U.S. patent application number 11/538790 was filed with the patent office on 2007-04-19 for led assembly with vented circuit board.
This patent application is currently assigned to ONSCREEN TECHNOLOGIES, INC.. Invention is credited to Nilesh Thakor Desai, Steven Flank, Robert Bogdan Raos.
Application Number | 20070086189 11/538790 |
Document ID | / |
Family ID | 34963444 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070086189 |
Kind Code |
A1 |
Raos; Robert Bogdan ; et
al. |
April 19, 2007 |
LED Assembly with Vented Circuit Board
Abstract
A light emitting diode (LED) assembly with a vented printed
circuit board is disclosed. A printed circuit board assembly may
include a plurality of LED modules disposed in an array with a
multilayered substrate and a plurality of vents. The multilayer
substrate may include a thermal cooling layer which is in thermal
communication with the LED modules for heat dissipation. The
multilayer substrate may include one or more electrical power
layers in electrical communication with the LED modules for
energizing the LEDs. The multilayered substrate may have an
external insulating layer that includes a plurality of fluid
apertures configured for fluid communication with the thermal
cooling layer.
Inventors: |
Raos; Robert Bogdan; (Monte
Sereno, CA) ; Desai; Nilesh Thakor; (San Jose,
CA) ; Flank; Steven; (Washington, DC) |
Correspondence
Address: |
BANNER & WITCOFF
1001 G STREET N W
SUITE 1100
WASHINGTON
DC
20001
US
|
Assignee: |
ONSCREEN TECHNOLOGIES, INC.
200 9th Avenue North Suite 210
Safety Harbor
FL
|
Family ID: |
34963444 |
Appl. No.: |
11/538790 |
Filed: |
October 4, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10847343 |
May 18, 2004 |
7138659 |
|
|
11538790 |
Oct 4, 2006 |
|
|
|
Current U.S.
Class: |
362/249.01 ;
257/79 |
Current CPC
Class: |
H05K 2201/10106
20130101; H05K 3/28 20130101; H05K 2203/1178 20130101; H05K
2201/1056 20130101; H05K 2203/081 20130101; G09F 13/20 20130101;
G09F 9/33 20130101; H05K 1/0209 20130101; H05K 2201/0989 20130101;
H05K 2201/064 20130101 |
Class at
Publication: |
362/249 ;
257/079 |
International
Class: |
F21V 21/00 20060101
F21V021/00; F21V 29/00 20060101 F21V029/00; H01L 29/00 20060101
H01L029/00 |
Claims
1. A circuit board LED display assembly, comprising: a plurality of
LEDs having a dome, the LEDs being disposed in a grid pattern at
junctions, the junctions being connected by bridges defining air
vents through which air can flow through the printed circuit board
assembly; the bridges formed from a substrate for activating the
LEDs, the substrate having a first side including the LEDs and an
opposing a second side; and a plurality of aerodynamic members
configured to reduce air pressure, the aerodynamic members being
disposed on the second side of the substrate corresponding to the
junctions.
2. The circuit board LED display assembly according to claim 1,
wherein the substrate comprises a multilayered substrate having a
thermal cooling layer in thermal communication with the LEDs.
3. The circuit board LED display assembly according to claim 2,
wherein the multilayered substrate includes an insulating layer
over the thermal cooling layer; and insulating layer having a
plurality of openings configured for air communication with the
thermal cooling layer.
4. The circuit board LED display assembly according to claim 3,
wherein said openings are disposed in a sidewall of the bridges for
exposing a portion of the thermal cooling layer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 10/847,343, filed May 18, 2004 and entitled
"LED Assembly with Vented Circuit Board," the contents of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention relates to lighting units using light emitting
diodes (LEDs). More particularly, the invention relates to a light
emitting diode assembly with a vented circuit board.
BACKGROUND OF THE INVENTION
[0003] Light-emitting diodes (LEDS) have been used for signs and
other types of illuminated displays for many years. As a byproduct
of operation, display assemblies having LEDs generate heat as
electric current flows through the devices. The heat must be
dissipated or removed to prevent overheating. Cooling a display
assembly is important in order to preserve its functionality and
efficiency. Furthermore, display assemblies when used in outdoor
environments may be exposed to wind forces that affect loading on
the assemblies. One approach for cooling an LED display assembly is
shown in PCT publication WO2004019657. The publication generally
shows a coolant fluid which cools LEDs using a mesh design.
