing the surface area
exposure between the heatsink component of the heatsink assembly
and the thermally and electrically conductive outer casing while
also designing the heatsink component to have a sufficient mass to
effectively and efficiently conduct heat between the heatsink
assembly and the outer casing.
[0100] It is also worth noting that the outer casing, which is
illustrated in the exemplary embodiments depicted in FIGS. 4-7D as
a tube or barrel, need not be thermally and electrically conductive
over its entire outer surface, although an outer casing which is
thermally and electrically conductive over its entire outer surface
may achieve better results.
[0101] Core 72 of the present invention is, in an especially
preferred embodiment, molded with inner electrically conductive
member 73 in place, to form a single assembly, which is inserted
into a cavity 71C formed in outer electrically conductive member 71
so that passageway 72P is formed between core 72 and outer
electrically conductive member 71 in cavity 72C which is then
filled with epoxy 72E to securely hold core 72 within cavity 72C
and precisely position top surface 73T in opening 71OP of top
surface 71T so that top surface 73T of inner electrically
conductive member 73 is accessible for soldering to a contact pad
of LED package 120 to form electrical connection 75. Epoxy 72E may
be comprised of an adhesive or material made from a class of
synthetic thermosetting polymers containing epoxy groups which
function as a glue or be made of any other material suitable for
being flowed or injected into passageway 72P which will then harden
and function to glue core 72 to outer electrically conductive
member 71 within cavity 71C. It is especially desirable that outer
electrically conductive member 71 include an additional mechanical
means for holding core 72 within cavity 71C, one example of which
is to include one or more keyways 71K that will form mechanical
retention mechanisms once passageway 72P is filled with epoxy
72E.
[0102] After core 72 is secured within cavity 71C, heatsink
assembly 70 is created by soldering a thermal pad and an
electrically conductive pad of LED package 120 to top surface 71T
of heatsink component 71. Commercially available LEDs typically
have three or more pads (see, e.g., FIG. 1A which illustrates three
pads) which can all be used for soldering (solder S1 in FIG.
[0103] 13A is for one pad whereas solder S2 in FIG. 13A is for two
pads). FIG. 12B illustrates solder points S1P and S2P for solder S1
and S2.
[0104] Outer electrically conductive member 71 serves as the
heatsink component of heatsink assembly 70 and its top surface 71T
(see FIG. 4C) provides a mounting surface for LED package 120. The
anode or cathode contact pad of LED package 120, as well as a
dedicated thermal pad (e.g., 126 of FIG. 1A), are bonded to top
surface 71T by soldering or some other thermally and electrically
conductive method or material while the electrically opposite side
of LED package 120 is bonded to top surface 73T of inner
electrically conductive member 73. Heat generated by LED die 121 is
conducted through sub-mount 122 to heat conductive material 123 to
thermal pad 126 and one of pads 125, 127 where it is conducted
through thermal junction 174 to outer electrically conductive
member 71 and then through thermal junction 76 to barrel 11 to
ambient air. LED package 120 runs much cooler and more efficiently
in this system than is possible when LED package 120 is mounted on
printed circuit boards (such as is shown in FIGS. 2A-3D) because of
lower thermal resistance of the system. Thermal resistance is a
heat transferring property of an overall system irrespective of the
source of heat which is measured in the system's increase in
temperature per unit of conducted heat energy, such as .degree.
C./W.
[0105] Once heatsink assembly 70 is created, it can be press fit
into a tube or barrel 11 as illustrated in FIGS. 13C and 13D or it
can be removably inserted into tube or barrel 11 and then be held
in place by a removable holding mechanism, an example of which is
nut 11B illustrated in FIG. 14A and 14B. In the embodiments
illustrated in FIGS. 14A and 14B, in an especially preferred
embodiment, tube or barrel 11 and heatsink component 71 are made of
aluminum, heatsink component 71 is coated with a metallic plating
(e.g., nickel) that helps promote the soldering process, and a skin
cut is made of the anodized aluminum where heatsink component 71
comes into contact with a top surface 11AT of shoulder 11A formed
in tube or barrel 11 (so as to promote more efficient thermal heat
transfer and for electrical conductivity). Also, it is especially
desirable that heatsink assembly 70 be designed so that it can
receive a reflector 503 (see FIG. 16) so that LED package 120 is
positioned within reflector 503 facing outwardly from a head end of
barrel 11.
[0106] When heatsink assembly 70 is held by mechanical contact with
barrel 11, a thermal path is created between the thermal pad and
one contact pad of LED package 120 which is bonded to electrically
conductive member 71 and barrel 11 which has a first thermal
junction 74 between said thermal pad and one contact pad of LED
package 120 and outer electrically conductive member 71 and a
second thermal junction 76 between outer electrically conductive
member 71 and barrel 11 (see FIG. 4B). Minimizing the number of
thermal junctions between LED package 120 and barrel 11 helps to
minimize thermal resistance.
[0107] To demonstrate the lower thermal resistance obtainable by
use of the heatsink technology of the present invention, tests were
performed between different heat sink systems for use in a tube
sized to accommodate a c-cell size battery. For each device under
test (DUT), an LED package from the same family of LEDs was mounted
on a heatsink system as noted below which was then pressed into a
piece of aluminum of the same size and diameter to create the DUT,
with the DUTs assembled as follows.
[0108] The UNI Module DUT used a heatsink system that corresponds
to what is depicted in FIGS. 2A-E in which the heatsink module was
pressed into aluminum which was then pressed into the tube of
aluminum.
