U.S. patent application number 14/254142 was filed with the patent office on 2014-08-14 for bendable circuit board for led mounting and interconnection.
This patent application is currently assigned to E I DU PONT DE NEMOURS AND COMPANY. The applicant listed for this patent is E I DU PONT DE NEMOURS AND COMPANY. Invention is credited to Daniel I. Amey, Deborah R. Gravely, Michael J. Green, Steven H. White.
Application Number | 20140226347 14/254142 |
Document ID | / |
Family ID | 40394177 |
Filed Date | 2014-08-14 |
United States Patent
Application |
20140226347 |
Kind Code |
A1 |
Amey; Daniel I. ; et
al. |
August 14, 2014 |
BENDABLE CIRCUIT BOARD FOR LED MOUNTING AND INTERCONNECTION
Abstract
This invention is directed to bendable circuit substrate
structures useful for LED mounting and interconnection.
Inventors: |
Amey; Daniel I.; (Durham,
NC) ; Gravely; Deborah R.; (Martinsville, VA)
; Green; Michael J.; (Cary, NC) ; White; Steven
H.; (Chapel Hill, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
E I DU PONT DE NEMOURS AND COMPANY |
Wilmington |
DE |
US |
|
|
Assignee: |
E I DU PONT DE NEMOURS AND
COMPANY
Wilmington
DE
|
Family ID: |
40394177 |
Appl. No.: |
14/254142 |
Filed: |
April 16, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13965778 |
Aug 13, 2013 |
8707551 |
|
|
14254142 |
|
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13269148 |
Oct 7, 2011 |
|
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13965778 |
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12744685 |
May 26, 2010 |
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PCT/US08/85292 |
Dec 3, 2008 |
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13269148 |
|
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61005222 |
Dec 4, 2007 |
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Current U.S.
Class: |
362/382 ;
174/254; 72/379.2 |
Current CPC
Class: |
H05K 1/189 20130101;
Y10T 428/24975 20150115; H05K 2201/10106 20130101; H05K 2201/0209
20130101; H05K 2203/0315 20130101; H05K 3/22 20130101; Y10T
428/31678 20150401; H05K 3/386 20130101; F21V 21/00 20130101; Y10T
29/49144 20150115; H05K 2203/302 20130101; H05K 2201/0154 20130101;
H05K 1/056 20130101; Y10T 29/49147 20150115; Y10T 428/31681
20150401; Y10T 29/49126 20150115; Y10T 29/49117 20150115; H05K
1/0271 20130101; Y10T 29/49002 20150115; H05K 1/028 20130101; Y10T
428/12569 20150115; Y10T 428/24 20150115; Y10T 29/49124
20150115 |
Class at
Publication: |
362/382 ;
174/254; 72/379.2 |
International
Class: |
F21V 21/00 20060101
F21V021/00; H05K 1/02 20060101 H05K001/02 |
Claims
1. A bendable laminated structure for mounting light emitting
diodes ("LED") comprising, a. an aluminum metal layer between about
0.2 millimeters and 2 millimeters in thickness; b. a polyimide
layer directly contacting one side of the aluminum metal layer; and
c. a copper foil layer directly another side of the polyimide
layer; wherein the laminated structure has a thickness between
about 0.2 millimeters to about 3 millimeters and increases in
electrical resistance by less than 10% after being bent at an angle
of 90.degree. or greater.
2. The structure of claim 1 wherein the copper layer is about 35 um
thick, the polyimide layer is at about 0.12 millimeters thick and
the aluminum layer is about 0.2 millimeters to 0.247 millimeters
thick.
3. The structure of claim 1 wherein the aluminum metal layer is
about 0.4 mm to about 2 mm in thickness.
4. The structure of claim 1, where the copper layer is a
circuitized layer.
5. The structure of claim 1 wherein the aluminum is anodized.
6. The structure of claim 1 wherein the aluminum is treated with a
chemical conversion coating.
7. The structure of claim 1 wherein the aluminum is aluminum Alloy
5005.
