U.S. patent application number 17/009263 was filed with the patent office on 2020-12-17 for silicone-modified epoxy resin composition and semiconductor device.
This patent application is currently assigned to Shin-Etsu Chemical Co., Ltd.. The applicant listed for this patent is Shin-Etsu Chemical Co., Ltd.. Invention is credited to Norifumi KAWAMURA, Shoichi OSADA, Kohei OTAKE.
Application Number | 20200392340 17/009263 |
Document ID | / |
Family ID | 1000005063077 |
Filed Date | 2020-12-17 |
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United States Patent
Application |
20200392340 |
Kind Code |
A1 |
KAWAMURA; Norifumi ; et
al. |
December 17, 2020 |
SILICONE-MODIFIED EPOXY RESIN COMPOSITION AND SEMICONDUCTOR
DEVICE
Abstract
The invention provides a resin composition comprising a specific
silicone-modified epoxy resin, a specific silicone-modified
phenolic resin, black pigment, and an inorganic filler. The
invention also provides a resin composition comprising a specific
cyanate ester compound, a specific silicone-modified epoxy resin,
and a specific phenol compound and/or silicone-modified phenolic
resin.
Inventors: |
KAWAMURA; Norifumi;
(Annaka-shi, JP) ; OSADA; Shoichi; (Annaka-shi,
JP) ; OTAKE; Kohei; (Annaka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shin-Etsu Chemical Co., Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Shin-Etsu Chemical Co.,
Ltd.
Tokyo
JP
|
Family ID: |
1000005063077 |
Appl. No.: |
17/009263 |
Filed: |
September 1, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15971019 |
May 4, 2018 |
|
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17009263 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08G 77/388 20130101;
C08G 59/1494 20130101; C08K 5/0041 20130101; C08G 77/42 20130101;
C08G 59/4028 20130101; C08G 59/306 20130101; C08G 59/1433 20130101;
C08G 59/3281 20130101; C08G 59/62 20130101; C08G 77/80 20130101;
C08L 83/06 20130101; C08G 77/14 20130101; C08L 83/10 20130101; C08G
59/4085 20130101; C08L 2203/20 20130101; C08G 77/38 20130101 |
International
Class: |
C08L 83/10 20060101
C08L083/10; C08K 5/00 20060101 C08K005/00; C08G 59/14 20060101
C08G059/14; C08G 59/40 20060101 C08G059/40; C08L 83/06 20060101
C08L083/06; C08G 59/32 20060101 C08G059/32; C08G 59/62 20060101
C08G059/62; C08G 59/30 20060101 C08G059/30 |
Foreign Application Data
Date |
Code |
Application Number |
May 19, 2017 |
JP |
2017-099972 |
May 19, 2017 |
JP |
2017-100000 |
Claims
1. A silicone-modified epoxy resin composition comprising: (P) a
cyanate ester compound having at least two cyanato groups per
molecule, (A) a silicone-modified epoxy resin obtained from
hydrosilylation reaction of an alkenyl-containing epoxy compound
with an organopolysiloxane having the average compositional formula
(1): H.sub.aR.sub.bSiO.sub.(4-a-b)/2 (1) wherein R is each
independently a C.sub.1-C.sub.10 monovalent hydrocarbon group, a is
a positive number: 0.01.ltoreq.a.ltoreq.1, b is a positive number:
1.ltoreq.b.ltoreq.3, meeting 1.01.ltoreq.a+b<4, and (F) a phenol
compound having at least two phenolic hydroxyl groups per molecule
and/or a silicone-modified phenolic resin obtained from
hydrosilylation reaction of an alkenyl-containing phenol compound
with an organopolysiloxane having the average compositional formula
(1), wherein a molar ratio of epoxy groups in the epoxy resin (A)
to cyanato groups in the cyanate ester compound (P) is in the range
of 0.04 to 0.30, and a molar ratio of phenolic hydroxyl groups in
the phenol compound (F) to cyanato groups in the cyanate ester
compound (P) is in the range of 0.08 to 0.30.
2. The silicone-modified epoxy resin composition of claim 1 wherein
component (P) is a compound having the general formula (2):
##STR00030## wherein R.sup.1 and R.sup.2 are each independently
hydrogen or C.sub.1-C.sub.4 alkyl, R.sup.3 is each independently a
divalent group selected from the following formulae: ##STR00031##
wherein R.sup.4 is each independently hydrogen or methyl, and n is
an integer of 0 to 10.
