U.S. patent application number 14/502169 was filed with the patent office on 2015-01-15 for three dimensional light emitting diode systems, and compositions and methods relating thereto.
The applicant listed for this patent is E I DU PONT DE NEMOURS AND COMPANY. Invention is credited to KURT DOUGLAS ROBERTS.
Application Number | 20150016122 14/502169 |
Document ID | / |
Family ID | 46827775 |
Filed Date | 2015-01-15 |
United States Patent
Application |
20150016122 |
Kind Code |
A1 |
ROBERTS; KURT DOUGLAS |
January 15, 2015 |
THREE DIMENSIONAL LIGHT EMITTING DIODE SYSTEMS, AND COMPOSITIONS
AND METHODS RELATING THERETO
Abstract
A flexible layered structure is disclosed having a flexible top
conductive layer, a flexible bottom heat sink layer and a flexible
dielectric middle layer. The combination has a longitudinal axis
and a plurality of defined positions spaced along the longitudinal
axis. The defined positions can be used for aligning a circuit
and/or for the placement of LED lights. The flexible layered
structure can be easily bent to form a LED substrate for shining
light in more than one direction while efficiently removing heat
arising from the LEDs.
Inventors: |
ROBERTS; KURT DOUGLAS;
(Raleigh, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
E I DU PONT DE NEMOURS AND COMPANY |
Wilmington |
DE |
US |
|
|
Family ID: |
46827775 |
Appl. No.: |
14/502169 |
Filed: |
September 30, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14059570 |
Oct 22, 2013 |
8860048 |
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14502169 |
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13326623 |
Dec 15, 2011 |
8637880 |
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14059570 |
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Current U.S.
Class: |
362/373 |
Current CPC
Class: |
F21V 29/70 20150115;
F21S 4/24 20160101; H05K 1/0278 20130101; F21K 9/23 20160801; F21K
9/27 20160801; H01L 2924/0002 20130101; H05K 1/189 20130101; H01L
25/0753 20130101; F21V 29/74 20150115; H05K 2201/10106 20130101;
H05K 3/0061 20130101; F21Y 2115/10 20160801; H01L 2924/0002
20130101; H01L 33/642 20130101; F21Y 2103/10 20160801; H05K
2201/09745 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
362/373 |
International
Class: |
F21V 29/00 20060101
F21V029/00; F21K 99/00 20060101 F21K099/00 |
Claims
1. An LED lighting assembly comprising: i. a flexible top
conductive layer comprising a first conductive metal, the flexible
top conductive layer having a thickness from 4 to 100 microns; ii.
a flexible bottom heat sink layer comprising a second conductive
metal and the flexible bottom heat sink layer having a thickness of
at least 50 microns; iii. a flexible dielectric middle layer
comprising a polymer, the flexible dielectric middle layer having a
thickness from 4 to 100 microns and providing electrical insulation
between the flexible top conductive layer and the flexible bottom
heat sink layer; the first conductive metal of the flexible top
conductive layer being the same or different from the second
conductive metal of the flexible bottom heat sink layer; said LED
lighting assembly having a longitudinal axis and a plurality of
defined positions spaced along the longitudinal axis, and being
bent at least 10 degrees proximate at least one of the plurality of
defined positions spaced along the longitudinal axis or being
twisted relative to the longitudinal axis; and wherein at least a
portion of the plurality of defined positions comprise an LED and
wherein the LED is in electrical communication with a circuit.
2. The LED lighting assembly in accordance with claim 1 having a
light bulb replacement configuration sufficient to be a replacement
for one or more of the following: A-lamp bulbs, PAR-lamp bulbs,
R-lamp bulbs, MR16-lamp bulbs, candelabra lamp bulbs and linear
fluorescent bulbs.
3. The LED lighting assembly in accordance with claim 1 having a
configuration sufficient to provide one or more of the following
types of lights: cove lights; residential overhead lights; linear
lights; rope lights; accent lights; projector lights; stage bar
lights; par lamp lights; color changer lights; display case lights;
undercabinet lights; backdrop lights; refrigerated display case
lights; hazardous lights; industrial fixture lights; functional
office lights; down lights; recessed lights; roadway lights; canopy
lights; area lights; pole top lights; solar flood lights; lantern
lights; decorative suspended lights; task lights; flash light;
headlamps; work lights; and exit sign lights.
4. The LED lighting assembly in accordance with claim 1, wherein
the LED lighting assembly is conformed to at least a portion of a
secondary heat sink and bonded to the secondary heat sink by at
least a portion of a heat sink adhesive layer.
5. The LED lighting assembly in accordance with claim 1, wherein at
least 50 weight percent of the flexible dielectric middle layer is
a polyimide derived from at least 30 mole percent aromatic
dianhydride based upon total dianhydride content of the polyimide
and at least 30 mole percent aromatic diamine based upon total
diamine content of the polyimide.
6. The LED lighting assembly in accordance with claim 1 wherein the
flexible dielectric middle layer comprises 1 to 50 weight percent
thermally conductive filler, the thermally conductive filler
comprising one or more members of the group consisting of carbides,
nitrides, borides and oxide.
Description
FIELD OF THE INVENTION
[0001] The field of the invention is light emitting diode ("LED")
structures for three dimensional lighting applications.
BACKGROUND OF THE INVENTION
[0002] U.S. 2009/0226656 A1 is directed to a multi-layered
structure for use with a high power, light emitting diode system.
The structure is at least semi-flexible and is exemplified as
comprising an FR4 epoxy based material that may also include a
layer of fiberglass. Typically these structures are not capable of
maintaining the bend or keeping the position the structure is bent
or twisted to form.
[0003] Automotive backlights have been known to use LEDs, but are;
very low power, have low heat dissipation, operate at much lower
voltages and have shorter in use life than general lighting
fixtures and replacement bulbs. Therefore there is a need for
higher power LED lighting systems that have much higher heat
dissipation, tested at much higher voltages required for safety
recognition (as much as 250X the voltage required for automotive
lighting), with expected in use life of over 25,000 hours of
continuous usage and LED lighting applications requiring improved
quality of light with design freedom and design for assembly or
manufacture.
SUMMARY OF THE INVENTION
[0004] The present disclosure is directed to an LED lighting
assembly. The LED lighting assembly comprises a flexible layered
structure having a flexible top conductive layer. At least a
portion of the flexible top conductive layer is a metal. The
flexible top conductive layer has a thickness from 4, 6, 8, 10, 12,
15, or 20 microns to 50, 75, 100, 200, or 300 microns. The flexible
layered structure also comprises a flexible bottom heat sink layer
having a thickness of at least 10, 20, 25, 30, 40, 50, 75, or 100
microns. In some embodiments, the flexible bottom heat sink layer
has a thickness up to and including 4000 microns. In some
embodiments, the flexible bottom heat sink layer has a thickness
between and including any two of the following: 10, 100, 500, 1000,
2000, 3000 and 4000 microns. At least a portion of the flexible
bottom heat sink layer is a metal which can be the same or
different from the metal of the flexible top conductive layer. The
flexible layered structure of the present disclosure also comprises
a flexible dielectric middle layer comprising a polymer. The
flexible dielectric middle layer has a thickness from 1 to 100
microns and provides electrical insulation between the flexible top
conductive layer and the flexible bottom heat sink layer.
[0005] The flexible layered structure having a longitudinal axis
and a plurality of defined positions spaced along the longitudinal
axis. The defined positions can be used for aligning a circuit or
for the placement of LED lights. In some embodiments, the defined
positions can also have a notch, to aid in bending the flexible
layered structure. A notch is intended to mean any indentation into
either the flexible top conductive layer or flexible bottom heat
sink layer, whether by cutting, pressing, abrading, etching or
otherwise. The combined flexible top conductive layer, middle
dielectric layer and flexible bottom heat sink layer combine to
form a structure that is bent at least 10, 20, 30, 40, 45, 60, 90,
120 or 180 degrees proximate to at least one of the defined
positions spaced along the longitudinal axis and the combination is
also twistable relative to the longitudinal axis. Twistable is
intended to mean a torsion force of about 10 Newtons can deflect
the flexible layered structure at least 5, 10, 15, 20, 25, or 30
degrees when the distance of the flexible layered structure
experiencing the torsion force is about 25 centimeters. At least a
portion of the plurality of defined positions comprise an LED and
the LED is in electrical communication with a circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1A is a perspective view of a flexible layered
structure for use with high power light emitting diode systems.
[0007] FIG. 1B is a perspective view of a flexible layered
structure conforming to the structure of a secondary heat sink.
[0008] FIG. 2 is a cross-section view of an alternative embodiment
of the flexible layered structure of the present disclosure.
[0009] FIG. 3 is a side view of a reel onto which the flexible
layered structure shown in FIG. 1 could be wound.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Definitions
[0010] "Flexible" is intended to mean bendable or twistable to a
desire position or formation, after which maintains the position or
formation. After bending or twisting, the resulting three
dimensional structures may be rigid.
[0011] "Film" is intended to mean a free-standing film or a
(self-supporting or non self-supporting) coating and includes
multiple layers. The term "film" is used interchangeably with the
term "layer" or "multilayer" and refers to covering a desired
area.