8. A method of manufacturing a laminated structure for mounting
light emitting diodes ("LED") to a 90.degree. or greater configured
angle, comprising: a. providing a bendable a laminate circuit
structure, the bendable laminate circuit structure having at least
the following laminated layers: i. an aluminum metal layer of about
0.2 mm to about 2 mm in thickness; ii. a polyimide composite layer
having a first surface directly contacting the first surface of the
aluminum metal layer; and iii. a copper foil layer directly
contacting a second surface of the polyimide composite layer; and
b. bending the laminated layers 90.degree. or more, such that after
bending the laminated layers the bendable circuit structure for
mounting LED mounting has an increase in electrical resistance of
less than 10%.
9. The method of claim 8 wherein the providing step include
providing a laminate wherein the copper layer is about 35 um thick,
the polyimide layer is about 12 um thick and the aluminum layer is
about 200 um to 247 um thick.
10. The laminate of claim 8 wherein the providing step includes
providing an aluminum metal layer of about 0.4 mm to about 2 mm in
thickness.
11. The method of claim 8, wherein the bendable laminate structure
has a thickness to about 3 millimeters.
12. The method of claim 8, where the copper layer of the laminated
layers is a circuitized layer.
13. A bent, laminated circuit, bent at 90.degree. or greater to
form a reconfigured structure, comprising, a. an aluminum metal
layer between about 0.3 mm and 2 mm um in thickness; b. a polyimide
layer directly contacting one side of the aluminum metal layer; and
c. a copper foil layer directly another side of the polyimide
layer; wherein the structure has a thickness up to about 3
millimeters, and the reconfigured structure has an increased
electrical resistance of less than 10% as a result of being bent an
angle of 90.degree. or greater.
14. The structure of claim 13, where the copper layer is a
circuitized layer.
15. The structure of claim 13 wherein the aluminum is anodized.
16. The structure of claim 13 wherein the aluminum is aluminum
Alloy 5005.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/269,148, filed Oct. 7, 2011, which is a
continuation of U.S. patent application Ser. No. 12/744,685, filed
May 26, 2010, which is a 35 U.S.C, .sctn.371 National Stage
Application of International PCT/US08/85292, which claims Priority
to Provisional Application 61/005,222, filed Dec. 4, 2007.
FIELD OF THE INVENTION
[0002] This invention is directed to a flexible substrate structure
used for LED (light emitting diode) mounting and
Interconnection.
TECHNICAL BACKGROUND OF THE INVENTION
[0003] Insulated metal substrates are being used for the mounting
and interconnection of light emitting diodes (LEDs) in applications
such as display back lighting, automotive lighting and general
commercial and consumer lighting uses. The substrates currently
being used are generally rigid and are not able to be deformed and
bent without degradation or damage to their mechanical, electrical
and thermal properties. It is desirable to be able to form or bend
such substrate materials to make angles, curves or bends, while
maintaining mechanical and thermal integrity and without causing
degradation of the substrate or of its electrical properties.
[0004] Multi-functional electronic substrate materials of various
kinds are known in the art. Some of the layers of these substrates
can be made of various polymer materials such as polyimide
(hereinafter referred to as "PI"). In general, these are rigid
structures with little flexibility, unless the structure is
grooved.
[0005] U.S. 2007/0076381 A1, for example, describes a flexible heat
spreader circuit board with a heat sink. The flexibility of its
circuit board results froth a pattern of grooves that make an upper
surface and a lower surface flexible when the substrate is
bent.
[0006] Aluminum substrates are known for use in visible LED
Circuits. Canadian Electronics Magazine e-magazine, for example as
shown in an article titled "Aluminum Substrates Make light work of
visible LED Circuits" by Tom Morris, dated Sep. 18, 2007.
Economical solderable polymer thick film conductors can be screen
printed directly onto such substrates, without degradation. The
article mentions that aluminum alloy substrates can be extruded,
die cast and made in special shapes. The thermally conductive
aluminum alloy material enables design engineers to mount high
power LED components directly to it. However, no mention is made of
any flexibility of such alloy substrates.
[0007] In an article titled "Poor fixtures threaten to jeopardize
the illumination potential of LEDs" by Richard Stevenson, Compound
Semiconductor, June 2007, the author points out that the low
efficiency of many fixtures in the industry results from lack of
skills relating to working on the design aspects of these fixtures,
by the workforce of many companies, who work with the electrical
systems used in powering LEDs. These techniques are needed for
thermal management and optical design.
