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MOLDING COMPOSITION AND METHOD, AND MOLDED ARTICLE
BACKGROUND OF THE INVENTION
Solid state electronic devices are typically encapsulated in plastic via transfer
molding. Encapsulation protects the device from environmental and mechanical
damage and electrically isolates the device. There are many desired technical features
of encapsulant compositions. Encapsulation of wire-bonded devices requires low
viscosity encapsulant injection, followed by rapid cure and hot ejection. In order to
avoid damaging the solid state device, the encapsulant must not shrink excessively on
curing. The encapsulated device must subsequently withstand the rigor of solder
assembly onto a circuit card. The encapsulant must also be self-extinguishing in the
event of a heat-producing malfunction of the circuit. And the encapsulant must
adhere strongly to copper leadframes.
In current epoxy-based encapsulation compositions, it is advantageous to use as much
mineral filler as possible in order to decrease moisture absorption and thermal
expansion of the cured composition. However, higher filler levels are associated with
reduced flow and impaired moldability, which are manifested as poor mold filling and
increased defect generation. There is therefore a need for encapsulation compositions
that exhibit increased flow at high filler loadings.
BRIEF DESCRIPTION OF THE INVENTION
The above-described and other drawbacks are alleviated by a curable composition,
comprising:
an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt; and
a second latent cationic cure catalyst comprising
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a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C 1 -C12)-hydrocarbylsulfonates, (C2-C 12)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(Ci-Ci2)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluororaethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
a cure co-catalyst selected from free-radical generating.aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition.
Other embodiments, including a cured composition, a method of preparing the curable
composition, a method of encapsulating a solid state device, and an encapsulated solid
state device, are described in detail below.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a side cross-sectional view of an encapsulated solid state device.
DETAILED DESCRIPTION OF THE INVENTION
One embodiment is a curable composition, comprising:
an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt; and
a second latent cationic cure catalyst comprising
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a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1-C12)-hydrocarbylsulfonates, (C2-C12)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(C[-Ci2)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition.
In the course of extensive research, the present inventors have discovered that these
curable compositions, when compared to current epoxy-based encapsulation
compositions, exhibit improved spiral flow at a given inorganic filler loading. This
allows improved molding characteristics at constant filler loading, as well as
equivalent molding characteristics at increased filler loading. The increased filler
loadings translate into reduced moisture absorption and reduced thermal expansion in
the cured compositions.
The curable composition comprises an epoxy resin. Suitable types of epoxy resins
include, for example, aliphatic epoxy resins, cycloaliphatic epoxy resins, bisphenol-A
epoxy resins, bisphenol-F epoxy resins, phenol novolac epoxy resins, cresol-novolac
epoxy resins, biphenyl epoxy resins, polyfunctional epoxy resins, naphthalene epoxy
resins, divinylbenzene dioxide, 2-glycidylphenylglycidyl ether, dicyclopentadiene-type
epoxy resins, multi aromatic resin type epoxy resins, and the like, and combinations
thereof.
In one embodiment, a solid epoxy resin is used; i.e., the epoxy resin comprises an
epoxy resin having a softening point of about 25°C to about 150°C. Softening points
may be determined according to ASTM E28-99 (2004). While it is possible to use
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epoxy resins with melting points below 25°C, the amounts of such resins should be
low enough so as not to interfere with the desired friability of the curable composition
as a whole.
In one embodiment, the epoxy resin comprises a monomeric epoxy resin (e.g.,
3,3\5,5'-tetramethyl-4,4'-diglycidyloxybiphenyl, available as RSS1407LC from Yuka
Shell), and an oligomeric epoxy resin (e.g., an epoxidized cresol novolac resin, or a
multi aromatic resin such as Nippon Kayaku's NC3000). Monomeric epoxy resins are
typically crystalline solids, whereas oligomeric epoxy resins are typically glasses.
In one embodiment, the epoxy resin comprises a biphenyl epoxy resin and an
epoxidized ortho-cresol novolac resin.
The amount of epoxy resin in the composition will vary according to the specific use
of the composition and the types and amounts of other components, but it will
typically be about 4 to about 30 weight percent, based on the total weight of the
composition. Within this range, the epoxy amount may be at least about 6 weight
percent, or at least about 8 weight percent. Also within this range, the epoxy amount
may be up to about 20 weight percent, or up to about 15 weight percent.
The curable composition comprises a cure catalyst comprising a first latent cationic
cure catalyst, a second latent cationic cure catalyst, and a cure co-catalyst. The first
latent cationic cure catalyst comprises a diaryl iodonium hexafluoroantimonate salt.
In one embodiment, the diaryl iodonium hexafluoroantimonate salt comprises a diaryl
iodonium cation having the structure
[(R3)(R4)I]+
wherein R3 and R4 are each independently C6-C14 hydrocarbyl, optionally substituted
with from 1 to 4 monovalent radicals selected from C1-C20alkyl, C1-C20 alkoxy, nitro,
and chloro. As used herein, the term "hydrocarbyl", whether used by itself, or as a
prefix, suffix, or fragment of another term, refers to a residue that contains only
carbon and hydrogen. The residue may be aliphatic or aromatic, straight-chain, cyclic,
bicyclic, branched, saturated, or unsaturated. It may also contain combinations of
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aliphatic, aromatic, straight chain, cyclic, bicyclic, branched, saturated, and
unsaturated hydrocarbon moieties. The hydrocarbyl residue, when so stated however,
may contain heteroatoms over and above the carbon and hydrogen members of the
substituent residue. Thus, when specifically noted as containing such heteroatoms,
the hydrocarbyl or hydrocarbylene residue may also contain carbonyl groups, amino
groups, hydroxyl groups, or the like, or it may contain heteroatoms within the
backbone of the hydrocarbyl residue.
In one embodiment, the diaryl iodonium hexafluoroantimonate salt comprises a diaryl
iodonium cation having the structure