[0012] "Layer" is intended to include circuitized layers, such as
where a metal layer is patterned by photolithography to produce a
pattern of metal traces or circuits.
[0013] "Dianhydride" as used herein is intended to include
precursors or derivatives thereof, which may not technically be a
dianhydride but would nevertheless react with a diamine to form a
polyamic acid which could in turn be converted into a
polyimide.
[0014] Similarly, "diamine" as used herein is intended to include
precursors or derivatives thereof, which may not technically be a
diamine but would nevertheless react with a dianhydride to form a
polyamic acid which could in turn be converted into a
polyimide.
[0015] An "aromatic diamine" is intended to mean a diamine having
at least one aromatic ring, either alone (i.e., a substituted or
unsubstituted, functionalized or unfunctionalized benzene or
similar-type aromatic ring) or connected to another (aromatic or
aliphatic) ring, and such an amine is to be deemed aromatic,
regardless of any non-aromatic moieties that might also be a
component of the diamine. Hence, an aromatic diamine backbone chain
segment is intended to mean at least one aromatic moiety between
two adjacent imide linkages.
[0016] "Polyamic acid" as used herein is intended to include any
polyimide precursor material derived from a combination of
dianhydride and diamine monomers or functional equivalents thereof
and capable of conversion to a polyimide.
[0017] "Sub-micron" is intended to describe particles having (as a
numerical average) at least one dimension that is less than a
micron.
[0018] "Chemical conversion" or "chemically converted" as used
herein denotes the use of a catalyst (accelerator) or dehydrating
agent (or both) to convert the polyamic acid to polyimide and is
intended to include a partially chemically converted polyimide
which is then dried at elevated temperatures to a solids level
greater than 98%.
[0019] In describing certain polymers it should be understood that
sometimes applicants are referring to the polymers by the monomers
used to make them or the amounts of the monomers used to make them.
While such a description may not include the specific nomenclature
used to describe the final polymer or may not contain
product-by-process terminology, any such reference to monomers and
amounts should be interpreted to mean that the polymer is made from
those monomers, unless the context indicates or implies
otherwise.
[0020] As used herein, the terms "comprises," "comprising,"
"includes," "including," "has," "having" or any other variation
thereof, are intended to cover a non-exclusive inclusion. For
example, a method, process, article, or apparatus that comprises a
list of elements is not necessarily limited to only those elements
but may include other elements not expressly listed or inherent to
such method, process, article, or apparatus. Further, unless
expressly stated to the contrary, "or" refers to an inclusive or
and not to an exclusive or. For example, a condition A or B is
satisfied by any one of the following: A is true (or present) and B
is false (or not present), A is false (or not present) and B is
true (or present), and both A and B are true (or present).
[0021] Also, articles "a" or "an" are employed to describe elements
and components of the invention. This is done merely for
convenience and to give a general sense of the invention. This
description should be read to include one or at least one and the
singular also includes the plural unless it is obvious that it is
meant otherwise.
Overview
[0022] The present disclosure is directed to a flexible layered
structure adapted for use as part of a high power (e.g., greater
than 0.25, 0.5, 1, 2, 3, 4, 5, 8 10, 15, 20 or 25 watts per LED)
light emitting diode system. The flexible layered structure
comprises a flexible top conductive layer, a flexible dielectric
middle layer and a flexible bottom heat sink layer. Optionally
between any of these three layers is an adhesive layer having a
thickness from 1 to 55 microns. Optionally, the flexible dielectric
middle layer comprises thermally conductive filler from the group
consisting of carbides, nitrides, borides and oxides. Optionally, a
heat sink adhesive layer is applied to the flexible bottom heat
sink layer with a release liner on the opposite side; such that,
the release liner can be removed and the flexible layered structure
bonded to a housing, secondary heat sink or other structure.
[0023] The flexible top conductive layer has a thickness from 4, 6,
8, 10, 12, 15, or 20 microns to 50, 75, 100, 200, or 300 microns
and comprises a metal. The flexible top conductive layer is
thermally and electrically conductive. The flexible bottom heat
sink layer has a thickness of at least 10, 20, 25, 30, 40, 50, 75
or 100 microns. In some embodiments, the flexible bottom heat sink
layer has a thickness up to and including 4000 microns. In some
embodiments, the flexible bottom heat sink layer has a thickness
between and including any two of the following: 10, 100, 500, 1000,
2000, 3000 and 4000 microns. In some embodiments, the flexible
bottom heat sink layer comprises a metal. The metal of the flexible
top conductive layer can be the same or different from the metal of
the flexible bottom heat sink layer. In some embodiments, the
flexible dielectric middle layer has a thickness from 1 to 100
microns. In some embodiments, the flexible dielectric middle layer
has a thickness between and including any two of the following: 1,
5, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 microns. In some
embodiments, the flexible dielectric middle layer is from about 4
to about 100 microns in thickness and comprises a mechanically
strong, heat resistant polymer, such as a polyester (such as
polyethylene terephthalate or polybutylene terephthalate),
fluropolymer, acrylonitrile butadiene styrene ("ABS"),
polycarbonates ("PC"), polyamides ("PA"), polyphenylene oxide
("PPO"), polysulphone ("PSU"), polyetherketone ("PEK"),
polyetheretherketone ("PEEK"), polyimides ("PI"), polyphenylene
sulfide ("PPS"), polyoxymethylene plastic ("POM") , polyethylene
naphthalate ("PEN"), or the like.
[0024] The flexible top conductive layer, the flexible dielectric
middle layer, and the flexible bottom heat sink layer form a
flexible layered structure having a longitudinal axis and a
plurality of LED receptacles on the top. The LED receptacles are
the areas the LED is electrically attached. The LED receptacles are
ultimately filled with LED devices and powered at least in part by
the flexible top conductive layer. In some embodiments, the
flexible top conductive layer comprises at least one LED connected
to at least one surface mount technology electrical component by an
electrical circuit.
[0025] The flexible elongate member is bendable laterally proximate
the plurality of LED receptacles spaced along the longitudinal axis
and the flexible elongated member is twistable relative to its
longitudinal axis. The flexible elongated member can be bent and/or
twisted so at least two of the LED lights are directed to and shine
in different directions. In one embodiment, the twisted and/or bent
LED configuration is incorporated into a housing adapted either as
a lighting system itself or as a replacement bulb for a lighting
system. Optionally, the heat sink layer can be partially or wholly
bonded to an additional heat sink material in one embodiment, a
flexible layered structure (sometimes also referred to as a
"flexible member") for use with high power light emitting diode
systems. In one embodiment, FIG. 1A illustrates a flexible layered
structure 100. The flexible layered structure 100 comprises a
flexible dielectric middle layer 110 sandwiched between a flexible
top conductive layer 101 and a flexible bottom heat sink layer 112.
The flexible top conductive layer 101 comprises a first conductive
metal and the flexible bottom heat sink layer 112 comprises a
second conductive metal. The first conductive metal of the flexible
top conductive layer 101 being the same or different from the
second conductive metal of the flexible bottom heat sink layer 112.
In some embodiments, the first conductive metal of the flexible top
conductive layer 101 and the second conductive metal of the
flexible bottom heat sink layer 112 each comprise one or more
metals or metal alloys. The flexible layered structure 100 has a
plurality of LED receptacles 104 to which LEDs 125 are operatively
connected to other Surface Mount Technology (hereinafter "SMT")
electrical components 115 by electrical circuit 103 resulting from
circuitizing the flexible top conductive layer 101. In some
embodiments, the flexible bottom heat sink layer contains a
plurality of notches 116 to aid in bending the flexible layered
structure 100. A notch is intended to mean any indentation into
either the flexible top conductive layer or flexible bottom heat
sink layer, whether by cutting, pressing, abrading, etching or
otherwise. In some embodiments, the notch(es) are on the top or the
bottom of the flexible layered structure 100.
[0026] FIG. 1B illustrates a flexible layered structure 100 bent to
conform to at least a portion of a secondary heat sink 200. The
secondary heat sink may be solid, hollow, have radiating fins or
any construction suitable to desired use. The flexible layered
structure 100 has a plurality of defined positions 130 along the
longitudinal axis. The defined positions 130 may comprise a notch
to aid in bending the flexible layered structure 100. In an
alternative embodiment, a plurality of individual secondary heat
sinks can be bonded to defined positions of the flexible layered
structure bent or shaped in to a 3-D structure. In some
embodiments, the flexible layered structure also comprises a heat
sink adhesive layer. Referring now to FIG. 2, in addition to a
flexible top conductive layer 101, flexible dielectric middle layer
110 and a flexible bottom heat sink layer 112, the flexible layered
structure 100 comprises a heat sink adhesive layer 114 having a top
surface and a bottom surface. In such an embodiment, the top
surface of the heat sink adhesive layer 114 is bonded to the bottom
surface of the flexible bottom heat sink layer 112. In such an
embodiment, the bottom surface of the heat sink adhesive layer 114
is covered by a release liner 142. The release liner protects the
heat sink adhesive layer 114 until the release liner 142 can be
removed and a secondary heat sink 200 can be applied to the heat
sink adhesive layer 114 that is exposed.