3. The silicone-modified epoxy resin composition of claim 1 wherein
the organopolysiloxane in components (A) and (F) is at least one
member selected from compounds having the formulae (a), (b) and
(c): ##STR00032## wherein R is as defined above, R.sup.1 is
hydrogen or a group as defined for R, n.sup.1 is an integer of 0 to
200, n.sup.2 is an integer of 0 to 2, n.sup.3 is an integer of 0 to
10, with the proviso that n', n.sup.2 and n.sup.3 are not equal to
0 at the same time, and R.sup.2 is a group having the formula (a'):
##STR00033## wherein R and R.sup.1 are as defined above, n.sup.4 is
an integer of 1 to 10, siloxane units each in brackets may be
randomly bonded or form blocks, the compound of formula (a)
containing at least one silicon-bonded hydrogen per molecule,
##STR00034## wherein R is as defined above, n.sup.5 is an integer
of 0 to 10, n.sup.6 is an integer of 1 to 4, meeting
3.ltoreq.n.sup.5+n.sup.6.ltoreq.12, the arrangement of siloxane
units each in brackets is not limited, ##STR00035## wherein R and
R.sup.1 are as defined above, r is an integer of 0 to 3, and
R.sup.7 is hydrogen or a C.sub.1-C.sub.10 organic group, the
compound of formula (c) containing at least one silicon-bonded
hydrogen per molecule.
4. The silicone-modified epoxy resin composition of claim 1 wherein
the alkenyl-containing phenol compound in component (F) has the
following formula ##STR00036##
5. A semiconductor device encapsulated with a cured product of the
silicone-modified epoxy resin composition of claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a Divisional of copending application
Ser. No. 15/971,019 filed on May 4, 2018, which claims priority
under 35 U.S.C. .sctn. 119(a) on Patent Application Nos.
2017-099972 and 2017-100000 filed in Japan on May 19, 2017 and May
19, 2017, respectively, the entire contents of which are hereby
incorporated by reference.
TECHNICAL FIELD
[0002] This invention relates to a silicone-modified epoxy resin
composition having improved tracking resistance, a
silicone-modified epoxy resin composition having a reduced modulus
and the suppressed risk of cracks and separation while maintaining
thermal stability and temperature/humidity resistance, and a
semiconductor device encapsulated with a cured product of the resin
composition.
BACKGROUND ART
[0003] The current mainstream of semiconductor devices including
diodes, transistors, ICs, and LSIs is of the resin encapsulation
type. Epoxy resins have superior moldability, adhesion, electrical
properties, mechanical properties, and moisture resistance to other
thermosetting resins. It is thus widely spread to encapsulate
semiconductor devices with epoxy resin compositions. Over the
decade, the electronic equipment market is under the increasing
trend toward compact size, light weight and high performance of
semiconductor devices and high integration of semiconductor chips.
Since the spacing between interconnects or wires within the
semiconductor is accordingly reduced, the resin composition is
required to have higher reliability.
[0004] As a result of reduction of size and profile, the width of
circuit pitch and the distance between lead terminals are reduced.
This makes it difficult to secure a space distance and creepage
distance sufficient to provide electric insulation therebetween.
For the encapsulant as the insulator, improvements in performance,
especially tracking resistance are required.
[0005] In the prior art, several means for enhancing tracking
resistance of encapsulants such as epoxy resin compositions are
known. For example, Patent Document 1 proposes to increase the
amount of inorganic filler blended, Patent Document 2 describes to
blend a small amount of silicone rubber powder in addition to an
inorganic filler, Patent Document 3 discloses a mixture of an
alicyclic epoxy resin having a cyclohexane polyether skeleton, but
free of a benzene skeleton susceptible to formation of conductive
paths and a dicyclopentadiene type phenolic resin, and Patent
Document 4 describes the use of an aminotriazine-modified novolak
resin or melamine resin as curing agent. On the other hand, the
progress is toward semiconductor chips of thin profile and wires of
reduced size, suggesting that flow during molding is an important
factor. Increasing the amount of inorganic filler blended is
effective for the purpose of enhancing tracking resistance at the
sacrifice of flow during molding. Also, while aromatic moiety makes
a substantial contribution to the heat resistance of resin
compositions, non-aromatic epoxy resins invite a lowering of heat
resistance, giving detrimental impact on reliability.