BRIEF SUMMARY OF THE INVENTION
[0004] In one variation, a printed circuit board assembly includes
a plurality of LEDs disposed in a grid pattern at junctions in
which the junctions are interconnected by adjacent bridges defining
air vents. A plurality of vents enables air to pass through the
printed circuit board assembly, thus reducing wind resistance and
promoting cooling.
[0005] In another variation, a printed circuit board assembly
includes a plurality of LED modules, each LED module being disposed
at a corresponding junction, the junctions being connected to
bridges in which adjacent bridges define air vents for allowing air
to pass through. The bridges and junctions include a multilayer
substrate having an insulating layer and a thermal cooling layer in
thermal communication with the LED modules. The insulating layer
may include a plurality of fluid openings configured for fluid
convective heat transfer with the thermal cooling layer.
[0006] In yet another variation, a printed circuit board assembly
includes a plurality of LED modules and a multilayer substrate. The
multilayered substrate may have an external insulating layer and a
thermal cooling layer in thermal communication with the LED
modules. The external insulating layer includes a plurality of
openings which exposes the thermal cooling layer for fluid
convective heat transfer.
[0007] In yet another variation, a printed circuit board assembly
includes a plurality of LEDs having a dome. The LEDs may be
disposed in a grid pattern at junctions being interconnected by
bridges defining air vents. The bridges include a substrate for
activating the LEDs and the substrate includes a front side
including the LEDs and an opposing a rear side. Aerodynamic members
configured to reduce air pressure are disposed on the second side
of the substrate corresponding to location of the junctions. In
this way, wind loading may be reduced for multiple directions.
Other variations are described in more detail herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] A more complete understanding of the present invention and
the advantages thereof may be acquired by referring to the
following description in consideration of the accompanying
drawings, in which like reference numbers indicate like features,
and wherein:
[0009] FIG. 1 illustrates a perspective view of a printed circuit
board assembly according to one or more aspects of the present
invention.
[0010] FIG. 2 illustrates a frontal elevation view of the printed
circuit board assembly of FIG. 1.
[0011] FIG. 3 illustrates an enlarged view of the printed circuit
board assembly of FIG. 1 with LED modules.
[0012] FIG. 4 illustrates an enlarged view of a printed circuit
board assembly similar to FIG. 3, with the LED modules according to
one or more aspects of the present invention.
[0013] FIG. 5 illustrates a first rear perspective view of an LED
module according to one or more aspects of the present
invention.
[0014] FIG. 6 illustrates a front perspective view of the LED
module of FIG. 5 according to one or more aspects of the present
invention.
[0015] FIG. 7 illustrates a second rear perspective view of a LED
module according to one or more aspects of the present
invention.
[0016] FIG. 8 illustrates a perspective view of an alternative
embodiment of a printed circuit board assembly according to one or
more aspects of the present invention.
[0017] FIG. 9 illustrates a schematic diagram of one possible
decoder-conductor arrangement for energizing components of a LED
module according to one or more aspects of the present
invention.
[0018] FIG. 10 illustrates an enlarged view of the PCB assembly of
FIG. 1 with a first heat dissipation feature according to one or
more aspects of the present invention.
[0019] FIG. 11 illustrates an enlarged view of the PCB assembly of
FIG. 1 with a second heat dissipation feature according to one or
more aspects of the present invention.
[0020] FIG. 12 illustrates an enlarged view of the PCB assembly of
FIG. 1 with a third heat dissipation feature according to one or
more aspects of the present invention.
[0021] FIG. 13 illustrates a partial schematic section view of the
printed circuit board assembly taken along line 13-13 of FIG.
10.
[0022] FIG. 14 illustrates a schematic diagram of a conductor-LED
module arrangement according to one or more aspects of the present
invention.
[0023] FIG. 15 illustrates a partial schematic section view of an
alternative multilayer substrate arrangement according to one or
more aspects of the present invention.
[0024] FIG. 16 illustrates a partial schematic section diagram of
an alternative multilayer substrate arrangement according to one or
more aspects of the present invention.
[0025] FIG. 17 illustrates a partial schematic diagram of an
alternative PCB assembly according to one or more aspects of the
present invention.