[0008] As applications expand requiring more complex mechanical
configurations and circuitry becomes thinner and more complicated,
it is desirable for the substrates to be shapeable without any
resulting degradation of the substrate surface characteristics or
without interfering with their thermal or electrical properties. It
is also desirable for chosen substrates to be cost effective, be
easy to handle and be able to be used in fixtures allowing the best
use of the light from an LED. The laminate described in the present
patent application is useful in such fixtures as it can be shaped
for improved optical properties without any degradation of its
electrical properties and with its thermal properties maintained.
The ability to bend a laminated structure without degrading the
electrical circuitry allows the configuring of LED's in a "3D"
format. Such structures are not limited to a planar format. Having
this bendable ability provides the device designer with more
options to tailor and optimize the device design. Overcoming the
limitations in LED mounting and LED structure and fixtures imposed
by rigid substrate materials and interconnection materials allows
the designer to customize and optimize the mechanical features
found in Solid State lighting components.
[0009] The present flexible structure is expected to increase
overall optical electrical efficiency from 30% to 40% of the range
currently seen in LED structures and to optimize the configuration
manually by allowing the bending at the most efficient
configuration to concentrate and disperse LED light.
SUMMARY OF THE INVENTION
[0010] The present invention concerns a laminate comprising, on a
substrate the following layers: [0011] (a) a copper or aluminum
metal layer; [0012] (b) a polyimide or adhesive layer, the metal
layer being adjacent to the polyimide or adhesive layer [0013] (c)
copper foil layer and [0014] (d) liquid or film solder mask
layer.
[0015] The laminate may be a thin polymer based copper clad filled
polyimide (PI), for example a CooLam.TM. thermal laminate such as
LC (Alumina Filled PI) and LX (Alumina Filled PI), used in
conjunction with an aluminum alloy composition substrate. The
laminate may also be an anodized aluminum CooLam.TM. thermal
laminate, such as LU (Anodized Aluminum and with adhesive). Such
laminates must be designed to be used in a composition of the
proper thickness for LED applications. Use of such laminates
creates a versatile and bendable structure for ease of use in LED
packaging.
[0016] As pointed out above, a suitable family of materials useful
in this invention is the CooLam.TM. thermal laminates. Examples are
embodiments such as LC (Alumina Filled PI), LU (Anodized Aluminum
with adhesive) and LX (Alumina Filled PI). A CooLam.TM. structure
consists of a metal, optionally an adhesive (only in the LU
(Anodized Aluminum with adhesive) embodiment), polyimide (PI),
copper foil and a solder mask. See drawings FIGS. 3A and 3B (key).
LU products may also be alumina filled.
BRIEF DESCRIPTION OF THE DRAWING
[0017] FIG. 1 shows a typical laminate substrate, with bend
locations 6, 7 and 8.
[0018] FIG. 2 shows the detail of test lines 6. Two traces that
were measured are labeled 9 and 10.
[0019] FIG. 3(A) shows the stacking arrangements of CooLam.TM.
Laminates.
[0020] FIG. 3(B) serves as a "key" to the drawing in FIG. 3(A). In
FIG. 3(B) the 1/2 ounce to 4 ounces Cu, in metric units, is "14.79
milliliters to 118.29 milliliters".
DETAILED DESCRIPTION OF THE INVENTION
[0021] Referring to FIGS. 3(A) and 3(B), the term "laminate" herein
is referred to as the metal (1) and the polyimide (3), and adhesive
(2) where adhesive is present, plus the copper foil (4). The term
"substrate" refers to the metal itself (1). The finished product
with patterned copper foil and solder mask (5) is called a "Metal
Core Printed Circuit Board" or an "Insulated Metal Substrate"
(IMS).
[0022] In one embodiment, the copper is at 18 um, the dielectric is
at 6 um and aluminum is at 100 um. In another embodiment the copper
is at 35 um, dielectric is at 12 um and the aluminum is at a
thickness selected from the following group of thicknesses: 200 um
and 247 um.
[0023] The composite films of the present invention are generally
derived from a multi-layer structure having one or more polyimide
composite layers. These polyimide composites and layers can have
thermal conductivity, electrical conductivity, electrical
resistivity, electrical capacitance and other desirable properties.