wherein each occurrence of p is independently 0 to 19, and each occurrence of q is
independently 0, 1, or 2, with the proviso that at least one occurrence of q is at least 1.
In one embodiment, the diaryl iodonium hexafluoroantimonate salt comprises 4-
octyloxyphenyl phenyl iodonium hexafluoroantimonate.
The cure catalyst comprises a second latent cationic cure catalyst, which in turn
comprises a diaryl iodonium cation, and an anion selected from perchlorate,
unsubstituted and substituted (C1-C12)-hydrocarbylsulfonates, (C2-C12)-
perfluoroalkanoates, tetrafluoroborate, unsubstituted and substituted tetra-(C1-C12)-
hydrocarbylborates, hexafluorophosphate, hexafluoroarsenate, imidodisulfurylfluoride
anion ("N(SO2F)2), tris(trifluoromethylsulfonyl)methyl anion CC(SO2CF3)3),
bis(trifluoromethylsulfonyl)methyl anion CCH(SO2CF3)2),
bis(trifluoromethylsulfuryl)imide anion (~N(SO2CF3)2), and the like, and combinations
thereof.
Suitable unsubstituted and substituted (C1-C12)-hydrocarbylsulfonates include, for
example, alkylsulfonates, such as methanesulfonate, butanesulfonate, octanesulfonate,
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and the like; perfluoroalkylsulfonates, such as trifluoromethylsulfonate (triflate), and
nonafluorobutanesulfonate (nonaflate), perfluorooctanesulfonate, 9,10-
dimethoxyanthracene-2-sulfonate, camphorsulfonate, 7,7-dimethyl-2-
oxobicyclo[2.2.1]heptane-l-methanesulfonate, and the like; arylsulfonates such as 4-
fluorobenzenesulfonate, 4-methylbenzenesulfonate (tosylate), and the like; and
combinations thereof.
Suitable (C2-C12)-perfluoroalkanoates include, for example, trifluoroacetate,
nonafluoropentanoate, and the like; and combinations thereof.
Suitable unsubstituted and substituted tetra-(Ci-Ci2)-hydrocarbylborates include, for
example, tetraarylborates such as tetraphenylborate, tetrakis[2,3,5,6-tetrafluoro-4-
(trifluoromethyl)phenyl]borate, tetrakis(3,5-dichloro-2,4,6-trifluorophenyl)borate,
tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis(pentafluorophenyl)borate, and
the like; and alkylarylborates such as tris(3-fluorophenyl)hexylborate,
butyltriphenylborate, and the like; and combinations thereof.
In one embodiment, the diaryl iodonium cation of the second latent cationic cure
catalyst comprises a diaryl iodonium cation having the structure
[(R3)(R4)I]+
wherein R3 and R4 are each independently C6-C14 hydrocarbyl, optionally substituted
with from 1 to 4 monovalent radicals selected from C1-C20alkyl, C1-C20 alkoxy, nitro,
and chloro.
6
In one embodiment, the diaryl iodonium cation of the second latent cationic cure
catalyst comprises a diaryl iodonium cation having the structure


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wherein each occurrence of p is independently 0 to 19, and each occurrence of q is
independently 0, 1, or 2, with the proviso that at least one occurrence of q is at least 1.
In one embodiment, the diaryl iodonium cation of the second latent cationic cure
catalyst comprises 4-octyloxyphenyi phenyl iodonium cation. In one embodiment, the
anion X" is selected from trifluoromethylsulfonate, nonafluorobutanesulfonate, and
hexafluorophosphate.
The cure catalyst comprises a cure co-catalyst selected from free-radical generating
aromatic compounds, peroxy compounds, copper (II) salts of aliphatic carboxylic
acids, copper (II) salts of aromatic carboxylic acids, copper (II) acetylacetonate, and
the like, and combinations thereof. In one embodiment, the cure co-catalyst
comprises benzopinacole.
In one embodiment, the diaryl iodonium hexafluoroantimonate salt comprises 4-
octyloxyphenyl phenyl iodonium hexafluoroantimonate; and the second latent cationic
cure catalyst comprises 4-octyloxyphenyl phenyl iodonium cation and an anion X"
selected from perchlorate, imidodisulfurylfluoride anion, trifluoromethylsulfonate,
perfluorobutanesulfonate, perfluorooctanesulfonate, 4-fluorobenzenesulfonate, 4-
methylbenzenesulfonate, tetrafluoroborate, tetraphenylborate, tetrakis[2,3,5,6-
tetrafluoro-4-(trifluoromethyl)phenyl]borate, tetrakis(3,5-dichloro-2,4,6-
trifluorophenyl)borate, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate,
tetrakis(pentafluorophenyl)borate, tris(3-fluorophenyl)hexylborate,
butyltriphenylborate, hexafluorophosphate, hexafluoroarsenate, and the like.
In one embodiment, the first latent cationic cure catalyst comprises 4-octyloxyphenyl
phenyl iodonium hexafluoroantimonate; the second latent cationic cure catalyst
comprises 4-octyloxyphenyl phenyl iodonium cation and an anion selected from
trifluoromethylsulfonate, nonafluorobutanesulfonate, and hexafluorophosphate; and
the cure co-catalyst comprises benzopinacole.
In one embodiment, the first latent cationic cure catalyst and the second latent cationic
cure catalyst are both photochemically active in contrast to the cure catalyst mixtures
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described in U.S. Patent No. 6,777,460 B2 to Palazzotto et al, which comprise a
photochemically active salt and a non-photochemically active salt.
The components of the cure catalyst are present in amounts such that the cure catalyst
as a whole is effective to cure the epoxy resin. Specific amounts of the cure catalyst
components will vary depend on the types and amounts of composition components,
but they are generally present in the following amounts. The first latent cure catalyst
is generally present at about 0.2 to about 5 parts by weight per 100 parts by weight of
the epoxy resin. Within the range, the first latent cure catalyst amount may be at least
about 0.3 parts by weight, or at least 0.7 parts by weight. Also within this range, the
first latent cure catalyst amount may be up to about 3 parts by weight, or up to about 2
parts by weight.
The second latent cure catalyst is generally present at about 0.1 to about 3 parts by
weight per 100 parts by weight of the epoxy resin. Within this range, the second
latent cure catalyst amount may be at least about 0.2 parts by weight, or at least about
0.4 parts by weight. Also within this range, the second latent cure catalyst amount
may be up to about 2 parts by weight, or up to about 1 part by weight
The cure co-catalyst is generally present at about 0.2 to about 5 parts by weight per
100 parts by weight of epoxy resin. Within this range, the cure co-catalyst amount
may be at least about 0.3 parts by weight, or at least about 0.7 parts by weight. Also
within this range, the cure co-catalyst amount may be up to about 3 parts by weight, or
up to about 2 parts by weight.
The curable composition comprises about 70 to about 95 weight percent of an
inorganic filler, based on the total weight of the curable composition. In one
embodiment, the inorganic filler is selected from metal oxides, metal nitrides, metal
carbonates, metal hydroxides, and combinations thereof. In one embodiment, the
inorganic filler may be alumina, silica (including fused silica and crystalline silica),
boron nitride (including spherical boron nitride), aluminum nitride, silicon nitride,
magnesia, magnesium silicate, and the like, and combinations thereof. In one
embodiment, the inorganic filler comprises a fused silica. In one embodiment, the
inorganic filler comprises, based on the total weight of inorganic filler, about 75 to
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about 98 weight percent of a first fused silica having an average particle size of 1
micrometer to about 30 micrometers, and about 2 to about 25 weight percent of a
second fused silica having an average particle size of about 0.03 micrometer to less
than 1 micrometer.
The composition may, optionally, further comprise a poly(arylene ether) resin. In one
embodiment, wherein the poly(arylene ether) resin comprises a plurality of repeating
units having the structure