[0026] FIG. 18 illustrates a partial schematic diagram of a PCB
assembly with roughness members according to one or more aspects of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0027] In the following description of the various embodiments,
reference is made to the accompanying drawings, which form a part
hereof, and in which is shown by way of illustration various
embodiments in which the invention may be practiced. It is to be
understood that other embodiments may be utilized and structural
and functional modifications may be made without departing from the
scope of the present invention.
[0028] FIGS. 1-4 illustrate an embodiment of a printed circuit
board (PCB) assembly 2 including an array or grid pattern of light
emitting diode (LED) modules 4 mounted thereon. In one arrangement,
the LED modules 4 are disposed at intersecting junctions 5 of the
PCB assembly 2 in a generally perpendicular X-direction and
Y-direction based on a Cartesian coordinate system. The junctions 5
(see FIG. 3) are interconnected by a plurality of bridges 17
defining vents 22, which may be drilled or routed in the printed
circuit board. While the terminology "printed circuit board" is
used for ease of reference, it should be understood that other
types of circuit boards other than printed boards may be used, and
such boards are intended to be encompassed within the term "printed
circuit board" or PCB. Examples may include embedded wires, ribbon
cables, or similar structures.
[0029] FIGS. 5-7 illustrate an embodiment of an LED module 4
according to one or more aspects of the present invention. LED
module 4 may include one or more LEDs 6a-d disposed within the
interior cavity of a removable translucent dome or cap 8. The cap
is optional and may not be required in all applications. Moreover,
while four LEDs 6a-d are shown, the LED module 4 may have more or
fewer LEDs depending on the acceptability for the intended use. In
one variation, an LED module may consist of a single LED
mechanically attached by, for example, soldering to the circuit
board.
[0030] The dome 8 may be formed of several alternative materials,
such as a translucent plastic or glass. Various materials may be
selected for atmospheric environments based on the intended use. An
appropriate material and thickness characteristics enables the dome
8 to protect the LED 6a-d against physical impingement from flying
projectiles in the air or rain, and may help in reducing
aerodynamic drag on the assembly. Dome 8 can be optically neutral
to preserve the optical characteristics of the LED 6a-d, such as
field-of-view focusing. Alternatively, dome 8 may also have optical
properties that enhance those of the LED 6a-d, such as lowering the
side leakage. The material may also protect the LEDs 6a-d from UV
damage that may discolor the optical material or other internal
components. The UV protection helps to mitigate brightness
reduction of the LEDs 6a-d over time due to exposure to external UV
wavelengths. The dome 8 may be removably mounted via a friction-fit
engagement to a base member 10. Alternatively, dome 8 may be
mounted to the base member 10 in other ways, such as in a snap-fit
or threaded engagement. The removable arrangement of the dome 8
provides access for field or bench-level maintenance, such as
replacement or upgrade to the LED 6a-d or other components of LED
module 4. LED modules may be removed from the PCB assembly for
maintenance and the like.
[0031] Various techniques may be implemented to permit an LED
module to be serviced without being completely removed. For
example, the LED module may be attached to the board by a hinge or
similar mechanism such that it can be opened without being
removed.
[0032] In one variation, base member 10 includes extension members
or protrusions 12 that may be utilized for mounting the LED module
4 to the PCB assembly 2. In one configuration, the extension
members 12 may provide a partial heat transfer path for cooling the
LED module 4 in conjunction with PCB 2 assembly substrates. The
base member 10 may be composed of a number of alternative
materials, including copper, aluminum, or a mixture of metal
particulates suspended in a plastic material, carbon fibers or
other well known material that provides thermal conductivity
without electrical connection.
[0033] With continued reference to FIGS. 5-7, in one arrangement,
the base member 10 may have an annular or circular shape.