[0027] FIG. 2 additionally illustrates another embodiment in which
the flexible layered structure 100 comprises an adhesive layer 12
which bonds the flexible top conductive layer 101 to the flexible
dielectric middle layer 110 and an adhesive layer 12' bonding the
flexible dielectric middle layer 110 to the flexible bottom heat
sink layer 112. In some embodiments, the adhesive layer 12 and the
adhesive layer 12' are the same material. In some embodiments, the
adhesive layer 12 and the adhesive layer 12' are different
materials.
[0028] In an alternative embodiment, the flexible layered structure
is conformed to at least a portion of a secondary heat sink and
bonded to the secondary heat sink by at least a portion of the heat
sink adhesive layer. In another embodiment, at least a portion of
the flexible layered structure is bent by at least 10 degrees. In
another embodiment, at least a portion of the flexible layered
structure is bent by at least 36 degrees. In another embodiment, at
least a portion of the flexible layered structure is bent by at
least 45 degrees. In another embodiment, at least a portion of the
flexible layered structure is bent by at least 60 degrees. In
another embodiment, at least a portion of the flexible layered
structure is bent by at least 72 degrees. In another embodiment, at
least a portion of the flexible layered structure is bent by at
least 90 degrees. In another embodiment, at least a portion of the
flexible layered structure is bent by at least 120 degrees. In yet
another alternative embodiment, at least one conductive layer
comprises an electrical circuit. In another embodiment, the defined
positions comprise a notch on the top or the bottom of the flexible
layered structure. In some embodiments, the defined positions
comprise a notch on the flexible bottom heat sink layer or the
flexible top conductive layer.
[0029] In another embodiment, at least 50 weight percent of the
flexible dielectric middle layer is a polyimide derived from at
least 30 mole percent aromatic dianhydride based upon total
dianhydride content of the polyimide and at least 30 mole percent
aromatic diamine based upon total diamine content of the polyimide.
In yet another alternative embodiment, the flexible dielectric
middle layer comprises 1 to 50 weight percent of a thermally
conductive filler, the thermally conductive filler comprises one or
more members of the group consisting of carbides, nitrides, borides
and oxides.
[0030] In some embodiments, the flexible layered structure further
comprises a heat sink adhesive layer having a top surface and a
bottom surface, the top surface of the heat sink adhesive layer
being bonded to the bottom surface of the flexible bottom heat sink
layer and the bottom surface of the heat sink adhesive layer being
covered by a release liner.
Flexible Dielectric Middle Layer
[0031] In some embodiments, the flexible dielectric middle layer is
a mechanically strong, heat resistant polymer, such as a polyester
(such as polyethylene terephthalate or polybutylene terephthalate),
fluoropolymer, acrylonitrile butadiene styrene ("ABS"),
polycarbonates ("PC"), polyamides ("PA"), polyphenylene oxide
("PPO"), polysulphone ("PSU"), polyetherketone ("PEK"),
polyetheretherketone ("PEEK"), polyphenylene sulfide ("PPS"),
polyoxymethylene plastic ("POM") , polyethylene naphthalate
("PEN"), or the like.
[0032] An adhesive layer can be provided on one or both sides (12
and/or 12') of the flexible dielectric middle layer. The flexible
dielectric middle layer is an electrically insulating thermally
conductive layer, wholly or partially providing an electrical
insulation barrier between the flexible top conductive layer and
the flexible bottom heat sink layer. In one embodiment, the
flexible dielectric middle layer is approximately 1 to 100 microns
thick, and can be of virtually any width or length. In some
embodiments, the flexible dielectric middle layer is from 4 to 100
microns thick. In some embodiments, the flexible dielectric middle
layer is a polyimide layer. In one embodiment, the polyimide layer
has a breakdown voltage of greater than 0.1, 0.5, 1, 5, 10 or 20
kilovolts (kV), and a (DMA) tensile strength at 480.degree. C. of
at least 100, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650,
700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400 or 1500
MPa. In one embodiment, the thermal conductivity of the polyimide
is at least 0.05, 0.1, 0.2, 0.3 0.4, 0.5, 1, 2 or 3 Watts per meter
per degree Kelvin (W/mK).
[0033] Examples of polyimide materials useful as the flexible
dielectric middle layer in accordance with the present disclosure
include polyimides derived from dianhydride type and diamine type
precursor materials. In some embodiments, at least 50 weight
percent of the flexible dielectric middle layer is a polyimide
derived from at least 30 mole percent aromatic dianhydride based
upon total dianhydride content of the polyimide and at least 30
mole percent aromatic diamine based upon total diamine content of
the polyimide. In some embodiments, the remaining diamine may be an
aliphatic diamine. As used herein, an "aliphatic diamine" is
intended to mean any organic diamine that does not meet the
definition of an aromatic diamine. In one embodiment, useful
aliphatic diamines have the following structural formula:
H.sub.2N--R--NH.sub.2, where R is an aliphatic moiety, such as a
substituted or unsubstituted hydrocarbon in a range from 4, 5, 6, 7
or 8 carbons to about 9, 10, 11, 12, 13, 14, 15, or 16 carbon
atoms, and in one embodiment the aliphatic moiety is a C.sub.6 to
C.sub.8 aliphatic.
[0034] In one embodiment, R is a C.sub.6 straight chain
hydrocarbon, known as hexamethylene diamine (HMD or
1,6-hexanediamine). In other embodiments, the aliphatic diamine is
an alpha, omega-diamine; such diamines can be more reactive than
alpha, beta-aliphatic diamines.
[0035] Useful aromatic diamines for example, are selected from the
group comprising:
[0036] 1. 2,2 bis-(4-aminophenyl) propane;
[0037] 2. 4,4'-diaminodiphenyl methane;
[0038] 3. 4,4'-diaminodiphenyl sulfide;
[0039] 4. 3,3'-diaminodiphenyl sulfone (3,3'-DDS);
[0040] 5. 4,4'-diaminodiphenyl sulfone (4,4'-DDS);
[0041] 6. 4,4'-diaminodiphenyl ether (4,4'-ODA);
[0042] 7. 3,4'-diaminodiphenyl ether (3,4'-ODA);
[0043] 8. 1,3-bis-(4-aminophenoxy) benzene (APB-134 or RODA);
[0044] 9. 1,3-bis-(3-aminophenoxy) benzene (APB-133);
[0045] 10. 1,2-bis-(4-aminophenoxy) benzene;
[0046] 11. 1,2-bis-(3-aminophenoxy) benzene;
[0047] 12. 1,4-bis-(4-aminophenoxy) benzene;
[0048] 13. 1,4-bis-(3-aminophenoxy) benzene;
[0049] 14. 1,5-diaminonaphthalene;
[0050] 15. 1,8-diaminonaphthalene;
[0051] 16. 2,2'-bis(trifluoromethyl)benzidine;
[0052] 17. 4,4'-diaminodiphenyldiethylsilane;
[0053] 18. 4,4'-diaminodiphenylsilane;
[0054] 19. 4,4'-diaminodiphenylethylphosphine oxide;
[0055] 20. 4,4'-diaminodiphenyl-N-methyl amine;
[0056] 21. 4,4'-diaminodiphenyl-N-phenyl amine;
[0057] 22. 1,2-diaminobenzene (OPD);
[0058] 23. 1,3-diaminobenzene (MPD);
[0059] 24. 1,4-diaminobenzene (PPD);
[0060] 25. 2,5-dimethyl-1,4-diaminobenzene;
[0061] 26. 2-(trifluoromethyl)-1,4-phenylenediamine;
[0062] 27. 5-(trifluoromethyl)-1,3-phenylenediamine;
[0063] 28. 2,2-Bis[4-(4-aminophenoxy)phenyl]-hexafluoropropane
(BDAF);
[0064] 29. 2,2-bis(3-aminophenyl)
1,1,1,3,3,3-hexafluoropropane;
[0065] 30. benzidine;
[0066] 31. 4,4'-diaminobenzophenone;
[0067] 32. 3,4'-diaminobenzophenone;
[0068] 33. 3,3'-diaminobenzophenone;
[0069] 34. m-xylylene diamine;
[0070] 35. bisaminophenoxyphenylsulfone;
[0071] 36. 4,4'-isopropylidenedianiline;
[0072] 37. N,N-bis-(4-aminophenyl) methylamine;
[0073] 38. N,N-bis-(4-aminophenyl) aniline
[0074] 39. 3,3'-dimethyl-4,4'-diaminobiphenyl;
[0075] 40. 4-aminophenyl-3-aminobenzoate;
[0076] 41. 2,4-diaminotoluene;
[0077] 42. 2,5-diaminotoluene;
[0078] 43. 2,6-diaminotoluene;
[0079] 44. 2,4-diamine-5-chlorotoluene;
[0080] 45. 2,4-diamine-6-chlorotoluene;
[0081] 46. 4-chloro-1,2-phenylenediamine;
[0082] 47. 4-chloro-1,3-phenylenediamine;
[0083] 48. 2,4-bis- (beta-amino-t-butyl) toluene;
[0084] 49. bis-(p-beta-amino-t-butyl phenyl) ether;
[0085] 50. p-bis-2-(2-methyl-4-aminopentyl) benzene;
[0086] 51. 1-(4-aminophenoxy)-3-(3-aminophenoxy) benzene;
[0087] 52. 1-(4-aminophenoxy)-4-(3-aminophenoxy) benzene;
[0088] 53. 2,2-bis-[4-(4-aminophenoxy)phenyl] propane (BAPP);
[0089] 54. bis-[4-(4-aminophenoxy)phenyl] sulfone (BAPS);
[0090] 55. 2,2-bis[4-(3-aminophenoxy)phenyl] sulfone (m-BAPS);
[0091] 56. 4,4'-bis-(aminophenoxy)biphenyl (BAPB);
[0092] 57. bis-(4-[4-aminophenoxy]phenyl) ether (BAPE);
[0093] 58. 2,2'-bis-(4-aminophenyl)-hexafluoropropane (6F
diamine);
[0094] 59.