wherein each occurrence of Q2 is independently selected from hydrogen, halogen,
primary or secondary C1-C12 alkyl, C2-C12 alkenyl, C3-C12 alkenylalkyl, C2-C12
alkynyl, C3-C12 alkynylalkyl, C1-C12 hydroxyalkyl, phenyl, Ci-C12 haloalkyl, C1-C12
hydrocarbyloxy, and C2-C12 halohydrocarbyloxy wherein at least two carbon atoms
separate the halogen and oxygen atoms; and wherein each occurrence of Q1 is
independently selected from halogen, primary or secondary C1-C12 alkyl, C2-C12
alkenyl, C3-C12 alkenylalkyl, C2-C12 alkynyl, C3-C12 alkynylalkyl, C1-C12
hydroxyalkyl, phenyl, C1-C12 haloalkyl, C1-C12 hydrocarbyloxy, and C2-C12
halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and
oxygen atoms. Methods of preparing poly(arylene ether) resins are known in the art
and include, for example, U.S. Patent Nos. 3,306,874 and 3,306,875 to Hay.
In one embodiment, the poly(arylene ether) resin has the structure
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wherein each occurrence of Q2 is independently selected from hydrogen, halogen,
primary or secondary C1-C12 alkyl, C2-C12 alkenyl, C3-C12 alkenylalkyl, C2-C12
alkynyl, C3-C12 alkynylalkyl, C1-C12 hydroxyalkyl, phenyl, C1-C12 haloalkyl, C\-Ci2
hydrocarbyloxy, and C2-C12 halohydrocarbyloxy wherein at least two carbon atoms
separate the halogen and oxygen atoms; and wherein each occurrence of Q1 is
independently selected from hydrogen, halogen, primary or secondary C1-C12 alkyl,
C2-C12 alkenyl, C3-C12 alkenylalkyl, C2-C12 alkynyl, C3-C12 alkynylalkyl, C1-C12
hydroxyalkyl, phenyl, C1-C12 haloalkyl, C1-C12 hydrocarbyloxy, and C2-C12
halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and
oxygen atoms; each occurrence of x is independently 1 to about 100; z is 0 or 1; and Y
has a structure selected from