[0109] The Starboard DUT used a heatsink system that corresponds to
what is depicted in FIGS. 3A-D in which the starboard was screwed
onto a piece of aluminum with thermal grease located between the
starboard and the piece of aluminum, and then this assembly was
pressed into the tube of aluminum.
[0110] The 0.070'' AL Molded DUT used a heatsink system that
corresponds to what is depicted in FIGS. 4A-D in which outer
electrically conductive member 71 is made out of aluminum with a
thickness of 0.070 inches while the 0.070'' Cu Molded DUT is the
same heatsink system made out of copper instead of aluminum.
[0111] The Solid AL Molded DUT used a heatsink system that
corresponds to what is depicted in FIGS. 5A-D while the Solid Cu
DUT is the same heatsink system made out of copper instead of
aluminum.
[0112] The DUTs were tested using the following testing methodology
to obtain the test results set forth in Table 1: [0113] Measure LED
solder point temperature {T.sub.sp}. A precision thermocouple (Type
J or Type K) is placed directly adjacent to LED package on the
surface of the heatsink. [0114] DUT is powered from a digitally
controlled power source at desired current level {I.sub.LED} and is
recorded for later calculations [0115] DUT is powered on long
enough for solder point temperature to stabilize (usually 30 to 45
minutes). Temperature is measured and logged using precision data
acquisition instrument. Once peak temperature is observed, it is
recorded as {T.sub.sp} [0116] Measure LED Forward Voltage {V.sub.f}
at desired current level {I.sub.LED} when peak {T.sub.sp} is
observed. The LED Voltage {V.sub.f} is measured using a precision
volt meter connected directly to the LED solder pads [0117] Total
LED Power Dissipation {P.sub.d} is calculated using equation 1. LED
current {I.sub.LED} multiplied by measured LED Forward Voltage
{V.sub.f}. [0118] Calculate thermal resistance {.THETA..sub.Rth}
using equation 2. This is the total thermal resistance of the heat
sink and flashlight barrel, from LED solder point {T.sub.sp} to
ambient air {T.sub.amb} [0119] Obtain manufacturer's thermal
resistance {.THETA..sub.RthLED} specification for the LED family
being used. In this case, the Cree XM-L2 is 2.5.degree. C./W.
[0120] Calculate LED junction temperature {T.sub.j} using equation
3. This is the temperature of LED die, also called LED
junction.
Equations:
[0121] P.sub.d=I.sub.LED*V.sub.f 1.
.THETA..sub.Rth=(T.sub.sp-T.sub.amb)/P.sub.d 2.
T.sub.j=(P.sub.d*.THETA..sub.RthLED)+T.sub.sp 3.
[0122] Definitions of Variables and Constants: [0123]
.THETA..sub.Rth=Calculated Thermal resistance of heat sink (overall
thermal resistance, from T.sub.sp to ambient air T.sub.amb)
[.degree. C./W] [0124] T.sub.sp=Solder point temperature (measured
directly adjacent to LED substrate) [.degree. C.] using
thermocouple [0125] T.sub.amb=Ambient air temperature [.degree. C.]
[0126] P.sub.d=Total calculated dissipated power [W] [0127]
I.sub.LED=LED drive current [A] [0128] V.sub.f=LED forward voltage
[V] [0129] T.sub.j=Calculated LED Junction temperature [.degree.
C.] [0130] .THETA..sub.RthLED=Manufacturer specified thermal
resistance of LED family [.degree. C./W] XM-L2 LED: 2.5.degree.
C./W
TABLE-US-00001 [0130] TABLE 1 V.sub.f P.sub.d T.sub.sp
.THETA..sub.Rth T.sub.j Device Under Test (DUT) [V] [W] [.degree.
C.] [.degree. C./W] [.degree. C.] UNI Module 3.16 9.48 164 14.66
187.7 Starboard 3.27 9.81 95 7.14 119.53 Solid flat Al 3.28 9.84 92
6.81 116.6 .070'' Al Molded 3.29 9.87 87 6.28 111.68 Solid Al 3.29
9.87 86 6.18 110.68 Solid Cu 3.29 9.87 83 5.88 107.68 .070'' Cu
Molded 3.3 9.9 80 5.56 104.75 Constants T.sub.amb = 25.degree. C.
I.sub.LED = 3 A .THETA..sub.RthLED = 2.5.degree. C./W
[0131] In calculating the results set forth in Table 1, it was
assumed that 100% of total power is dissipated as heat. This is the
absolute worst case scenario because, in a real world application,
only about 60-70% of the total power is dissipated as heat, while
the remaining 30-40% is converted to photon energy (light), but
it's nearly impossible to know the precise efficacy (ability to
convert electrical power to photon energy) of each LED, so 100%
power dissipation was used for the worst case scenario.
[0132] It should also be noted that tests were made on a heatsink
system that corresponds to what is depicted in FIGS. 4A-D with a
smaller thickness of aluminum of 0.050 inches, but the results of
that test, while superior to the UNI Module DUT, were not superior
to that of the Starboard DUT, thus emphasizing the need for
ensuring that outer electrically conductive member 71 is
sufficiently thick so as to efficiently conduct heat away from the
LED package.
[0133] While the invention has been described herein with reference
to certain preferred embodiments, those embodiments have been
presented by way of example only, and not to limit the scope of the
invention. Additional embodiments will be obvious to those skilled
in the art having the benefit of this detailed description.
[0134] Accordingly, still further changes and modifications in the
actual concepts descried herein can readily be made without
departing from the spirit and scope of the disclosed inventions as
defined by the following claims.
* * * * *