bis(3-aminophenyl)-3,5-di(trifluoromethyl)phenylphosphine oxide
[0095] 60. 2,2'-bis-(4-phenoxy aniline) isopropylidene;
[0096] 61. 2,4,6-trimethyl-1,3-diaminobenzene;
[0097] 62. 4,4'-diamino-2,2'-trifluoromethyl diphenyloxide;
[0098] 63. 3,3'-diamino-5,5'-trifluoromethyl diphenyloxide;
[0099] 64. 4,4'-trifluoromethyl-2,2'-diaminobiphenyl;
[0100] 65. 4,4'-oxy-bis-[(2-trifluoromethyl) benzene amine];
[0101] 66. 4,4'-oxy-bis-[(3-trifluoromethyl) benzene amine];
[0102] 67. 4,4'-thio-bis-[(2-trifluoromethyl) benzene-amine];
[0103] 68. 4,4'-thiobis-[(3-trifluoromethyl) benzene amine];
[0104] 69. 4,4'-sulfoxyl-bis-[(2-trifluoromethyl) benzene
amine;
[0105] 70. 4,4'-sulfoxyl-bis-[(3-trifluoromethyl) benzene
amine];
[0106] 71. 4,4'-keto-bis-[(2-trifluoromethyl) benzene amine];
[0107] 72. 9,9-bis(4-aminophenyl)fluorene;
[0108] 73. 1,3-diamino-2,4,5,6-tetrafluorobenzene;
[0109] 74. 3,3'-bis(trifluoromethyl)benzidine;
[0110] 75. 3,3'-diaminodiphenylether;
[0111] 76. and the like.
[0112] Useful aliphatic diamines used in conjunction with the
aromatic diamine include (but are not limited to) 1,6-hexamethylene
diamine, 1,7-heptamethylene diamine, 1,8-octamethylenediamine,
1,9-nonamethylenediamine, 1,10-decamethylenediamine (DMD),
1,11-undecamethylenediamine, 1,12-dodecamethylenediamine (DDD),
1,16-hexadecamethylenediamine,
1,3-bis(3-aminopropyl)-tetramethyldisiloxane,
.alpha.,.omega.-bis(3-aminopropyl) polydimethylsiloxane,
isophoronediamine, and combinations thereof. Any cycloaliphatic
diamine can also be used, an example of which is 1, 4 diamino
cyclohexane.
[0113] In one embodiment of the present invention (in order to
achieve a low temperature bonding) diamines comprising ether
linkages and or diamines comprising aliphatic functional groups are
used. The term low temperature bonding is intended to mean bonding
two materials in a temperature range of from about 180, 185, or
190.degree. C. to about 195, 200, 205, 210, 215, 220, 225, 230,
235, 240, 245 or 250.degree. C.
[0114] Similarly, the term dianhydride as used herein is intended
to mean a component that reacts with (or is complimentary to) a
diamine, and in combination is capable of reacting to form an
intermediate polyamic acid (which can then be cured into a
polyimide). Depending upon the context, "anhydride" as used herein
can mean not only an anhydride moiety per se, but also a precursor
to an anhydride moiety, such as: (i) a pair of carboxylic acid
groups (which can be converted to anhydride by a de-watering or
similar-type reaction); or (ii) an acid halide (e.g., chloride)
ester functionality (or any other functionality presently known or
developed in the future which is) capable of conversion to
anhydride functionality.
[0115] Depending upon context, "dianhydride" can mean: (i) the
unreacted form (i.e., a dianhydride monomer, whether the anhydride
functionality is in a true anhydride form or a precursor anhydride
form, as discussed in the prior above paragraph); (ii) a partially
reacted form (i.e., the portion or portions of an oligomer or other
partially reacted or precursor polyimide composition reacted from
or otherwise attributable to dianhydride monomer) or (iii) a fully
reacted form (the portion or portions of the polyimide derived from
or otherwise attributable to dianhydride monomer).
[0116] The dianhydride can be functionalized with one or more
moieties, depending upon the particular embodiment selected in the
practice of the present invention. Indeed, the term "dianhydride"
is not intended to be limiting (or interpreted literally) as to the
number of anhydride moieties in the dianhydride component. For
example, (i), (ii) and (iii) (in the paragraph above) include
organic substances that may have two, one, or zero anhydride
moieties, depending upon whether the anhydride is in a precursor
state or a reacted state. Alternatively, the dianhydride component
may be functionalized with additional anhydride type moieties (in
addition to the anhydride moieties that react with diamine to
provide a polyimide). Such additional anhydride moieties could be
used to crosslink the polymer or to provide other functionality to
the polymer.
[0117] Useful dianhydrides of the present invention include
aromatic dianhydrides. These aromatic dianhydrides include, (but
are not limited to):
[0118] 1. pyromellitic dianhydride (PMDA);
[0119] 2. 3,3',4,4'-biphenyl tetracarboxylic dianhydride
(BPDA);
[0120] 3. 3,3',4,4'-benzophenone tetracarboxylic dianhydride
(BTDA);
[0121] 4. 4,4'-oxydiphthalic anhydride (ODPA);
[0122] 5. 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride
(DSDA);
[0123] 6. 2,2-bis(3,4-dicarboxyphenyl)
1,1,1,3,3,3-hexafluoropropane dianhydride (6FDA);
[0124] 7. 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic
anhydride) (BPADA);
[0125] 8. 2,3,6,7-naphthalene tetracarboxylic dianhydride;
[0126] 9. 1,2,5,6-naphthalene tetracarboxylic dianhydride;
[0127] 10. 1,4,5,8-naphthalene tetracarboxylic dianhydride;
[0128] 11. 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic
dianhydride;
[0129] 12. 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic
dianhydride;
[0130] 13. 2,3,3',4'-biphenyl tetracarboxylic dianhydride;
[0131] 14. 2,2',3,3'-biphenyl tetracarboxylic dianhydride;
[0132] 15. 2,3,3',4'-benzophenone tetracarboxylic dianhydride;
[0133] 16. 2,2',3,3'-benzophenone tetracarboxylic dianhydride;
[0134] 17. 2,2-bis(3,4-dicarboxyphenyl) propane dianhydride;
[0135] 18. 1,1-bis(2,3-dicarboxyphenyl) ethane dianhydride;
[0136] 19. 1,1-bis(3,4-dicarboxyphenyl) ethane dianhydride;
[0137] 20. bis-(2,3-dicarboxyphenyl) methane dianhydride;
[0138] 21. bis-(3,4-dicarboxyphenyl) methane dianhydride;
[0139] 22. 4,4'-(hexafluoroisopropylidene) diphthalic
anhydride;
[0140] 23. bis-(3,4-dicarboxyphenyl) sulfoxide dianhydride;
[0141] 24. tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride;
[0142] 25. pyrazine-2,3,5,6-tetracarboxylic dianhydride;
[0143] 26. thiophene-2,3,4,5-tetracarboxylic dianhydride;
[0144] 27. phenanthrene-1,8,9,10-tetracarboxylic dianhydride;
[0145] 28. perylene-3,4,9,10-tetracarboxylic dianhydride;
[0146] 29. bis-1,3-isobenzofurandione;
[0147] 30. bis-(3,4-dicarboxyphenyl) thioether dianhydride;
[0148] 31.
bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylicdianhydride;
[0149] 32. 2-(3',4'-dicarboxyphenyl) 5,6-dicarboxybenzimidazole
dianhydride;
[0150] 33. 2-(3',4'-dicarboxyphenyl) 5,6-dicarboxybenzoxazole
dianhydride;
[0151] 34. 2-(3',4'-dicarboxyphenyl) 5,6-dicarboxybenzothiazole
dianhydride;
[0152] 35. bis-(3,4-dicarboxyphenyl) 2,5-oxadiazole
1,3,4-dianhydride;
[0153] 36. bis-2,5-(3',4'-dicarboxydiphenylether) 1,3,4-oxadiazole
dianhydride;
[0154] 37. bis-2,5-(3',4'-dicarboxydiphenylether) 1,3,4-oxadiazole
dianhydride;
[0155] 38.
5-(2,5-dioxotetrahydro)-3-methyl-3-cyclohexene-1,2-dicarboxylic
anhydride;
[0156] 39. trimellitic anhydride
2,2-bis(3',4'-dicarboxyphenyl)propane dianhydride;
[0157] 40. 1,2,3,4-cyclobutane dianhydride;
[0158] 41. 2,3,5-tricarboxycyclopentylacetic acid dianhydride;
[0159] 42. their acid ester and acid halide ester derivatives;
[0160] 43. and the like.