wherein each occurrence of R1 and R2 is independently selected from hydrogen and
C1-C12 hydrocarbyl. Methods for producing these poly(arylene ether) resins,
sometimes called "dihydroxy" or "difunctional" or "bifunctional" poly(arylene ether)
resins are described, for example, in U.S. Patent Nos. 3,496,236 to Cooper et al.,
4,140,675 and 4,165,422 and 4,234,706 to White, 4,521,584 and 4,677,185 to Heitz et
al., 4,562,243 and 4,663,402 and 4,665,137 to Percec, 5,021,543 to Mayska et al.,
5,880,221 to Liska et al., 5,965,663 to Hayase, 6,307,010 Bl to Braat et al., 6,569,982
to Hwang et al., and 6,794,481 to Amagai et al.
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In one embodiment, the poly(arylene ether) resin comprises at least one terminal
functional group selected from carboxylic acid, glycidyl ether, and anhydride.
Poly(arylene ether) resins substituted with terminal carboxylic acid groups and
methods for their preparation are described, for example, in European Patent No.
261,574 Bl to Peters et al. Glycidyl ether-functionalized poly(arylene ether) resins
and methods for their preparation are described, for example, in U.S. Patent Nos.
6,794,481 to Amagai et al. and 6,835,785 to Ishii et al., and U.S. Patent Application
Publication No. 2004/0265595 Al to Tokiwa. Anhydride-functionalized poly(arylene
ether) resins and methods for their preparation are described, for example, in
European Patent No. 261,574 Bl to Peters et al., and U.S. Patent Application
Publication No. 2004/0258852 Al to Ohno et al.
In one embodiment, the poly(arylene ether) has an intrinsic viscosity of about 0.03 to
about 1.0 deciliter per gram measured at 25 °C in chloroform. In one embodiment, the
poly(arylene ether) resin has an intrinsic viscosity of about 0.03 to 0.15 deciliter per
gram measured at 25°C in chloroform.
In one embodiment, the poly(arylene ether) resin comprises less than 5 weight percent
of particles having an equivalent spherical diameter greater than 100 micrometers.
The poly(arylene ether) resin may comprise less than 2 weight percent, or less than 1
weight percent of such particles. The poly(arylene ether) resin may exclude particles
greater than 80 micrometers, or greater than 60 micrometers. Methods of preparing
such poly(arylene ether)s directly or via comminution and size segregation are known
in the art. For example, a poly(arylene ether) resin meeting the particle size limitation
may be prepared directly by controlling precipitation conditions as described, for
example, in U.S. Patent No. 6,787,633 B2 to Peemans et al. As another example, a
poly(arylene ether) resin meeting the particle size limitation may be prepared by
starting with a poly(arylene ether) having greater than 5 weight percent of particles
greater than 100 micrometers, reducing the particle size, e.g., by grinding, and
separating a poly(arylene ether) resin fraction meeting the particle size limitation, e.g.,
by sieving the resin with a 170 mesh (88 micrometer opening) sieve.
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When present, the poly(arylene ether) resin may be used in an amount of about 2 to
about 50 parts by weight of poly(arylene ether) resin per 100 parts by weight of the
epoxy resin. Within this range, the poly(arylene ether) resin amount may be at least
about 5 parts by weight, or at least about 10 parts by weight. Also within this range,
the poly(arylene ether) amount may be up to about 40 parts by weight, or up to about
30 parts by weight.
The curable composition may, optionally, further comprise a low stress additive to
reduce stresses imposed on the solid state device during the curing that follows
encapsulation. Suitable low stress additives include, for example, polybutadienes,
hydrogenated polybutadienes, polyisoprenes, hydrogenated polyisoprenes, butadiene-
styrene copolymers, hydrogenated butadiene-styrene copolymers, butadiene -
acrylonitrile copolymers, hydrogenated butadiene-acrylonitrile copolymers,
polydimethylsiloxanes, poly(dimethysiloxane-co-diphenylsiloxane)s, and
combinations thereof; wherein the low stress additive comprises at least one
functional group selected from hydroxy, carboxylic acid, anhydride, and glycidyl.
Suitable low stress additives thus include, for example, hydroxy-terminated
polybutadienes, carboxy-terminated polybutadienes, maleic anhydride-functionalized
("maleinized") polybutadienes, epoxy-terminated polybutadienes, hydroxy-terminated
hydrogenated polybutadienes, carboxy-terminated hydrogenated polybutadienes,
maleic anhydride-functionalized hydrogenated polybutadienes, epoxy-terminated
hydrogenated polybutadienes, hydroxy-terminated styrene-butadiene copolymers
(including, random, block, and graft copolymers), carboxy-terminated styrene-
butadiene copolymers (including, random, block, and graft copolymers), maleic
anhydride functionalized styrene-butadiene copolymers (including, random, block,
and graft copolymers), epoxy-terminated styrene-butadiene copolymers (including,
random, block, and graft copolymers), butadiene-acrylonitrile copolymers,
hydrogenated butadiene-acrylonitrile copolymers, hydroxy-terminated (i.e., silanol-
terminated) polydimethylsiloxanes, hydrocarbyloxy-terminated (i.e., carbinol-
terminated) polydimethylsiloxanes, carboxy-terminated polydimethylsiloxanes,
anhydride-terminated polydimethylsiloxanes, epoxy-terminated
polydimethylsiloxanes, hydroxy-terminated poly(dimethysiloxane-co-
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diphenylsiloxane)s, carboxy-terminated poly(dimethysiloxane-co-diphenylsiloxane)s,
anhydride-terminated poly(dimethysiloxane-co-diphenylsiloxane)s, epoxy-terminated
poly(dimethysiloxane-co-diphenylsiloxane)s, and the like, and combinations thereof.
These rubbery modifiers and methods for their preparation are known in the art, and
many are commercially available. A suitable amount of rubbery modifier will depend
on the type and amount of epoxy resin and the filler loading, among other factors, but
it is generally about 1 to about 30 parts by weight per 100 parts by weight of the epoxy
resin. Rubbery modifiers may be in the form of finely dispersed particles or reactive
liquids.
The curable composition of claim 1, further comprising an effective amount of a
curing co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof.
The curable composition may, optionally, further comprise an effective amount of a
curing co-catalyst. Suitable curing co-catalysts include, for example, free-radical
generating aromatic compounds (e.g., benzopinacole), copper (II) salts of aliphatic
carboxylic acids (e.g., copper (II) stearate), copper (II) salts of aromatic carboxylic
acids (e.g., copper (II) benzoate, copper (II) naphthenate, and copper (II) salicylate),
copper (II) acetylacetonate, peroxy compounds (e.g., t-butyl peroxybenzoate, 2,5-bis-t-
butylperoxy-2,5-dimethyl-3-hexyne, and other peroxy compounds as described, for
example, in U.S. Patent No. 6,627,704 to Yeager et al.), and the like, and
combinations thereof. In one embodiment, the curing co-catalyst comprises
benzopinacole. In another embodiment, the curing co-catalyst comprises copper (II)
acetylacetonate. A suitable amount of curing co-catalyst will depend on the type of
co-catalyst, the type and amount of epoxy resin, and the type and amount of cure
catalyst, among other factors, but it is generally about 0.01 to about 20 parts by weight
per 100 parts by weight of epoxy resin.
The curable composition may, optionally, further comprise one or more additives
known in the art. Such additives include, for example, phenolic hardeners, anhydride
hardeners, silane coupling agents, flame retardants, mold release agents, colorants
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(including pigments and dyes), thermal stabilizers, adhesion promoters, and
combinations thereof. Those skilled in the art can select suitable additives and
amounts. When phenolic hardeners and/or anhydride hardeners are present, they are
used in an amount such that the primary curing mechanism is epoxy
homopolymerization induced by the cure catalyst.
In one embodiment, the composition is substantially free of polystyrene polymers,
including high impact polystyrenes. Such polystyrene polymers may be defined, for
example, by reference to U.S. Patent No. 6,518,362 to Clough et al.
In one embodiment, the curable composition comprises
an epoxy resin comprising a biphenyl epoxy resin and an epoxidized ortho-cresol
novolac resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising 4-octyloxyphenyl phenyl iodonium
hexafluoroantimonate;
a second latent cationic cure catalyst comprising 4-octyloxyphenyl phenyl iodonium
cation and an anion selected from trifluoromethylsulfonate,
nonafluorobutanesulfonate, and hexafluorophosphate; and
a cure co-catalyst comprising benzopinacole; and
about 70 to about 95 weight percent of a silica filler, based on the total weight of silica
filler; wherein the silica filler comprises about 75 to about 98 weight percent of a first
fused silica having an average particle size of 1 micrometer to about 30 micrometers,
and about 2 to about 25 weight percent of a second fused silica having an average
particle size of about 0.03 micrometer to less than 1 micrometer.
In this embodiment, the composition may, optionally, further comprise about 2 to
about 50 parts by weight of a poly(arylene ether) resin per 100 parts by weight of the
epoxy resin.