[0006] In the decade, the semiconductor devices encounter
outstanding technical innovations. For example, the
through-silicon-via (TSV) technology is used in mobile
information/communication terminals such as smart phones and
tablets so that a large volume of data may be processed at a higher
speed. In this technology, semiconductor chips are connected in
multiple layers, and flip-chip connected to silicon interposers of
8 to 12 inches. Thereafter, the silicon interposers having a
plurality of multilayer connected semiconductor chips mounted
thereon are encapsulated with a thermosetting resin. The
unnecessary resin on the semiconductor chips is polished away,
followed by singulation into semiconductor devices with advantages
of small size, thin profile, multi-function, and
high-speed-processing. However, when encapsulation is made by
coating the thermosetting resin on the entire surface of a thin
silicon interposer of 8 to 12 inches, substantial warpage occurs
due to the difference in coefficient of thermal expansion between
the silicon and the thermosetting resin. The substantial warpage
poses an outstanding technical problem because of prohibited
transfer to the subsequent polishing and singulation steps.
[0007] Also over the decades, the environmental countermeasures on
the global level as typified by the energy conversion from fossil
fuel are on progress. In the automobile field, for example, the
number of hybrid cars and electric vehicles manufactured is
increasing. In emerging countries including China and India, an
increasing number of household electric equipment having inverter
motors mounted therein as the energy saving countermeasure are
marketed.
[0008] For hybrid cars, electric vehicles, and inverter motors,
power semiconductor devices for AC/DC or DC/AC conversion and
voltage transformation are important. Although silicon (Si) has
long been used as the semiconductor, the silicon technology
approaches its performance limit. For example, it becomes rather
difficult to expect an outstanding performance improvement such as
a reduction of the resistance of power MOSFET for the purpose of
reducing the power loss during power transformation. Attention is
now paid to power semiconductor devices of the next generation
using wide bandgap semiconductors such as silicon carbide (SiC),
gallium nitride (GaN) and diamond. Among others, the development of
low-loss power MOSFETs using SiC is advancing.
[0009] The wide-gap semiconductors including SiC and GaN have
excellent characteristics as demonstrated by a bandgap of about 3
folds and a breakdown field strength of at least 10 folds greater
than Si. Also reported are such characteristics as high-temperature
operation (operation at 650.degree. C. is reported for SiC), high
thermal conductivity (SiC is equivalent to Cu), and a high
saturation electron drift velocity. By virtue of these
characteristics, the use of SiC or GaN enables to reduce the ON
resistance of power semiconductor devices and to substantially save
the power loss of power conversion circuits.
[0010] Power semiconductor devices are generally protected by
transfer molding of epoxy resin or potting encapsulation of
silicone gel. Recently, from the standpoint of size and weight
reduction (particularly in the automobile application), transfer
molding of epoxy resin becomes the mainstream. Although the epoxy
resin is a thermosetting resin having a good balance of
moldability, substrate adhesion and mechanical strength, it
undergoes pyrolysis of crosslinking points at temperatures in
excess of 200.degree. C. This prohibits the use of epoxy resin as
the encapsulant in the high-temperature environment in which
operation of SiC and GaN devices is expected.
[0011] Then, thermosetting resin compositions containing cyanate
resins are studied as the material having improved thermal
properties. Among the materials having improved thermal properties,
the cyanate resins have a very low coefficient of thermal expansion
and are effective for suppressing shrinkage stress during
encapsulation and curing. Even when large diameter or thin profile
wafers or large-size metal or other substrates are encapsulated,
the cyanate resins are effective for suppressing the warpage of
wafers or substrates.
[0012] For example, Patent Document 5 describes that stable heat
resistance is achieved by reacting a polyfunctional cyanate ester
with an epoxy resin to form an oxazole ring in a cured product of a
phenol novolak resin. It is described therein that a cured product
having improved heat resistance and water resistance is obtained
when the equivalent amount of hydroxyl groups in the phenol novolak
resin is 0.4 to 1.0 and the equivalent amount of cyanato groups in
the polyfunctional cyanate ester is 0.1 to 0.6 per equivalent of
epoxy groups in the epoxy resin. This composition, however, suffers
from poor mass productivity because the reaction of epoxy groups
with cyanato groups to form an oxazole ring requires a high
temperature/long term heat curing step.
[0013] Patent Document 6 describes that a thermosetting resin
composition comprising a cyanate ester compound of specific
structure, a phenol compound, and an inorganic filler has improved
heat resistance and high mechanical strength. Because of
insufficient humidity resistance, the composition has the problem
that peeling and cracking occur when it is held in a hot humid
environment for a long term.