[0161] The dianhydride and diamine components of the present
invention are particularly selected to provide the polyimide binder
with specifically desired properties. One such useful property is
for the polyimide binder to have a certain glass transition
temperature (Tg). A useful Tg can be between (and optionally
including) any two of the following numbers: 350, 325, 300, 275,
250, 240, 230, 220, 210, 200, 190, 180, 170, 160, 150, 140, 130,
120, 110 and 100.degree. C. Another useful range, if adherability
is less important than other properties, is between (and optionally
including) any of the following: 550, 530, 510, 490, 470, 450, 430,
410, 390, 370, 350, 330, 310, 290, 270, and 250.degree. C. In some
cases, a polysiloxane diamine can be used in a mole ratio (compared
to the second diamine) so that the polyimide binder has lower Tg.
In another case, where low Tg is required, less polysiloxane
diamine can be used so long as certain flexible diamines are
chosen. Useful flexible diamines here can include APB-134, APB-133,
3,4'-ODA, BAPP, BAPE, BAPS and many aliphatic diamines. As such,
the selection of dianhydride and diamine component is important to
customize what final properties of the polymer binder are
specifically desired.
[0162] In one embodiment of the present invention useful
dianhydrides include BPADA, DSDA, ODPA, BPDA, BTDA, 6FDA, and PMDA
or mixtures thereof. These dianhydrides are readily commercially
available and generally provide acceptable performance.
[0163] In some embodiments, the flexible dielectric middle layer is
a polyimide derived from pyromellitic dianhydride,
3,3',4,4'-biphenyl tetracarboxylic dianhydride,
4,4'-diaminodiphenyl ether and paraphenylene diamine. In some
embodiments, the flexible dielectric middle layer is a polyimide
derived from 3,3',4,4'-benzophenone tetracarboxylic dianhydride,
3,3',4,4'-biphenyl tetracarboxylic dianhydride,
4,4'-diaminodiphenyl ether and paraphenylene diamine.
[0164] Ultimately, the precursor (polyamic acid) is converted into
a high-temperature polyimide material having a solids content
greater than about 99.5 weight percent. At some point in the
process, the viscosity of the mixture is increased beyond the point
where the thermally conductive filler material can be blended with
the polyimide precursor. Depending upon the particular embodiment
herein, the viscosity of the mixture can possibly be lowered again
by diluting the material, perhaps sufficiently enough to allow
dispersion of the thermally conductive filler material into the
polyimide precursor.
[0165] Polyamic acid solutions can be converted to polyimides using
processes and techniques commonly known in the art, such as, heat
or conventional polyimide conversion chemistry. Such polyimide
manufacturing processes are well known. Any conventional or
non-conventional polyimide manufacturing process can be appropriate
for use in accordance with the present invention provided that a
precursor material is available having a sufficiently low viscosity
to allow thermally conductive filler material to be mixed.
Likewise, if the polyimide is soluble in its fully imidized state,
thermally conductive filler can be dispersed at this stage prior to
forming into the final composite.
Flexible Dielectric Middle Layer Filler
[0166] In some embodiments, the flexible dielectric middle layer
comprises from 1 to 50 weight percent of a thermally conductive
filler. The thermally conductive filler comprises one or more
members of the group consisting of carbides, nitrides, borides and
oxides which can be added to the polyamic acid prior to imidization
to thereby create a filled polyimide. The filled polyimide will
tend to have lower thermal resistance, thereby generally allowing
more unwanted heat to flow away from the LEDs. In one embodiment,
the polyimide film of the present disclosure comprises a thermally
conductive filler:
[0167] 1. being less than 5 microns (and in some embodiments, less
than 2000, 1000, 800, or 500 nanometers in at least one dimension
(since thermally conductive fillers can have a variety of shapes in
any dimension and since thermally conductive filler shape can vary
along any dimension, the "at least one dimension" is intended to be
a numerical average along that dimension);
[0168] 2. having an average aspect ratio equal to or greater than
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 to 1;
[0169] 3. being less than 100, 95, 90, 85, 80, 75, 70, 65, 60, 55,
50, 45, 40, 35, 30, 25, 20, 15 or 10 percent of the film thickness
in all dimensions; and
[0170] 4. being present in an amount between and optionally
including any two of the following percentages: 5, 10, 15, 20, 25,
30, 35, 40, 45, 50, 55 and 60 volume percent of the polyimide
film.
[0171] Suitable thermally conductive fillers are generally stable
at temperatures above 300, 350, 400, 425 or 450.degree. C., and in
some embodiments do not significantly decrease the electrical
insulation properties of the film. In some embodiments, the
thermally conductive filler is selected from a group consisting of
needle-like thermally conductive fillers (acicular), fibrous
thermally conductive fillers, platelet thermally conductive fillers
and mixtures thereof. In one embodiment, the thermally conductive
filler is substantially non-aggregated. The thermally conductive
filler can be hollow, porous, or solid.
[0172] In some embodiments, the thermally conductive filler is
selected from the group consisting of oxides (e.g., oxides
comprising silicon, magnesium and/or aluminum), nitrides (e.g.,
nitrides comprising boron and/or silicon), carbides (e.g., carbides
comprising tungsten and/or silicon), borides (e.g., titanium
diboride) and combinations thereof. In some embodiments, the
thermally conductive filler comprises titanium dioxide, talc, SiC,
Al.sub.2O.sub.3 or mixtures thereof. In some embodiments, the
thermally conductive filler is less than (as a numerical average)
50, 25, 20, 15, 12, 10, 8, 6, 5, 4, or 2 microns in all dimensions.
In some embodiments, the thermally conductive filler is a
sub-micron thermally conductive filler.
[0173] In yet another embodiment, carbon fiber and graphite can be
used in combination with thermally conductive fillers to increase
mechanical properties. However in one embodiment, the loading of
graphite, carbon fiber and/or electrically conductive fillers may
need to be below the percolation threshold (perhaps less than 10
volume percent), since graphite and carbon fiber can diminish
electrical insulation properties and in some embodiments,
diminished electrical insulation properties are not desirable. In
yet another embodiment, low amounts of carbon fiber and graphite
may be used in combination with other fillers.
[0174] In some embodiments, the thermally conductive filler is
coated with a coupling agent. In some embodiments, the thermally
conductive filler is coated with an aminosilane coupling agent. In
some embodiments, the thermally conductive filler is coated with a
dispersant. In some embodiments, the thermally conductive filler is
coated with a combination of a coupling agent and a dispersant. In
some embodiments, the thermally conductive filler is coated with a
coupling agent, a dispersant or a combination thereof.
Alternatively, the coupling agent and/or dispersant can be
incorporated directly into the film and not necessarily coated onto
the thermally conductive filler. In some embodiments, the thermally
conductive filler comprises acicular titanium dioxide, at least a
portion of which is coated with an aluminum oxide.
[0175] In some embodiments, the thermally conductive filler is
chosen so that it does not itself degrade or produce off-gasses at
the desired processing temperatures. Likewise in some embodiments,
the thermally conductive filler is chosen so that it does not
contribute to degradation of the polymer.
[0176] In one embodiment, thermally conductive filler composites
(e.g. single or multiple core/shell structures) can be used, in
which one oxide encapsulates another oxide in one particle. In some
embodiments, the thermally conductive filler is selected from the
group consisting of spherical or near spherical shaped fillers,
platelet-shaped fillers, needle-like fillers, fibrous fillers and
mixtures thereof. In some embodiments, the platelet-shaped fillers
and needle-like fillers and fibrous fillers will maintain or lower
the CTE of the polyimide layer while still increasing the storage
modulus. Useful fillers should be stable at temperatures of at
least 105.degree. C.) and not substantially decrease the electrical
insulation of the polyimide film. In some embodiments, the
thermally conductive filler is selected from the group consisting
of mica, talc, boron nitride, wollastonite, clays, calcinated
clays, silica, alumina, platelet alumina, glass flake, glass fiber
and mixtures thereof. The thermally conductive filler may be
treated or untreated.
[0177] In some embodiments, the thermally conductive filler is
selected from a group consisting of oxides (e.g., oxides comprising
silicon, titanium, magnesium and/or aluminum), nitrides (e.g.,
nitrides comprising boron and/or silicon) or carbides (e.g.,
carbides comprising tungsten and/or silicon). In some embodiments,
the thermally conductive filler comprises oxygen and at least one
member of the group consisting of aluminum, silicon, titanium,
magnesium and combinations thereof. In some embodiments, the
thermally conductive filler comprises platelet talc, acicular
titanium dioxide, and/or acicular titanium dioxide, at least a
portion of which is coated with an aluminum oxide. In some
embodiments the thermally conductive filler is less than 50, 25,
20, 15, 12, 10, 8, 6, 5, 4, 2, 1, 0.8, 0.75, 0.65, 0.5, 0.4, 0.3,
or 0.25 microns in all dimensions.
[0178] Depending on the particular filler used, too low a filler
loading may have minimal impact on the film properties, while too
high a filler loading may cause the polyimide to become brittle.
Ordinary skill and experimentation may be necessary in selecting
any particular filler in accordance with the present disclosure,
depending upon the particular application selected. In some
embodiments, the filler is present in an amount between (and
optionally including) any two of the following weight percentages:
5, 10, 15, 10, 25, 30, 35, 40, 45, 50, 55, 60, 65 and 70 weight
percent of the total weight of the polyimide flexible dielectric
middle layer.