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As the composition is defined as comprising multiple components, it will be
understood that each component is chemically distinct, particularly in the instance that
a single chemical compound may satisfy the definition of more than one component.
The invention includes cured compositions obtained on curing the curable
compositions described herein. Thus, one embodiment is a cured composition
comprising the reaction product of a curable composition comprising:
an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt; and
a second latent cationic cure catalyst comprising
a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (Ci-Ci2)-hydrocarbylsulfonates, (C2-Ci2)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(Ci-Ci2)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition.
The invention includes methods of preparing the curable composition. Thus, one
embodiment is a method of preparing a curable composition, comprising
blending
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an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt;
a second latent cationic cure catalyst comprising
a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1-C12)-hydrocarbylsulfonates, (C2-C12)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(C1-C12)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition;
to form an intimate blend.
Another method of preparing a curable composition, comprises:
dry blending
an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt;
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a second latent cationic cure catalyst comprising
a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1-C12)-hydrocarbylsulfonates, (C2-C12)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(Ci-Ci2)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition;
to form a first blend;
melt mixing the first blend at a temperature of about 90 to about 115°C to form a
second blend;
cooling the second blend; and
grinding the cooled second blend to form the curable composition.
The invention includes methods of encapsulating solid state devices using the curable
composition. Thus, one embodiment is a method of encapsulating a solid state
device, comprising:
encapsulating a solid state device with a curable composition comprising
an epoxy resin;
an effective amount of a cure catalyst comprising
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a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt;
a second latent cationic cure catalyst comprising
a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1-C12)-hydrocarbylsulfonates, (C2-C12)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(Ci-Ci2)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition; and
curing the curable composition. Curing the composition may, optionally, include a
post-curing step (e.g., at about 150 to about 190°C for about 0.5 to about 8 hours in a
convection oven).
Suitable methods for encapsulating solid state devices are known in the art and
described, for example, in U.S. Patent Nos. 5,064,882 to Walles, 6,632,892 B2 to
Rubinsztajn et al., 6,800,373 B2 to Gorczyca, 6,878,783 to Yeager et al.; U.S. Patent
Application Publication No. 2004/0166241 Al to Gallo et al.; and International Patent
Application No. WO 03/072628 Al to Dcezawa et al.
The invention further includes encapsulated solid state devices prepared using the
curable composition. Thus, one embodiment is an encapsulated solid state device,
comprising:
a solid state device; and
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a cured composition encapsulating the solid state device, wherein the cured
composition comprises the reaction product obtained on curing a curable composition
comprising
an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt;
a second latent cationic cure catalyst comprising
a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1-C12)-hydrocarbylsulfonates, (C2-C 12)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(Ci-Ci2)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition.
FIG. 1 is a side cross-sectional view of an encapsulated solid state device, 10. The
solid state device 20 is attached to copper leadframe 30 via adhesive layer 40. The
solid state device 10 is electrically connected to the copper leadframe 30 via gold
wires 50 and ground bonds 60. Cured molding compound 70 encapsulates the solid
state device 20, any exposed edges of the adhesive layer 40, gold wires 50, ground
bonds 60, and a portion of the copper lead frame 30, leaving exposed the pad 80,
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corresponding to a surface of the copper leadframe 30 beneath the solid state device
20.
All ranges disclosed herein are inclusive of the endpoints, and the endpoints are
combinable with each other.
The invention is further illustrated by the following non-limiting examples.
GENERAL DESCRIPTION OF EXPERIMENTAL METHODS
Compounds were prepared by mixing the ingredients first in a Henschel mixer, and
then passing them through a twin-screw extruder set at 60°C in the rear section and
90°C in the front. After cooling and hardening, the materials were then ground to a
powder using a Retch mill.
Spiral flow lengths were determined according to ASTM standard D3123-98 (also
SEMI Gll-88), using the standard spiral flow mold specified therein. A 20-gram
charge of the molding compound was transferred into the spiral cavity of the tool, and
the length traveled by the compound before flow stopped due to curing and pressure
drop was measured. The injection speed and injection pressure were kept constant
across all formulations, at 5.84 centimeters/second (2.3 inches/sec) and 6.9
megapascals (MPa), respectively.
Specimens for flexural strength, thermomechanical analysis, and moisture absorption
measurements were prepared by transfer molding as follows. A 15-ton resin transfer
press (Fujiwa) was used. A 4-cavity "Izod" specimen mold was used to transfer-mold
a 35-gram charge of EMC under an injection pressure of 6.9 MPa, at a ram speed of
0.254 millimeters/second (0.1 inches/second). The mold was maintained at 175°C,
and a two minute cure cycle was used. Specimens were post-cured in a forced-air
convection oven for six hours at 175°C.
Thermomechanical analysis (TMA) was used to determine the coefficient of thermal
expansion (CTE) values and the glass transition temperature (Tg) of the molded EMC.
TMA was performed on a Perkin Elmer TMA 7 Instrument. Transfer-molded
specimens measuring at least 3 millimeters in each dimension were used. The sample
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temperature was first ramped at 5°C/min from 25°C to 250°C then cooled at 5°C/min
to 0°C. The second heat, used for analysis, ramped from 0°C at 5°C/min to 25O°C.
An initial vertical probe force of 0,05 Newton was used. The glass transition
temperature, Tg, was taken as the point of intersection of two tangents drawn to the
dimension-temperature curve, at 50°C and 190°C. The measurements were made
under a nitrogen atmosphere at 100 milliliters/minute.
Moisture absorption was determined by measuring the increase in weight of 6.35 cm x
1.25 cm x 0.3 cm (2.5 inch x 0.5 inch x 1/8 inch; standard "Izod" dimensions)
samples after 24 hours in boiling water.
Flexural Strength was determined at room temperature according to ASTM D790 for
three-point bend flexural test using 6.35 cm x 1.27 cm x 0.3175 cm (2.5 inch x 0.5
inch x 1/8 inch) samples.
EXAMPLES 1-4
The compositions detailed in Table 1 were mixed as described above. Examples 1-3
are comparative examples. All component amounts in Table 1 are expressed in parts
by weight. Example 4 is an example of the present invention. "Denka FB570 silica"
is a fused silica obtained from Denka having a median particle size of 17.7
micrometers and a surface area of 3.1 meter/gram. "Denka SFP silica" is a fused
silica obtained from Denka having a median particle size of 0.7 micrometers and a
surface area of 6.2 meters/gram. "Yuka RSS1407LC epoxy", obtained from Yuka
Shell, is 3,3',5,5'-tetramethyl-4,4'-diglycidyloxybiphenyl. "Sumitomo ECN-195XL-
25", obtained from Sumitomo Chemical, is an epoxidized ortho-cresol novolac resin.
"OPPI" is 4-octyloxyphenyl phenyl iodonium hexafluoroantimonate available from
GE Advanced Materials-Silicones as UV9392c. "OPPI O3SC4F9" is 4-
octyloxyphenyl phenyl iodonium nonafluoro-n-butane sulfonate. It was prepared as
follows: 50 grams of 4-octyloxyphenyl phenyl iodonium toluenesulfonate (from GE
Silicones) was stirred with 30 grams of potassium nonafluoro-n-butanesulfonate in
250 milliliters acetone for 2 hours at room temperature; next the mixture was filtered
to remove the potassium toluenesulfonate that had precipitated out of solution; after
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2/3 of the acetone was removed under vacuum, the solution was poured into 1000
milliliters deionized water; this caused the product to precipitate as an orangish solid;
after drying over night in a vacuum oven at 50°C, 57.8 grams of product (95% yield)
was obtained; further purification was achieved by recrystallization from 40 milliliters
toluene plus 160 milliliters hexane; the resulting material was a white solid with a
melting point of 97-98°C. A micronized carnauba wax was obtained as MICHEM®
Wax 411 from Michelman. Carbon black pigment was obtained as BLACK
PEARLS® 120 from Cabot.
Table 1