[0014] Patent Document 7 describes that a cured product having
improved thermal stability and temperature/humidity resistance is
obtained from a composition comprising a cyanate ester compound, a
phenol compound, and an epoxy resin of specific structure wherein a
proportion of the phenol compound relative to the cyanate ester
compound and a proportion of the epoxy resin relative to the
cyanate ester compound are controlled to specific ranges. However,
this resin composition has a high modulus and is insufficient in
suppressing separation at the interface between a chip-mounted
surface of a substrate and the cured product of the resin
composition.
[0015] Since cracking in packages and separation at the interface
between a chip-mounted substrate surface and a cured resin
composition are considered problems, stress lowering, that is,
reducing the modulus of a cured product is desired as the means for
preventing these problems.
CITATION LIST
[0016] Patent Document 1: JP-A 2008-143950 [0017] Patent Document
2: JP-A 2013-203865 [0018] Patent Document 3: JP-A 2005-213299
[0019] Patent Document 4: JP-A 2010-031126 [0020] Patent Document
5: JP-B H06-15603 [0021] Patent Document 6: JP-A 2013-053218 [0022]
Patent Document 7: JP-A 2016-210907
DISCLOSURE OF INVENTION
[0023] An object of the invention is to provide a silicone-modified
epoxy resin composition having improved tracking resistance and a
semiconductor device encapsulated with the resin composition.
Another object is to provide a silicone-modified epoxy resin
composition having a reduced modulus and suppressed cracking and
separation while maintaining thermal stability and
temperature/humidity resistance, and a semiconductor device.
[0024] The inventors have found that the outstanding problems are
solved by a silicone-modified epoxy resin composition comprising a
specific silicone-modified epoxy resin, a specific
silicone-modified phenolic resin, a black pigment, and an inorganic
filler.
[0025] A first embodiment of the invention is a silicone-modified
epoxy resin composition comprising:
[0026] (A) a silicone-modified epoxy resin obtained from
hydrosilylation reaction of an alkenyl-containing epoxy compound
with an organopolysiloxane having the average compositional formula
(1):
H.sub.aR.sub.bSiO.sub.(4-a-b)/2 (1)
wherein R is each independently a C.sub.1-C.sub.10 monovalent
hydrocarbon group, a is a positive number: 0.01.ltoreq.a.ltoreq.1,
b is a positive number: 1.ltoreq.b.ltoreq.3, meeting
1.01.ltoreq.a+b<4,
[0027] (B) a silicone-modified phenolic resin obtained from
hydrosilylation reaction of an alkenyl-containing phenol compound
with an organopolysiloxane having the average compositional formula
(1),
[0028] (C) a black pigment, and
[0029] (D) an inorganic filler exclusive of the black pigment
(C).
[0030] In a preferred embodiment, the organopolysiloxane in
components (A) and (B) is at least one member selected from
compounds having the formulae (a), (b) and (c):
##STR00001##
wherein R is as defined above, R.sup.1 is hydrogen or a group as
defined for R, n.sup.1 is an integer of 0 to 200, n.sup.2 is an
integer of 0 to 2, n.sup.3 is an integer of 0 to 10, with the
proviso that n.sup.1, n.sup.2 and n.sup.3 are not equal to 0 at the
same time, and R.sup.2 is a group having the formula (a'):
##STR00002##
wherein R and R.sup.1 are as defined above, n.sup.4 is an integer
of 1 to 10, siloxane units each in brackets may be randomly bonded
or form blocks, the compound of formula (a) containing at least one
silicon-bonded hydrogen per molecule,
##STR00003##
wherein R is as defined above, n.sup.5 is an integer of 0 to 10,
n.sup.6 is an integer of 1 to 4, meeting
3.ltoreq.n.sup.5+n.sup.6.ltoreq.12, the arrangement of siloxane
units each in brackets is not limited,
##STR00004##
wherein R and R.sup.1 are as defined above, r is an integer of 0 to
3, and R.sup.7 is hydrogen or a C.sub.1-C.sub.10 organic group, the
compound of formula (c) containing at least one silicon-bonded
hydrogen per molecule.
[0031] In a preferred embodiment, the alkenyl-containing phenol
compound in component (B) has the following formula.
##STR00005##
[0032] In a preferred embodiment, the inorganic filler (D) is
present in an amount of 150 to 1,500 parts by weight per 100 parts
by weight of components (A) and (B) combined and 60 to 94% by
weight of the total weight of the composition.