[0179] In some embodiments, the crystallinity, and amount of
crosslinking of a polyimide can aid in storage modulus retention.
In another embodiment, when the flexible dielectric middle layer is
a polyimide, the flexible dielectric middle layer comprises a
thermally stable reinforcing fabric, paper, sheet, scrim and
combinations thereof in order to increase the storage modulus of
the polyimide. In one embodiment, when the flexible dielectric
middle layer is a polyimide, the storage modulus (DMA) at
480.degree. C. is greater than (and optionally equal to) any of the
following numbers: 190, 200, 250, 300, 350, 400, 450, 500, 550,
600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300,
1400 or 1500 MPa.
[0180] The polyimides of the present disclosure should have high
thermal stability so that they do not substantially degrade, lose
weight and exhibit diminished mechanical properties, as well as, do
not give off significant volatiles during the deposition process.
In some embodiments, the polyimide has an isothermal weight loss of
less than 1% measured by thermogravimetric analysis at 500.degree.
C. over 30 minutes under inert conditions, such as in a substantial
vacuum, in a nitrogen or any inert gas environment.
[0181] Polyimides of the present disclosure have high dielectric
strength. In some embodiments, the dielectric strength of
polyimides is much higher compared to common inorganic insulators.
In some embodiments, flexible dielectric middle layer of the
present disclosure is a polyimide having a dielectric strength
greater than 39.4 KV/mm. In some embodiments, flexible dielectric
middle layer of the present disclosure is a polyimide having a
dielectric strength greater than 213 KV/mm.
[0182] It is important that the flexible dielectric middle layer be
as free as possible of pinhole or other defects (foreign particles,
conductive particles, gels, filler agglomerates and other
contaminates) that could adversely impact the electrical integrity
and dielectric strength of the flexible dielectric middle layer.
The term "pinhole" as used herein includes any small holes that
result from non-uniformities in a layer or otherwise arising from
the manufacturing process.
[0183] The flexible dielectric middle layer of the present
disclosure should be thin so as to not add excessive weight or cost
but thick enough to provide high electrical insulation at operating
voltages. In some embodiments, the flexible dielectric middle layer
has a thickness between (and optionally including) any two of the
following thicknesses 8, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100
microns.
[0184] The flexible dielectric middle layer can be made thicker in
an attempt to decrease defects or their impact on the layer's
integrity or alternatively, multiple flexible dielectric middle
layers may be used. Thin multiple layers can be advantageous over a
single layer of the same thickness. Such multilayers can greatly
eliminate the occurrence of through-film pinholes or defects,
because the likelihood of defects that overlap in each of the
individual layers is extremely small and therefore a defect in any
one of the layers is much less likely to cause an electrical
failure through the entire thickness of the flexible dielectric
middle layer. In some embodiments, the flexible dielectric middle
layer comprises two or more layers of polyimide. In some
embodiments, the polyimide layers are the same or different. In
some embodiments, the polyimide layers independently may comprise a
thermally stable filler, reinforcing fabric, inorganic (e.g., mica)
paper, sheet, scrim and/or combinations thereof.
Adhesive Layer(s)
[0185] In addition to the flexible dielectric middle layer, the
flexible dielectric middle layer optionally also comprises an
optional adhesive layer 12 and/or an optional adhesive layer 12'.
Such adhesive layer (or layers) can be any adhesive now known or
developed in the future for bonding polyimide to metal. In one
embodiment, the adhesive layer comprises a thermoplastic polyimide
polymer comprising at least 20 mole percent aliphatic moieties and
having a glass transition temperature below 350, 300, 250, 225,
200, 190, 180, 170, 160 or 150.degree. C.
[0186] In some embodiments, the adhesive layer 12 is polyimide
derived from 4,4'-oxydiphthalic anhydride, pyromellitic dianhydride
and 1,3-bis-(4-aminophenoxy) benzene. In some embodiments, the
adhesive layer 12' is polyimide derived from 4,4'-oxydiphthalic
anhydride, pyromellitic dianhydride and 1,3-bis-(4-aminophenoxy)
benzene.
[0187] The polyimide provides structure integrity and mechanical
strength to the flexible dielectric middle layer, while the
adhesive layer(s) 12 and/or 12' provide fracturability to allow
improved bending capability with diminished necking, bulging or
other unwanted incongruity otherwise induced by the bending of the
flexible layered structure.
[0188] In one embodiment, the flexible layered structure comprises
a top adhesive layer bonding the flexible top conductive layer to
the flexible dielectric middle layer. In another embodiment, the
flexible layered structure comprises a bottom adhesive layer
bonding the flexible dielectric middle layer to the flexible bottom
heat sink layer. In yet another embodiment, the flexible layered
structure comprises a top adhesive layer bonding the flexible top
conductive layer to the flexible dielectric middle layer and a
bottom adhesive layer bonding the flexible dielectric middle layer
to the flexible bottom heat sink layer.
[0189] Flexible TOP Conductive Layer and Flexible Bottom Heat Sink
Layer
[0190] Prior to circuitizeation, in one embodiment the flexible top
conductive layer is a metal, such as copper approximately 4 to 200
microns in thickness. Although copper is a preferred conductive
material, it is recognized that other suitable electrically
conductive materials such as, but not limited to, aluminum could be
used. The top conductive copper layer can be circuitized to include
a thermally conductive printed or etched electrical circuit using
standard electrical circuit design tools and techniques well known
in the art and is then optionally coated with a protective coating
using standard solder masking and labeling techniques well known in
the art. An example of a suitable protective coating that could be
used is PYRALUX.RTM. PC1000 Flexible Photoimageable Coverlay by
DuPont of Wilmington Del.
[0191] The flexible top conductive layer is designed in such a way
as to provide receptacles and mounting surfaces for LEDs and other
SMT electrical components proximate the top surface. The flexible
top conductive layer includes a plurality of LED receptacles to
which LEDs are operatively connected. The electrical circuit and
the LED receptacles can be made of copper and receive a lead free
hot air solder level (HASL) or organic solder protection (OSP)
coating. These coatings protect the flexible top conductive layer
surface from oxidization during storage, prior to assembly,
enhancing solderability of SMT components.
[0192] In one embodiment, prior to circuitization, the bottom
flexible bottom heat sink layer is copper with a thickness greater
than 20 microns. Although copper is a preferred material, it is
recognized that other suitable electrically conductive materials
such as, but not limited to, aluminum could be used. In one
embodiment, the flexible bottom heat sink layer is modified into a
heat spreading copper circuit laterally and along its longitudinal
axis proximate the bottom surface using standard electrical circuit
design tools and techniques well known in the art to rapidly spread
the heat through the flexible bottom heat sink layer. In one
embodiment, the flexible bottom heat sink layer includes a
thermally conductive electrical circuit printed or etched using
solder mask printing, photo etching, and/or solder masking
techniques well known in the art for producing electrical circuits.
Such electrical circuit can be used to conduct heat away from the
top conductive surface and can also be used as an electrical
circuit. In alternative embodiments, the flexible bottom heat sink
layer is a solid layer with no electrical circuit.
[0193] In one embodiment, the flexible top heat sink layer is
electrically connected to the bottom heat sink layer by means of
plated through holes. In one embodiment, the plated through holes
are filled with thermally conductive filler to enhance thermal path
from the flexible top to flexible bottom heat sink layer.
[0194] Optionally, the flexible layered structure may also include
a heat sink adhesive layer. The heat sink adhesive layer can be a
two-sided thermally conductive tape with two removable layers of
protective backing. One of the removable layers of protective
backing is removed to expose one side of the heat sink adhesive
layer, which is then operatively connected to the bottom surface of
the flexible bottom heat sink layer. When it is later desired to
operatively connect the flexible layered structure to a secondary
heat sink, the second removable layer of release liner is removed
to expose the other side of the heat sink adhesive layer. The heat
sink adhesive layer can thereby provide thermal contact between the
flexible layered structure and the secondary heat sink and the heat
sink adhesive layer is optionally capable of filling large voids
and air gaps to improve thermal conductivity.
[0195] An example of a suitable heat sink adhesive layer is 3M.RTM.
Thermally Conductive Adhesive Transfer Tape 8810. Although a
two-sided thermally conductive tape is used in this particular
embodiment, it is recognized that other suitable thermally
conductive connecting materials could be used.
[0196] In one embodiment, the flexible layered structure is an
integral, flexible layered structure that is sufficiently flexible
to be easily bent in angles of 1 to 180 degrees and/or is
sufficiently flexible to substantially or fully follow the contour
of complex, three dimensional shapes. In one embodiment, the
flexible layered structure 100 can bend laterally along a plurality
of defined positions spaced along the length of the longitudinal
axis to an outside bend radius of less than 2.0 mm (0.078 inch) and
can be wrapped about a longitudinal axis of a hub 119 of a reel
118, as shown in FIG. 3. Although only one position is shown, it is
recognized that there are a plurality of positions spaced along the
length of the longitudinal axis. In one embodiment, the flexible
layered structure can also bend to conform to localized secondary
heat sink surface flatness variations having an outside bend radius
of less than at least 2.0 mm (0.078 inch). By conforming to
variations in heat sink base material shapes, heat transfer from
the LEDs generally is greatly improved.