Ingredient Example1 Example2 Example3 Example4
Denka FB570 Silica 1530 1530 1530 1530
Denka SFP Silica 170 170 170 170
YukaRSS1407LCEpoxy 56.97 56.86 56.59 56.59
Sumitomo ECN-195XL-25 227.89 227.45 226.34 226.34
OPPI 3.42 2.84 4.24 2.83
OPPIO3SC4F9 0 0 0 1.41
Benzopinacole 1.71 2.84 2.83 2.83
Carnauba Wax 6.0 6.0 6.0 6.0
Carbon Black 4.0 4.0 4.0 4.0
Measured property values are presented in Table 2, below. The results show that the
use Example 4, with a mixture of iodonium hexafluoroantimonate and iodonium
perfluorobutane sulfonate salts, exhibited substantially increased spiral flow relative
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to Examples 1-3 with varying levels of the iodonium hexafluoroantimonate alone.
Other properties remained relatively constant.
Table 2

Test Example 1 Example 2 Example 3 Example 4
Spiral Flow (cm) at 175°C 78.5 74.9 76.5 128.0
Spiral Flow (cm) at 165°C 104.9 93.2 101.0 152.9
CTE1 (ppm/°C) 11 12 12 11
CTE2 (ppm/°C) 39 47 39 41
Tg(°C) 148 138 154 154
Moisture Abs. (%) 0.238 0.238 0.266 0.236
Flex Strength (MPa) 129.5 146.1 136.5 131.5
EXAMPLES 5 AND 6
The materials listed in Table 3 were mixed as described above to produce curable
compositions. Example 5 is a comparative example while Example 6 is an example
of the use of the present invention.
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Table 3
Ingredient Example 5 Example 6
Denka FB570 Silica 1575 1429.02
DenkaSFP Silica 175 158.78
Nippon Kayaku NC-3000 Epoxy Resin 235.3 212.44
OPPI 2.35 2.12
OPPIO3SC4F9 0 1.06
Benzopinacole 2.35 2.12
Carnauba Wax 6.0 5.44
Carbon Black 4.0 3.63
Measured property values are presented in Table 4, below. These data once again
demonstrate that increased spiral flows can be achieved with the mixed catalysts.
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Table 4

Test Example 5 Example 6
Spiral Flow (cm) at 175°C 70.6 91.4
Spiral Flow (cm) at 165°C 94.7 112.5
CTE1 (ppm/°C) 10 8.7
CTE2 (ppm/°C) 39 34
Tg(°C) 141 148
Moisture Abs. (%) 0.166 0.209
Flex Strength (MPa) 130.8 127.7
EXAMPLES 7 AND 8
The materials listed in Table 5 were mixed as described above to give curable
compositions. Example 7 is a comparative example at 90% filler loading while
Example 8 is an example of the use of the present invention at the same filler loading.
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Table 5
Ingredient Example 7 Example 8
DenkaFB570 Silica 1620 1620
Denka SFP Silica 180 180
YukaRSS1407LCEpoxy 37.33 37.07
Sumitomo ECN-195XL-25 149.31 148.3
OPPI 2.24 1.85
OPPIO3SC4F9 0 0.93
Benzopinacole 1.12 1.85
Carnauba Wax 6.0 6.0
Carbon Black 4.0 4.0
Measured property values are presented in Table 6, below. Comparing spiral flow
values for Example 5, with a single iodonium catalyst, and Example 6, with an
iodonium catalyst mixture, shows that use of the iodonium catalyst mixture enhances
spiral flow even at very high filler content.
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Table 6
Test Example 5 Example 6
Spiral Flow (cm) at 175°C 41.4 71.4
Spiral Flow (cm) at 165°C 53.8 85.1
CTE1 (ppm/°C) 7 6.1
CTE2 (ppm/°C) 25 28
Tg (°C) 143 152
Moisture Abs. (%) 0.178 0.209
Flex Strength (MPa) 130.4 131.4
EXAMPLES 7 and 8
Molding compounds containing 4-octyloxyphenyl phenyl iodonium
hexafluoroantimonate ("OPPI SbF6") and either 4-octyloxyphenyl phenyl iodonium
triflate ("OPPI CF3SO3'") or 4-octyloxyphenyl phenyl iodonium hexafluorophosphate
("OPPI PF6"") were prepared and tested as described above. Samples of 4-
octyloxyphenyl phenyl iodonium triflate and 4-octyloxyphenyl phenyl iodonium
hexafluorophosphate were obtained from Hampford Research.
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Table 7

Ingredient Example 7 Example 8
Denka FB570 Silica 1530 1530
Denka SFP Silica 170 170
YukaRSS1407LCEpoxy 56.59 56.59
Sumitomo ECN-195XL-25 226.34 226.34
OPPI SbF6" 2.83 2.83
OPPICF3SO3 1.41 0
OPPI PF6" 0 1.41
Benzopinacole 2.83 2.83
Carnauba Wax 6.00 6.00
Carbon Black 4.00 4.00
Measured property values are presented in Table 8, below. Compared to Example 3
above, Examples 7 and 8 exhibited significantly enhanced spiral flow.
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Table 8

Property Example 7 Example 8
Spiral Flow (in) at 175°C 49.4 49.0
Spiral Flow (in) at 165°C Not Tested 58.0
Moisture Abs. (%) 0.187 0.226
Flex Strength (MPa) 139.6 117.1
Cu Tab Pull Adhesion (lbs) 11.3 26.3
While the invention has been described with reference to a preferred embodiment, it
will be understood by those skilled in the art that various changes may be made and
equivalents may be substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to adapt a particular
situation or material to the teachings of the invention without departing from the
essential scope thereof. Therefore, it is intended that the invention not be limited to
the particular embodiment disclosed as the best mode contemplated for carrying out
this invention, but that the invention will include all embodiments falling within the
scope of the appended claims.
All cited patents, patent applications, and other references are incorporated herein by
reference in their entirety.
The use of the terms "a" and "an" and "the" and similar referents in the context of
describing the invention (especially in the context of the following claims) are to be
construed to cover both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. Further, it should further be noted that the terms
"first," "second," and the like herein do not denote any order, quantity, or importance,
but rather are used to distinguish one element from another.
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CLAIMS:
1. A curable composition, comprising:
an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt; and
a second latent cationic cure catalyst comprising
a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1-C12)-hydrocarbylsulfonates, (C2-Ci2)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(Ci-C[2)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (D) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition.
2. The curable composition of claim 1, wherein the epoxy resin comprises an
epoxy resin having a softening point of about 25°C to about 150°C.
3. The curable composition of claim 1, wherein the epoxy resin is selected from
aliphatic epoxy resins, cycloaliphatic epoxy resins, bisphenol-A epoxy resins,
bisphenol-F epoxy resins, phenol novolac epoxy resins, cresol-novolac epoxy resins,
biphenyl epoxy resins, polyfunctional epoxy resins, naphthalene epoxy resins,
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divinylbenzene dioxide, 2-glycidylphenylglycidyl ether, dicyclopentadiene-type epoxy
resins, multi aromatic resin type epoxy resins, and Combinations thereof.
4. The curable composition of claim 1, wherein the epoxy resin comprises a
monomeric epoxy resin and an oligomeric epoxy resin.
5. The curable composition of claim 1, wherein the epoxy resin comprises a
biphenyl epoxy resin and an epoxidized ortho-cresol novolac resin.
6. The curable composition of claim 1, wherein the diaryl iodonium
hexafluoroantimonate salt comprises a diaryl iodonium cation having the structure
[(R3)(R4)I]+
wherein R3 and R4 are each independently C6-C14 hydrocarbyl, optionally substituted
with from 1 to 4 monovalent radicals selected from C1-C20 alkyl, C1-C20 alkoxy, nitro,
and chloro.
7. The curable composition of claim 1, wherein the diaryl iodonium
hexafluoroantimonate salt comprises a diaryl iodonium cation having the structure