They can also be layered in various ways to create other sought
after properties. An example of such a layering plan for a coating
on a substrate is described in U.S. Pat. No. 7,100,814, which is
incorporated herein by reference. Some of the layered structures
known in the art lack flexibility which results in cracking and
breakage upon their use. The laminate thickness is from about 125
microns to about 3 millimeters. Allowing substrate flexibility
results in cost reduction, the need for fewer pieces, need for less
handling and greater ease of installation, along with improved
appearance and the ability to create custom shapes and more
efficient configurations to concentrate or distribute light,
offering improved illumination and appearance characteristics.
EXAMPLES
Tests To Determinate Interconnection Integrity of the Present
Laminate
[0024] Tests to determine interconnection integrity of CooLam.TM.
laminate under bending stress were performed on substrates
fabricated with 17 micron thick CooLam.TM. thermal laminate and 2
mm thick Aluminum Alloy 5005 using a LCD Backlight Unit circuit
design. The purpose of this testing was to determine the
feasibility of offering this type of construction for applications
in LED lighting.
[0025] The overall sample size was 17 mm.times.423 mm
(5/8''.times.17'') and consists of 6 identical segments is shown in
FIG. 1.
[0026] Three locations on each of six pieces were tested as shown
in FIG. 1. The resistance of two 11.8 mil 1.4 mil thick traces,
shown as 9 and 10 in FIG. 2, in each location was measured before
and after bending. The bend point centerline on each segment was
positioned on the centerline of a 11/8'' diameter mandrel and bent
by hand to an approximate 90 degree bend. The laminate/conductor
was on the outside of the bend putting the material in tension. The
actual bend profile for each location tested was traced or compared
to prior sample traces and entered in a notebook with the test
data. The following Table 1 tabulates the resistance test results
for the configurations. Visual examination at the bend point
evidenced no cracking or crazing of the solder mask. Resistance
measurements were performed using an Electro Scientific Industries
1700 series Micro-Ohmmeter system using the 20 milliohm range
(resolution of 1 micro Ohm).
[0027] The average change in resistance of all the circuit lines
was 1.55 milliohms with a maximum of 3 milliohms and a minimum of
0.8 milliohms. This testing indicates that the CooLam.TM. material
used in a metal-backed structure has the potential to be bent to 90
degrees or greater angles with reliable interconnections.
TABLE-US-00001 TABLE 1 RESIS- RESIS- RESIS- TANCE TANCE TANCE LO-
BEFORE AFTER CHANGE- SAM- CA- BENDING- BENDING- MILLI- PLE TION
TRACE MILLIOHMS MILLIOHMS OHMS 1 1 1 17.3 18.2 0.9 1 1 2 17 17.9
0.9 1 2 1 17 18.5 1.5 1 2 2 17.6 18.4 0.8 1 3 1 17.4 18.5 1.1 1 3 2
17.8 18.6 0.8 2 1 1 17.3 19.3 2 2 1 2 17.2 19 1.8 2 2 1 17.7 19.4
1.7 2 2 2 18.1 19.2 1.1 2 3 1 17.8 18.6 0.8 2 3 2 17.6 19.7 2.1 3 1
1 17.8 19.6 1.8 3 1 2 16.5 19.5 3 3 2 1 17.9 19.6 1.7 3 2 2 17.6
19.3 1.7 3 3 1 18.2 19.3 1.1 3 3 2 17.8 19.4 1.6 4 1 1 18.5 19.5 1
4 1 2 18 19.9 1.9 4 2 1 18.2 19.8 1.6 4 2 2 17.9 19.7 1.8 4 3 1
17.9 19.7 1.8 4 3 2 18 19.6 1.6 5 1 1 17.3 19.2 1.9 5 1 2 17.9 19.8
1.9 5 2 1 17.6 19.3 1.7 5 2 2 18 19.2 1.2 5 3 1 17.7 19.8 2.1 5 3 2
17.9 19.4 1.5 6 1 1 17.9 19.2 1.3 6 1 2 17.9 19.8 1.9 6 2 1 18.3
19.6 1.3 6 2 2 18.1 19.7 1.6 6 3 1 17.9 19.5 1.6 6 3 2 18.3 19.9
1.6
* * * * *