[0197] In some embodiments, the flexible layered structure is
conformed to at least a portion of a secondary heat sink and bonded
to the secondary heat sink by at least a portion of the heat sink
adhesive layer. In some embodiments, the flexible layered structure
being at least partially bent around a longitudinal axis.
[0198] The flexible layered structure can be pre-populated with a
plurality of LEDs and other Surface Mount Technology (hereinafter
"SMT") electrical components well known in the art for completion
of a solid state lighting electrical circuit cable of producing
light. An example of a pre-populated flexible layered structure
could include the flexible layered structure, a plurality of LEDs
positioned longitudinally along the circuit approximately every few
centimeters, linear drivers positioned longitudinally between every
sixth LED and seventh LED, and connectors for power placed
longitudinally approximately every meter. An example of a suitable
LED is XPE manufactured by CREE Incorporated of Raleigh, N.C. An
example of a suitable liner driver is NUD4001 manufactured by ON
Semiconductor of Phoenix, Ariz.
[0199] In one embodiment, the flexible layered structure may be cut
to any desired length, cutting at pre-defined electrical circuit
locations according to the electrical circuit's design. In one
embodiment, a connector is operatively connected to the flexible
layered structure to provide power to the LED system, and if it is
desired to connect two flexible layered structures together, a
board to board connector could be used. Such connectors are well
known in the art.
[0200] Heat generated proximate the LED p-n junction is conducted
from the LED chip to the LED heat sink slug as designed by the LED
manufacturer. The LED heat sink slug typically is less than 0.25
inch (0.635 centimeter) in diameter or 0.050 inch (0.127
centimeter) squared proximate the LED's base. When electrically
driven, the heat generated by the LED and transferred to the LED
heat sink slug can range from 1 to 5 Watts or more per 0.8 inch
(2.032 centimeters) squared when applied to an adequate assembly
heat sink. It is important to remove the heat away from the LED p-n
junction to maintain the manufactures' specifications for normal
operation proximate the p-n junction.
[0201] The flexible layered structure provides a path for heat to
be spread through the flexible top conductive layer, through the
flexible dielectric middle layer, and into the flexible bottom heat
sink layer. The flexible bottom heat sink layer can provide a path
for the heat to spread laterally and longitudinally proximate over
the top surface of a secondary heat sink to which the flexible
layered structure can be operatively connected. In some
embodiments, the heat sink adhesive layer is thermally conductive.
The heat sink adhesive layer provides an interface layer which
fills the voids between the flexible bottom heat sink layer and the
mounting surface of the secondary heat sink. Should there be any
voids or air gaps in the mounting surface of the heat sink, the
heat sink adhesive layer can be used to fill in the voids and air
gaps, even if less than 50 microns (in at least one dimension),
thus reducing the amount of voids and air gaps and increasing the
amount of thermal transfer to the heat sink. The flexible layered
structure can therefore substantially conform to the heat sink and
thereby provide the necessary thermal transfer capabilities
necessary for high wattage LED lighting systems. Should it be
desired to connect a flexible layered structure to another flexible
layered structure, a board to board connector could be used.
[0202] The flexible layered structure can be advantageous for any
one of a number of reasons. For example, the circuit design
proximate the top surface of the flexible top conductive layer can
be made relatively thin and therefore less expensively, since heat
can be dissipated without a large amount of heat absorbing metal in
the electrical circuit or the flexible top conductive layer. The
flexible top conductive layer and the flexible dielectric middle
layer can be made sufficiently thin to allow easy flexibility and
bending or twisting while maintaining electrical integrity. The
flexible bottom heat sink layer can also be made relatively thin to
allow flexibility and bending, since additional heat dissipation is
possible by adhering the flexible bottom heat sink layer to a
secondary heat sink separate and apart from the flexible layered
structure.
[0203] In this way, the flexible layered structure can be
configured into a three dimensional lighting configuration and then
incorporated into a lighting structure comprising a secondary heat
sink. With an appropriate secondary heat sink, it is possible to
obtain a thermal conductivity of greater than 300, 400, 500, 600,
700 or 750 Watts per meter per degree Kelvin (W/m.degree.K).
[0204] The flexible dielectric middle layer provides electrical
isolation of the LED for proper electrical functionality with
breakdown voltage greater than 2, 3, 4, 5, 6, 7.5 kV or greater.
Also, the adhesive layers can be thermally conductive adhesive,
such as by loading with thermally conductive filler, thereby
improving the heat transfer path to the flexible bottom heat sink
layer and also the optional secondary heat sink.
Secondary Heat Sink
[0205] In one embodiment, the secondary heat sink is a plurality of
separate secondary heat sinks that are bonded to the flexible
layered structure. The flexible layered structure can be wrapped
around, thereby forming a cylinder type configuration
interconnecting the secondary heat sink. In some embodiments, the
electrical circuit on the flexible top conductive layer of the
flexible layered structure is sufficiently robust to allow such
bending and twisting without detriment to the electrical
connections between the LED lights.
[0206] Hence, a series of secondary heat sink can be placed in a
plane and the flexible layered structure of the present disclosure
can be pulled over the assembly components, a release liner can be
removed and the exposed heat sink adhesive layer can then be
pressed onto the secondary heat sink, thereby adhering the
secondary heat sink to the flexible layered structure. The
combination can then be bent or otherwise manipulated into a final
configuration to provide a lighting assembly where at least two of
the LED lights shine in different directions.
[0207] Due to the flexibility of the flexible layered structure,
virtually any configuration of a secondary heat sink can be used
over which or around which the flexible layered structure of the
present disclosure can be bonded. The flexible layered structure is
sufficiently pliable to accommodate virtually any three dimensional
configuration of a secondary heat sink. In one embodiment, the
secondary heat sink can be part of a "screw in," "plug in" or
similar-type housing, so the final assembly can be configured as a
replacement for a conventional light bulb.
[0208] Operatively connecting the pre-populated, flexible layered
structure to the secondary heat sink includes removing the flexible
layered structure from its storage container, laying out a desired
length of the flexible layered structure from a reel and cutting
the desired length (if applicable), removing the release liner (if
applicable), placing the flexible layered structure onto a desired
location on the secondary heat sink, and applying pressure onto the
flexible layered structure proximate the flexible top conductive
layer avoiding any sensitive electrical components (if applicable).
In one embodiment, standard electro static discharge ("ESD")
precautions should be followed. In some embodiments, direct
pressure should not be applied to pressure sensitive devices, such
as LEDs with optical components. In one embodiment, manual pressure
with one's finger(s) of approximately 13.8 kilo-Newtons/square
meter) along 90% or more of the flexible layered structure should
be sufficient for connection to the heat sink. In some embodiments,
a roller or other applicator device could also be used. In one
embodiment, once the flexible layered structure 100 is connected to
a heat sink, the circuits can be connected to a termination board,
which supplies power to the system as is well known in the art. If
an adhesive layer is not used, the flexible layered structure could
be connected with thermal paste adhesive, thermal grease with
mechanical fastening, or other suitable securing means.
[0209] The flexible layered structure can be a low cost, flexible
structure consisting in part of a very thin and flexible printed
circuit substrate and a thermally conductive adhesive layer, which
when operatively connected to a secondary heat sink produces a
highly useful thermal interface with the secondary heat sink, thus
achieving overall advantageous system thermal performance. The
circuit structure is designed in such a way as to allow the copper
pads on the flexible top conductive layer to spread heat across the
top surface. In one embodiment, the thin, flexible dielectric
middle layer allows conduction of heat from the copper circuit area
on the top surface to an even larger (nearly full coverage) copper
on the flexible bottom heat sink layer, which in turn can be in
thermal communication with a secondary heat sink.
[0210] In one embodiment, at least two high power LEDs are soldered
onto the desired LED receptacles on the top surface of the flexible
layered structure. When electrical current is passed through the
circuit on the top surface of the flexible top conductive layer,
the LEDs facing different directions are energized and emit visible
light. Based on the heat sink structure of the high power LED lamp,
heat generated from the electrical current passed through the LED
is conducted to a heat sink slug on the bottom of the LED. The
efficiency of the LED and corresponding light output performance is
a direct function of the junction temperature ("Tj") of the LED
with heat reducing the efficiency of light production according to
the manufacturer's specifications. The flexible layered structure
of the present invention works to rapidly spread heat away from the
LED heat sink slug proximate the top surface and correspondingly
rapidly conducts heat away from the flexible top conductive layer,
into the bottom electrically isolated copper area, into the
flexible bottom heat sink layer, and optionally to a secondary heat
sink.
[0211] The flexible layered structure is able to efficiently
conduct heat away from LED lights, while at the same time
maintaining the flexible properties of the flexible layered
structure. The rapid spreading of heat away from the LEDs leads to
lower Tj values, higher light output, and higher component
reliability. In one embodiment, another benefit of a flexible,
flexible layered structure of the present disclosure is the further
enhancement of thermal performance due to the ability of a thin
thermally conductive adhesive layer to conform to both the copper
portion of the flexible bottom heat sink layer and the eventual
secondary heat sink. The ability of the flexible, flexible layered
structure to conform to the secondary heat sink allows for improved
intimate thermal contact on curved (and less than perfectly flat)
secondary heat sink surfaces.