wherein each occurrence of p is independently 0 to 19, and each occurrence of q is
independently 0, 1, or 2, with the proviso that at least one occurrence of q is at least 1.
8. The curable composition of claim 1, wherein the diaryl iodonium
hexafluoroantimonate salt comprises 4-octyloxyphenyl phenyl iodonium
hexafluoroantimonate.
9. The curable composition of claim 1, wherein the diaryl iodonium cation of the
second latent cationic cure catalyst comprises a diaryl iodonium cation having the
structure
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[(R3)(R4)I]+
wherein R" and R4 are each independently C6-C14 hydrocarbyl, optionally substituted
with from 1 to 4 monovalent radicals selected from C1-C20alkyl, C1-C20 alkoxy, nitro,
and chloro.
10. The curable composition of claim 1, wherein the diaryl iodonium cation of the
second latent cationic cure catalyst comprises a diaryl iodonium cation having the
structure

wherein each occurrence of p is independently 0 to 19, and each occurrence of q is
independently 0, 1, or 2, with the proviso that at least one occurrence of q is at least 1.
11. The curable composition of claim 1, wherein the diaryl iodonium cation of the
second latent cationic cure catalyst comprises 4-octyloxyphenyl phenyl iodonium
cation.
12. The curable composition of claim 1, wherein the anion X is selected from
trifluoromethylsulfonate, nonafluorobutanesulfonate, and hexafluorophosphate.
13. The curable composition of claim 1, wherein the diaryl iodonium
hexafluoroantimonate salt comprises 4-octyloxyphenyl phenyl iodonium
hexafluoroantimonate; and wherein the second latent cationic cure catalyst comprises
4-octyloxyphenyl phenyl iodonium cation and an anion X selected from perchlorate,
imidodisulfurylfluoride anion, trifluoromethylsulfonate, perfluorobutanesulfonate,
perfluorooctanesulfonate, 4-fluorobenzenesulfonate, 4-methylbenzenesulfonate,
tetrafluoroborate, tetraphenylborate, tetrakis[2,3,5,6-tetrafluoro-4-
(trifluoromethyl)phenyl]borate, tetrakis(3,5-dichloro-2,4,6-trifluorophenyl)borate,
tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis(pentafluorophenyl)borate,
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tris(3-fluorophenyl)hexylborate, butyl triphenylborate, hexafluorophosphate, and
hexafluoroarsenate.
14. The curable composition of claim 1, wherein the cure co-catalyst comprises
benzopinacole.
15. The curable composition of claim 1, wherein the first latent cationic cure
catalyst comprises 4-octyloxyphenyl phenyl iodonium hexafluoroantimonate; wherein
the second latent cationic cure catalyst comprises 4-octyloxyphenyl phenyl iodonium
cation and an anion selected from trifluoromethylsulfonate,
nonafluorobutanesulfonate, and hexafluorophosphate; and wherein the cure co-
catalyst comprises benzopinacole.
16. The curable composition of claim 1, wherein the first latent cationic cure
catalyst and the second latent cationic cure catalyst are photochemically active.
17. The curable composition of claim 1, comprising about 0.2 to about 5 parts by
weight of the first latent cationic cure catalyst, about 0.1 to about 3 parts by weight of
the second latent cationic cure catalyst, and about 0.2 to about 5 parts by weight of the
cure co-catalyst, all based on 100 parts by weight of the epoxy resin.
18. The curable composition of claim 1, wherein the inorganic filler is selected
from metal oxides, metal nitrides, metal carbonates, metal hydroxides, and
combinations thereof.
19. The curable composition of claim 1, wherein the inorganic filler is selected
from alumina, silica [including fused silica and crystalline silica], boron nitride
[including spherical boron nitride], aluminum nitride, silicon nitride, magnesia,
magnesium silicate, and combinations thereof.
20. The curable composition of claim 1, wherein the inorganic filler comprises a
fused silica.
21. The curable composition of claim 1, wherein the inorganic filler comprises,
based on the total weight of inorganic filler, about 75 to about 98 weight percent of a
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first fused silica having an average particle size of 1 micrometer to about 30
micrometers, and about 2 to about 25 weight percent of a second fused silica having
an average particle size of about 0.03 micrometer to less than 1 micrometer.
22. The curable composition of claim 1, further comprising a poly(arylene ether)
resin.
23. The curable composition of claim 20, wherein the poly(arylene ether) resin
comprises a plurality of repeating units having the structure

wherein each occurrence of Q2 is independently selected from hydrogen, halogen,
primary or secondary C1-C12 alkyl, C2-C12 alkenyl, C3-C12 alkenylalkyl, C2-C12
alkynyl, C3-C12 alkynylalkyl, C1-C12 hydroxyalkyl, phenyl, C1-C12 haloalkyl, C1-C12
hydrocarbyloxy, and C2-C12 halohydrocarbyloxy wherein at least two carbon atoms
separate the halogen and oxygen atoms; and wherein each occurrence of Q1 is
independently selected from halogen, primary or secondary C1-C12 alkyl, C2-C12
alkenyl, C3-C12 alkenylalkyl, C2-C12 alkynyl, C3-C12 alkynylalkyl, C1-Ci2
hydroxyalkyl, phenyl, C1-C12 haloalkyl, C1-C12 hydrocarbyloxy, and C2-C12
halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and
oxygen atoms.
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24. The curable composition of claim 20, wherein the poly(arylene ether) resin has
the structure

wherein each occurrence of Q2 is independently selected from hydrogen, halogen,
primary or secondary C1-C12 alkyl, C2-C12 alkenyl, C3-C12 alkenylalkyl, C2-C12
alkynyl, C3-C12 alkynylalkyl, C1-C12 hydroxyalkyl, phenyl, C1-C12 haloalkyl, C1-C12
hydrocarbyloxy, and C2-C12 halohydrocarbyloxy wherein at least two carbon atoms
separate the halogen and oxygen atoms; and wherein each occurrence of Q1 is
independently selected from hydrogen, halogen, primary or secondary C1-C12 alkyl,
C2-C12 alkenyl, C3-C12 alkenylalkyl, C2-C12 alkynyl, C3-C12 alkynylalkyl, CrC12
hydroxyalkyl, phenyl, C1-C12 haloalkyl, C1-C12 hydrocarbyloxy, and C2-C12
halohydrocarbyloxy wherein at least two carbon atoms separate the halogen and
oxygen atoms; each occurrence of x is independently 1 to about 100; z is 0 or 1; and Y
has a structure selected from