Alternatively, base member 10 may be formed in several shape
configurations depending on the intended use of the LED module 4. A
peripheral surface of the base member 10 may retain a sealing
member 14. The sealing member 14 may be configured to prevent
debris and other external environmental components from entering
into the interior cavity of the LED module 4 formed between the
dome 8 and base member 10. The sealing configuration with the dome
8 also provides protection of the LEDs 6a-d against environmental
conditions, such as temperature, humidity, salt, acid rain and the
like. The sealing member 14 can be formed in several shapes and
mounted to the base member 10 using conventional methods and
techniques. For example, the sealing member 14 can be formed as an
annular ring, such as an O-ring. Further, the sealing member 14 may
be composed of a resilient material, such as rubber or a synthetic
rubber. For mounting arrangements, the sealing member 14 may be
adhesively bonded to the base member 10. Alternatively, the sealing
member 14 can provide compression forces for a friction fit
engagement with the base member 10.
[0034] With reference to FIGS. 5 and 7, each LED 6a-d includes two
electrical leads 16 physically connected to respective electrical
conductors. Lead material and length may be selected to maximize
thermal connection between LED and circuit board for heat
dissipation, as discussed in more detail below. While leads 16 are
shown, the LED module may have other alternative configurations.
For example, the LED module may be surface mounted or a
direct-on-die arrangement on the PCB assembly substrate. In such a
surface mount configuration, the leads are connected to electrical
conductors or traces.
[0035] In the most basic configuration, a single LED may be placed
at each junction, and may be selectively illuminated by energizing
a corresponding X-wire conductor and Y-wire conductor, such that
the LED at the junction of the X-wire conductor and Y-wire
conductor causes the LED to be illuminated. In other embodiments,
more than one LED may be affixed to each junction, such that a
single X-wire conductor and Y-wire conductor when energized cause
all of the LEDs at the junction to be illuminated. In yet other
embodiments, a plurality of X-wire conductors and a plurality of
Y-wire conductors (e.g., two in each direction) overlap at the
junction, such that more than one pair of conductors is available
to selectively illuminate one or more LEDs at the junction. Drivers
of various types may be used in association with the LEDS, such
that signaling is provided on one set of conductors while power is
provided by means of other conductors.
[0036] In some embodiments, multiple LEDs at the junction may be
selectively energized by means of a decoder that decodes signals on
corresponding X-wire conductors and Y-wire conductors such that a
larger number of LEDs can be selectively illuminated using a
smaller number of conductors.
[0037] The LED module 4 may include a decoder unit 18 which may be
configured for control of energizing or de-energizing each
respective LED 6a-d through MOSFET gating or other means. Each
decoder unit 18 may be responsive to computer readable commands
intended for controlling each LED 6a-d. Alternatively, each LED
6a-d within the module 4 may be energized simultaneously for
increased illumination and brightness characteristics depending on
the intended application. For example, applications that may
utilize the PCB assembly 2 could be a vehicular or aircraft traffic
signage; large screen video displays; and computerized video
billboards and the like.
[0038] In the arrangement shown in FIGS. 5 and 7, each decoder unit
18 may have six leads for various logic control functions with a
computer and the like. One of ordinary skill would recognize that
each decoder unit 18 may have more or fewer electrical leads for
carrying out the intended control operation. The LED module 4 may
include a heat resistor 20 disposed between the LEDs 6a-d. The heat
resistor 20 may be energized when defogging or deicing of the dome
8 or other internal components is needed. If desired, one of the
decoder units 18 may be configured to control the heat resistor 20.
Alternatively, a separate electrical conductor connected to a
switch (not shown) may control operation of the heat resistor
20.
[0039] With reference to FIG. 9, in one arrangement, the PCB
assembly at the junctions 5 may include electrical conductors 11a-c
and 13a-b. The conductors may be provided in a two-by-three array
for selectively energizing the intended LED 6a-d within the LED
module 4. More or fewer conductors may be used depending on the
desired configuration. Conductor 11c can be used for providing
power or other signals to the decoder unit 18. The decoder unit 18
may be connected to the electrical conductors 11a-c and 13a-b in a
conventional manner to enable control of LEDs 6a-d.
[0040] FIG. 14 illustrates one possible arrangement of conductors
and an LED module 4 at the junction 5 without a decoder unit
controlling the LED module. In one embodiment, the PCB assembly 2
may be constructed in a multilayered arrangement in which the
different conductive layers include conductors in the X-direction
and the Y-direction, separated by an insulating layer. FIG. 14
shows a two-by-two array of conductors x1, x2 and conductors y1, y2
disposed on different conductive layers for energizing LEDs 6a-d.