LED Light Assemblies
[0212] The flexible layered structures of the present disclosure
can be incorporated into LED lighting assemblies, as follows:
[0213] 1. the flexible layered structure is pulled from a reel or
alternatively, pulled from a stack of panels or sheets;
[0214] 2. the release layer is pulled away, exposing the heat sink
adhesive;
[0215] 3. the heat sink adhesive layer is applied to a secondary
heat sink, either a single heat sink component or a plurality of
heat sink components;
[0216] 4. the heat sink(s) can be configured in their final three
dimensional configuration prior to application of the flexible
layered structure or bent to a particular 3 dimensional
configuration after application of the flexible layered
structure;
[0217] 5. the flexible top conductive layer is circuitized at any
point in the process; and
[0218] 6. the LEDs can be applied to the circuitized flexible top
conductive layer of the flexible layered structure immediately
after circuitization or can be applied further downstream in the
process.
[0219] In some embodiments a LED lighting assembly can be used as a
replacement light for an A19 type light bulb. Other final LED
lighting assemblies that could be adapted in accordance with the
present disclosure and configured sufficient to provide one or more
of the following types of lights:
[0220] 1. cove lights;
[0221] 2. residential overhead lights;
[0222] 3. linear lights;
[0223] 4. rope lights;
[0224] 5. accent lights;
[0225] 6. projector lights;
[0226] 7. stage bar lights;
[0227] 8. par lamp lights;
[0228] 9. linear lights;
[0229] 10. color changer lights;
[0230] 11. display case lights;
[0231] 12. undercabinet lights;
[0232] 13. backdrop lights;
[0233] 14. accent lights;
[0234] 15. refrigerated display case lights;
[0235] 16. hazardous lights;
[0236] 17. industrial fixture lights;
[0237] 18. functional office lights;
[0238] 19. down lights;
[0239] 20. recessed lights;
[0240] 21. roadway lights;
[0241] 22. canopy lights;
[0242] 23. area lights;
[0243] 24. pole top lights;
[0244] 25. solar flood lights;
[0245] 26. lantern lights;
[0246] 27. decorative suspended lights;
[0247] 28. task lights;
[0248] 29. flash light;
[0249] 30. headlamps;
[0250] 31. work lights; and
[0251] 32. exit sign lights.
[0252] The LED lighting assemblies of the present invention may
also be configured to include any of the following types of
replacement bulbs:
[0253] 1. A-lamp bulbs;
[0254] 2. PAR and R-Lamp bulbs;
[0255] 3. MR16 bulbs;
[0256] 4. candelabra bulbs; and
[0257] 5. linear fluorescent bulbs
In some embodiments, the LED lighting assembly has a light bulb
replacement configuration sufficient to be a replacement for one or
more of the following: A-lamp bulbs, PAR-lamp bulbs, R-lamp bulbs,
MR16-lamp bulbs, candelabra lamp bulbs and linear fluorescent
bulbs.
[0258] The flexible layered structure for use with high power light
emitting diode system or secondary heat sink can be fabricated in
any one of a number of ways, such as:
[0259] 1. cold sizing;
[0260] 2. extrusion;
[0261] 3. forging;
[0262] 4. hot metal gas forming;
[0263] 5. powder metallurgy; and
[0264] 6. forming by mechanical force at room temperature, such as:
[0265] a. bending; [0266] b. coining; [0267] c. decambering; [0268]
d. deep drawing; [0269] e. drawing; [0270] f. spinning; [0271] g.
flow turning; [0272] h. raising; [0273] i. roll forming; [0274] j.
roll bending; [0275] k. repousse and chasing; [0276] l. rolling;
[0277] m. rubber pad forming; [0278] n. shearing; [0279] o.
stamping; [0280] p. wheel machining; and [0281] q. the like.
[0282] LED lighting assembly of the present disclosure comprises
[0283] i. a flexible top conductive layer comprising a first
conductive metal, the flexible top conductive layer having a
thickness from 4 to 100 microns; [0284] ii. a flexible bottom heat
sink layer comprising a second conductive metal and the flexible
bottom heat sink layer having a thickness of at least 50 microns;
[0285] iii. a flexible dielectric middle layer comprising a
polymer, the flexible dielectric middle layer having a thickness
from 4 to 100 microns and providing electrical insulation between
the flexible top conductive layer and the flexible bottom heat sink
layer;
[0286] the first conductive metal of the flexible top conductive
layer being the same or different from the second conductive metal
of the flexible bottom heat sink layer;
[0287] said LED lighting assembly having a longitudinal axis and a
plurality of defined positions spaced along the longitudinal axis,
and being bent at least 10 degrees proximate at least one of the
plurality of defined positions spaced along the longitudinal axis
or being twisted relative to the longitudinal axis; and
[0288] wherein at least a portion of the plurality of defined
positions comprise an LED and wherein the LED is in electrical
communication with a circuit.
[0289] In some embodiments, the LED lighting assembly is conformed
to at least a portion of a secondary heat sink and bonded to the
secondary heat sink by at least a portion of a heat sink adhesive
layer.
[0290] In some embodiments, at least 50 weight percent of the
flexible dielectric middle layer is a polyimide derived from at
least 30 mole percent aromatic dianhydride based upon total
dianhydride content of the polyimide and at least 30 mole percent
aromatic diamine based upon total diamine content of the
polyimide.
[0291] In some embodiments, the LED lighting assembly has a
flexible dielectric middle layer comprising 1 to 50 weight percent
thermally conductive filler, the thermally conductive filler
comprising one or more members of the group consisting of carbides,
nitrides, borides and oxides.
[0292] In some embodiments, a method of making an LED lighting
assembly comprises: [0293] a) pulling a flexible layered structure
from a reel or from a stack of panels or sheets, the flexible
layered structure comprising: [0294] i. a flexible top conductive
layer comprising a first conductive metal, the flexible top
conductive layer having a thickness from 4 to 200 microns; [0295]
ii. a flexible bottom heat sink layer comprising a second
conductive metal and the flexible bottom heat sink layer having a
thickness of at least 50 microns; [0296] iii. a flexible dielectric
middle layer comprising a polymer, the flexible dielectric middle
layer having a thickness from 4 to 100 microns and providing
electrical insulation between the flexible top conductive layer and
the flexible bottom heat sink layer; [0297] iv. a heat sink
adhesive layer; and [0298] v. a release liner
[0299] wherein the first conductive metal of the flexible top
conductive layer being the same or different from the second
conductive metal of the flexible bottom heat sink layer, and the
flexible layered structure has a longitudinal axis and a plurality
of defined positions spaced along the longitudinal axis, the
flexible layered structure being bendable at least 10 degrees
proximate at least one of the plurality of defined positions spaced
along the longitudinal axis and the flexible layered structure also
being twistable relative to the longitudinal axis, [0300] b)
removing the release liner thereby exposing a the heat sink
adhesive layer, [0301] c) applying the heat sink adhesive layer to
a secondary heat sink, thereby adhering at least a portion of the
flexible layered structure to the secondary heat sink; [0302] d)
configuring the flexible layered structure with the release liner
removed into a three dimensional configuration and wherein at any
time before, during or after during the above method steps, the
flexible top conductive layer is circuitized and thereafter at
least two LEDs are applied to the flexible top conductive layer of
the flexible layered structure.
[0303] In some embodiments, the flexible layered structure is bent
into a light bulb replacement configuration sufficient for the LED
lighting assembly to be a replacement for one or more of the
following: down lights A-lamp bulbs, PAR-lamp bulbs, R-lamp bulbs,
MR16-lamp bulbs, candelabra lamp bulbs and linear fluorescent
bulbs.
[0304] In some embodiments, the flexible layered structure is bent
into a configuration sufficient to provide one or more of the
following types of lights: [0305] cove lights; [0306] residential
overhead lights; [0307] linear lights; [0308] rope lights; [0309]
accent lights; [0310] projector lights; [0311] stage bar lights;
[0312] par lamp lights; [0313] color changer lights; [0314] display
case lights; [0315] undercabinet lights; [0316] backdrop lights;
[0317] refrigerated display case lights; [0318] hazardous lights;
[0319] industrial fixture lights; [0320] functional office lights;
[0321] down lights; [0322] recessed lights; [0323] roadway lights;
[0324] canopy lights; [0325] area lights; [0326] pole top lights;
[0327] solar flood lights; [0328] lantern lights; [0329] decorative
suspended lights; [0330] task lights; [0331] flash light; [0332]
headlamps; [0333] work lights; and [0334] exit sign lights.
[0335] In some embodiments, additional benefits of the flexible
layered structure are the utility and cost savings of building
reeled, pre-populated, high wattage LED systems. The flexible
layered structure provides a substrate on which surface mounted,
higher wattage LEDs can be mounted and then reeled onto a cored
reel. Reeled continuous linear strips of high wattage LEDs can be
easily handled and applied to secondary heat sinks during
manufacturing assembly.
[0336] The above specification, examples and data provide a
complete description of the manufacture and use of the composition
of the invention. Since many embodiments of the invention can be
made without departing from the spirit and scope of the invention,
the invention resides in the claims hereinafter appended.
* * * * *