wherein each occurrence of R1 and R2 is independently selected from hydrogen and
C1-C12 hydrocarbyl.
25. The curable composition of claim 20, wherein the poly(arylene ether) resin
comprises at least one terminal functional group selected from carboxylic acid,
glycidyl ether, and anhydride.
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26. The curable composition of claim 20, wherein the poly(arylene ether) has an
intrinsic viscosity of about 0.03 to about 1.0 deciliter per gram measured at 25°C in
chloroform.
27. The curable composition of claim 20, wherein the poly(arylene ether) resin has
an intrinsic viscosity of about 0.03 to 0.15 deciliter per gram measured at 25°C in
chloroform.
28. The curable composition of claim 20, wherein the poly(arylene ether) resin
comprises less than 5 weight percent of particles greater than 100 micrometers
29. The curable composition of claim 1, further comprising a low stress additive
selected from polybutadienes, hydrogenated polybutadienes, polyisoprenes,
hydrogenated polyisoprenes, butadiene-styrene copolymers, hydrogenated butadiene-
styrene copolymers, butadiene-acrylonitrile copolymers, hydrogenated butadiene-
acrylonitrile copolymers, polydimethylsiloxanes, poly(dimethysiloxane-co-
diphenylsiloxane)s, and combinations thereof; wherein the low stress additive
comprises at least one functional group selected from hydroxy, hydrocarbyloxy, vinyl
ether, carboxylic acid, anhydride, and glycidyl.
30. The curable composition of claim 1, further comprising an effective amount of
a curing co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof.
31. The curable composition of claim 1, further comprising an additive selected
from phenolic hardeners, anhydride hardeners, silane coupling agents, flame
retardants, mold release agents, colorants, thermal stabilizers, adhesion promoters, and
combinations thereof.
32. The curable composition of claim 1, wherein the composition is substantially
free of polystyrene polymers.
33. A curable composition, comprising:
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an epoxy resin comprising a biphenyl epoxy resin and an epoxidized ortho-cresol
novolac resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising 4-octyloxyphenyl phenyl iodonium
hexafluoroantimonate;
a second latent cationic cure catalyst comprising 4-octyloxyphenyl phenyl iodonium
cation and an anion selected from trifluoromethylsulfonate,
nonafluorobutanesulfonate, and hexafluorophosphate; and
a cure co-catalyst comprising benzopinacole; and
about 70 to about 95 weight percent of a silica filler, based on the total weight of silica
filler; wherein the silica filler comprises about 75 to about 98 weight percent of a first
fused silica having an average particle size of 1 micrometer to about 30 micrometers,
and about 2 to about 25 weight percent of a second fused silica having an average
particle size of about 0.03 micrometer to less than 1 micrometer.
34. The curable composition of claim 30, further comprising about 2 to about 50
parts by weight of a poly(arylene ether) resin per 100 parts by weight of the epoxy
resin.
35. A cured composition comprising the reaction product of a curable composition
comprising:
an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt; and
a second latent cationic cure catalyst comprising
a diaryl iodonium cation, and
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an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1-C12)-hydrocarbylsulfonates, (C7-C12)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(Cj-Ci2)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion and
combinations thereof; and
a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (H) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition.
36. A method of preparing a curable composition, comprising
blending
an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt;
a second latent cationic cure catalyst comprising
a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1-C12)-hydrocarbylsulfonates, (C2-C12)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(Ci-Ci2)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
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a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate. and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition;
to form an intimate blend.
37. A method of preparing a curable composition, comprising:
dry blending
an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt;
a second latent cationic cure catalyst comprising
a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1-C12)-hydrocarbylsulfonates, (C2-C12)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(C1-C12)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition;
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to form a first blend;
melt mixing the first blend at a temperature of about 90 to about 115°C to form a
second blend;
cooling the second blend; and
grinding the cooled second blend to form the curable composition.
38. A method of encapsulating a solid state device, comprising:
encapsulating a solid state device with a curable composition comprising
an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt;
a second latent cationic cure catalyst comprising
a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1-C12)-hydrocarbylsulfonates, (C2-C12)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(C1-C12)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition; and
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curing the curable composition.
39. An encapsulated solid state device, comprising:
a solid state device; and
a cured composition encapsulating the solid state device, wherein the cured
composition comprises the products obtained on curing a curable composition
comprising
an epoxy resin;
an effective amount of a cure catalyst comprising
a first latent cationic cure catalyst comprising a diaryl iodonium hexafluoroantimonate
salt;
a second latent cationic cure catalyst comprising
a diaryl iodonium cation, and
an anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1 -C12)-hydrocarbylsulfonates, (C2-C12)-perfluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(C1-C12)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and
a cure co-catalyst selected from free-radical generating aromatic compounds, peroxy
compounds, copper (II) salts of aliphatic carboxylic acids, copper (II) salts of aromatic
carboxylic acids, copper (II) acetylacetonate, and combinations thereof; and
about 70 to about 95 weight percent of an inorganic filler, based on the total weight of
the curable composition.

A curable method useful for encapsulating solid state devices includes (A) an epoxy
resin; (B) an effective amount of a cure catalyst comprising (Bl) a first latent cationic
cure catalyst comprising a diaryl iodonium hexafluoroantimonate salt; (B2) a second
latent cationic cure catalyst comprising (B2a) a diaryl iodonium cation, and (B2b) an
anion selected from perchlorate, imidodisulfurylfluoride anion, unsubstituted and
substituted (C1-C12)-hydrocarbylsulfonates, (C2-C12)-peifluoroalkanoates,
tetrafluoroborate, unsubstituted and substituted tetra-(C1-C12)-hydrocarbylborates,
hexafluorophosphate, hexafluoroarsenate, tris(trifluoromethylsulfonyl)methyl anion,
bis(trifluoromethylsulfonyl)methyl anion, bis(trifluoromethylsulfuryl)imide anion, and
combinations thereof; and (B3) a cure co-catalyst selected from free-radical generating
aromatic compounds, peroxy compounds, copper (II) salts of aliphatic carboxylic
acids, copper (II) salts of aromatic carboxylic acids, copper (II) acetylacetonate, and
combinations thereof; and (C) about 70 to about 95 weight percent of an inorganic
filler, based on the total weight of the curable composition. The composition's cure
catalyst allows the use of increased filler loadings, which in turn reduces moisture
absorption and thermal expansion of the cured composition.