In operation, each LED 6a-d may be energized in a number of
different configurations. For example, LED 6a may be energized with
conductor x1 and conductor y1; LED 6b may be illuminated with
conductor x1 and conductor y2. LED 6c can be illuminated with
conductor x2 and conductor y2. LED 6d may be energized by conductor
x2 and conductor y1. Nonetheless, all the conductors x1-2 and y1-2
may be used to illuminate all the LEDs 6a-d for increased
brightness. While LED modules with four LEDs have been shown, a
single LED may be disposed at the junctions and operate with or
without a decoder unit. In this approach, the LEDs 6a-d can be
addressable by the conductor arrangement.
[0041] FIGS. 10-12 illustrate alternative arrangements of the PCB
assembly 2 for providing heat dissipation for cooling the LED
modules. The PCB assembly 2 includes thermodynamic cooling features
and aerodynamic features, such as a plurality of air vents 22. The
vents 22 enable air to pass through the PCB assembly 2 to reduce
wind pressure on the PCB assembly and may assist with heat
dissipation. This vent configuration advantageously enables the PCB
assembly to be implemented in high environments and prevents
excessive wind loading. Additionally the air vents 22 are
configured for removing the heat generated by the LED modules 4 and
other electrical components. The cooling exchange provided by the
vents 22 reduces localized hot spots in the PCB assembly 2.
[0042] As can be seen in FIGS. 1-4 and 10-12, the junctions 5 are
connected by bridges 17 in which the air vents 22 are defined
between the bridge and junctions. The multilayer substrate includes
the bridges 17. The air vents 22 are devoid of material between
four adjacent junctions 5 and bridges 17. As can be seen in the
FIGS. 10-12, the air vents 22 are generally shaped as a square
configuration. Nonetheless, other shapes are possible. The bridges
17 have a width smaller than the diameter of the junctions 5. A
ratio of the width of the bridges to the diameter of the junctions
is less than one. This is one way of controlling the size of the
vents by controlling the width of the bridges 17. Advantageously,
this configuration reduces wind pressure on the PCB assembly 2. In
an exposed environment, the air may flow through the vents 22 for
passive cooling of the LED modules 4 by way of natural
convection.
[0043] In an enclosed arrangement, fluidic cooling of the PCB
assembly 2 can be implemented by providing a cooling fluid of
sufficient velocity and a volume to flow over the LED modules 4 and
through the fluid vents 22. The cooling fluid may flow in a
direction parallel to a plane formed by the X-direction and
Y-direction. Alternatively, the cooling fluid with sufficient
volume and velocity may flow primarily through the air vents 22 by
being directed generally perpendicular of the plane of the PCB
assembly 2. A cooling fluid may be a gas, such as ambient air,
drawn external to the PCB assembly 2 in an enclosed arrangement.
Alternatively, the cooling fluid could be recirculated air after
heat is removed via an air conditioning device (not shown). The
heat is removed from LED modules 4 by convection.
[0044] FIG. 8 shows an alternative PCB assembly 2' with large size
vents 26 to promote additional air passing through PCB assembly and
additional cooling of the LED modules 4. The size of the vents 26
are controlled by the width of the bridges 6' and the length. This
configuration enables more air to pass through the vents 26 for
reducing wind loading and subsequent stress on the structure. PCB
assembly 2' has similar components of PCB assembly 2. PCB assembly
2' may be used with other aspects of heat dissipation and
aerodynamic features of the present invention. As can be seen in
FIG. 8, the size of the vents is many times the size of each LED
module, thus providing a minimal cross-section to wind.
[0045] FIG. 13 shows a section view of the PCB assembly 2 taken
along line 13-13 of FIG. 10. With reference to FIG. 13, the PCB
assembly 2 may be constructed in a multilayered arrangement
comprising a plurality of layers 2a-g. In such an arrangement,
layers 2a, 2c, 2e and 2g may be composed of a dielectric insulator.
A thermal conductive layer 2b may be disposed between the outer
layer 2a and a dielectric insulator layer 2c. A first electrical
conductive layer 2d may be disposed between dielectric insulator
layers 2c and 2e. A second electrical conductive layer 2f may be
disposed between insulator layers 2e and 2g. The substrate may have
more or fewer layers and other arrangements of the layers are
possible. In the embodiments shown in FIG. 10-12, the sidewalls 7
may also be the outer layer 2a of the multilayer substrate. The PCB
assembly 2 may be manufactured using conventional multilayered
conductor techniques. The leads 16 of LEDs 6a may extend through
holes in the dielectric layer 2a, thermal conductive layer 2b, and
dielectric layers 2c, 2e to the conductive layers 2d and 2f. In
another example, each lead 16 may be same length and the holes may
include metal deposits through conventional manufacturing methods
to enable electrical current to flow from the conductor layers to
each lead 16. The thermal conductive layer 2b may the thermally
insolated from the leads 16 and the holes.
[0046] With reference to FIGS. 10, 11 and 13, in one arrangement,
the dielectric outer layer 2a of the PCB assembly 2 may have a
plurality of fluid openings 24 for exposing a thermal conductive
layer 2b for air communication to increase the effective convective
contact area to allow heat dissipation of the LED modules 4. The
openings 24 are devoid of a dielectric material so as to form
pathways in which a flowing cooling fluid, such as air, may contact
the thermal conductive layer 2b to receive heat. In such an
arrangement, the air may enter the opening 24 and the air is
prevented from flow through the PCB by the thermal conductive layer
2b. In FIGS. 10 and 13, the openings 24 may have a circular shape.
Nevertheless, the openings 24 may have other shapes depending on a
desired cooling performance with respect to the convective contact
area. For example, the shapes may be square, rectangular,
triangular, oval, and the like.
[0047] As shown in FIG. 11, the openings 24 may be in the form of
the slots in the dielectric outer layer 2a. The openings 24 may be
disposed on the top surface of the PCB assembly substrate.
Alternatively, the openings 24 may be located on a sidewall 7 in
the vents 22 of the PCB assembly substrate. The sidewall 7
arrangement of the opening 24 in combination with a cooling fluid,
such as air, flowing through the vents 22 provides an incremental
heat transfer advantage by enabling increased fluid exchange with
the thermal conductive layer 2b. The material of the thermal layer
2b may have an appropriate heat transfer coefficient based on the
heat generating characteristics of the LED modules 4. The thermal
conductive layer 2b can be composed of a number of alternative
materials, including a copper, aluminum, or a mixture of metal
particulates suspended in a plastic material. The thermal
coefficient of thermal expansion of the conductive layer and
dielectric layers would be matched to take into account any thermal
induced mechanical stress. If desired, small holes may extend all
the way through the substrate in the bridge 17 so air can pass
through the bridge. The small holes may be placed proximate to the
LED modules to close proximity to the location of heat generation.
In this way, there is the possibility of obtaining improved heat
dissipation.
[0048] With reference to FIG. 13, to transfer heat from the LED
module 4, the thermal conductive layer 2b may be physically
connected to the base member 10, in particular to the protrusions
12 of the LED module 4. In one configuration, the base member 10
may serve as a heat sink with respect to the LEDs 6a-d. The thermal
conductive layer 2b may be a lower temperature than the LED module
4. Thus, a resultant thermal temperature differential enables the
heat generated by the LED 6a-d to be transferred to the base member
10 and to the thermal conductive layer 2b. To enhance cooling of
the PCB assembly 2, in one embodiment, a thermoelectric cooling
module (not shown) may be used to lower the temperature of the
thermal conductive layer 2b. This creates an enhanced heat sink
performance for the thermal layer. The thermoelectric cooling
module may be powered with the conductors from layers 2d and
2f.
[0049] FIG. 16 illustrates a section view of an alternative
multilayer substrate 50 with an LED 32. LED 32 includes a cathode
lead 52 and an anode lead 54 for receiving electrical power. The
lead 52 of LED 32 may be connected to trace layer 50b. The lead 54
of LED 32 may extend to trace layer 50d. To maximize the heat
dissipation performance, the thermally conductive layer(s) 50a and
50c may be disposed in close proximity to the trace/layer 50b which
is thermally and electrically connected to the cathode lead 52 of
the LED. As shown in FIG. 16, either side of the trace layer 50b
can be sandwiched by the thermal layer(s) 50a and 50c to provide
maximum thermal dissipation and/or heat sinking. Thermal layer 50c
may be disposed between the trace layer 50b and layer 50d. Hence, a
single thermal conductive layer may simultaneously provide heat
transfer benefits for both trace layers. This configuration may
also reduce the thickness of the substrate 50.
[0050] While a single LED is shown, the inventive aspects can be
practiced with multiple LEDs or LED modules. Multilayer substrate
50 may be used with PCB assembly 2 shown in FIGS. 1-4 and the air
vents 22 for maximum heat conduction. The thermal conductive layer
50a and 50c may be composed of various materials which provide
thermal conduction yet high electrical resistance, including
polymeric, polymeric blends, or carbon fibers.
[0051] FIG. 12 illustrates an alternative heat dissipation
arrangement including an outer exposed layer 30 which may serve
both electrical and thermal conductive functions. In this
arrangement, the convective contact area is increased for cooling
the LED module or LEDs in the cooling configuration. The layer 30
may serve as an electrical conductor for the LED module or
LEDs.
[0052] FIG. 15 illustrates a section view of an alternative
multilayer substrate 34 with an LED 32. Multilayer substrate 34
includes an exposed upper layer 34a that serves as both an
electrical conductor and a thermal conductor for heat dissipation.
Upper layer 34a may include one or more conductors in the
X-direction. A bottom electrical conductive layer 34c may include
one or more conductors in the Y-direction. A dielectric insulating
layer 34b may be disposed between the layer 34a and layer 34c. LED
32 includes two lead 36, 38 for receiving electrical power. The
lead 36 of LED 32 may be connected to upper layer 34a. The lead 38
of LED 32 may extend through holes in layer 34a, and dielectric
layer 34b to the conductive layer 34c. While a single LED is shown,
the inventive aspects can be practiced with multiple LEDs or LED
modules. Multilayer substrate 34 may be used with PCB assembly 2
shown in FIGS. 1-4 and the heat dissipation vents 22. In this
embodiment, electrically and thermally conductive layer 34a assists
in dissipating heat from LED 32.
[0053] In another variation, layer 34a may comprise a thermally
conductive layer that has poor electrical conducting qualities,
thus helping to dissipate heat while acting as an electrical
insulator. Layer 34b could then be used as the electrical path to
LED 32, and another layer 34d (not shown) would act as the other
electrical conductor. In this variation, LED leads 36 and 38 would
be connected to layers 34b and 34d (not shown) for electrical
connectivity.
[0054] FIG. 17 illustrates a partial schematic diagram of an
alternative PCB assembly 60 with a two-sided aerodynamic
configuration which provides a benefit of reducing wind pressure.
In this configuration, the substrate 62 has a front side 64 and
rear side 66. The LED module 32 may mounted on the front side 64
and the LED module 32 may include a dome 8. The rear side of the
PCB assembly 60 may include an aerodynamic member 68 for reducing
wind pressure. The PCB assembly 60 includes air vents (not shown)
for enabling air to pass through the PCB. Air flowing towards the
LED module 32 of dome 8 can reduce air pressure, and air flowing in
an opposite direction also has reduced resistance with respect to
the structure. The aerodynamic member may comprise various shapes
such as a hemispherical shape or a nose cone shape.
[0055] Other configurations of the PCB assembly are possible to
increasing heat dissipation. In one arrangement shown in FIG. 18,
the bridge 17 may include a plurality of roughness members 70 on
the surface of the multilayer substrate. The roughness members 70
protrude from the surface of the substrate. The members 70 can have
a variety of shapes, such as hemispherical and the like. These
roughness members 70 may be provided to promote small air
turbulence to reduce the boundary layer for reducing the insulating
effects of the air and promote increased heat transfer from the
thermal layer to the air. Thus, in the embodiments of exposing the
thermal layer to the air, roughness members 70 may increase the
interaction of the air with the thermal layer to improved passive
cooling. One of ordinary skill in the air may embodiment
computational fluid mechanics and the like for specific dimensional
characteristics.
[0056] While the present invention has been described with
reference to preferred embodiments, it will be understood by those
of ordinary skill in the art that various changes may be made and
equivalents may be substituted for elements without departing from
the scope of the invention. In addition, many modifications may be
made to adapt a particular feature or material to the teachings of
the invention without departing from the scope thereof. Therefore,
it is intended that the invention not be limited to the particular
embodiments disclosed, but that the invention will include all
embodiments falling within the scope of the appended claims.
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