[0033] Also contemplated herein is a semiconductor device
encapsulated with a cured product of the silicone-modified epoxy
resin composition defined above.
[0034] The inventors have also found that a resin composition
comprising a specific cyanate ester compound, a specific
silicone-modified epoxy resin, and a specific phenol compound
and/or silicone-modified phenolic resin, wherein a proportion of
the phenol compound relative to the cyanate ester compound and a
proportion of the epoxy resin relative to the cyanate ester
compound are controlled to specific ranges is reduced in modulus
while maintaining thermal stability and thus effective for
suppressing cracks and separation.
[0035] A second embodiment of the invention is a silicone-modified
epoxy resin composition comprising:
[0036] (P) a cyanate ester compound having at least two cyanato
groups per molecule,
[0037] (A) a silicone-modified epoxy resin obtained from
hydrosilylation reaction of an alkenyl-containing epoxy compound
with an organopolysiloxane having the average compositional formula
(1):
H.sub.aR.sub.bSiO.sub.(4-a-b)/2 (1)
wherein R, a, and b are as defined above, and
[0038] (F) a phenol compound having at least two phenolic hydroxyl
groups per molecule and/or a silicone-modified phenolic resin
obtained from hydrosilylation reaction of an alkenyl-containing
phenol compound with an organopolysiloxane having the average
compositional formula (1),
[0039] wherein a molar ratio of epoxy groups in the epoxy resin (A)
to cyanato groups in the cyanate ester compound (P) is in the range
of 0.04 to 0.30, and a molar ratio of phenolic hydroxyl groups in
the phenol compound (F) to cyanato groups in the cyanate ester
compound (P) is in the range of 0.08 to 0.30.
[0040] In a preferred embodiment, component (P) is a compound
having the general formula (2):
##STR00006##
wherein R.sup.1 and R.sup.2 are each independently hydrogen or
C.sub.1-C.sub.4 alkyl, R.sup.3 is each independently a divalent
group selected from the following formulae:
##STR00007##
wherein R.sup.4 is each independently hydrogen or methyl, and n is
an integer of 0 to 10.
[0041] In a preferred embodiment, the organopolysiloxane in
components (A) and (F) is at least one member selected from
compounds having the formulae (a), (b) and (c) defined above.
[0042] In a preferred embodiment, the alkenyl-containing phenol
compound in component (F) has the following formula.
##STR00008##
[0043] Also contemplated herein is a semiconductor device
encapsulated with a cured product of the silicone-modified epoxy
resin composition defined above.
Advantageous Effects of Invention
[0044] The resin composition in the first embodiment of the
invention is advantageous in that using a specific
silicone-modified epoxy resin and a specific silicone-modified
phenolic resin as curing agent, formation of carbide conductive
paths which can cause short-circuiting is suppressed and tracking
resistance is enhanced. The resin composition in the second
embodiment of the invention is advantageous in that using a
specific silicone-modified epoxy resin and a specific phenol
compound and/or silicone-modified phenolic resin as curing agent,
the modulus is reduced and the risk of cracking or separation is
suppressed while maintaining thermal stability and
temperature/humidity resistance.
BRIEF DESCRIPTION OF DRAWINGS
[0045] The only FIGURE, FIG. 1 is a diagram for illustrating how to
determine the Tg of resin compositions of Examples 4 to 7 and
Comparative Examples 4, 5 in the second embodiment of the
invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0046] The notation (Cn-Cm) means a group containing from n to m
carbon atoms per group.
First Embodiment
[0047] The first embodiment of the invention is a resin composition
comprising:
[0048] (A) a silicone-modified epoxy resin obtained from
hydrosilylation reaction of an alkenyl-containing epoxy compound
with an organopolysiloxane having the average compositional formula
(1),
[0049] (B) a silicone-modified phenolic resin obtained from
hydrosilylation reaction of an alkenyl-containing phenol compound
with an organopolysiloxane having the average compositional formula
(1),
[0050] (C) a black pigment, and
[0051] (D) an inorganic filler exclusive of the black pigment
(C).
(A) Silicone-Modified Epoxy Resin
[0052] Component (A) is a copolymer obtained from hydrosilylation
reaction of an alkenyl-containing epoxy compound with a
hydrogenorganopolysiloxane having the average compositional formula
(1). The inclusion of the copolymer ensures that the resin
composition of the first embodiment has high heat resistance,
hygroscopicity, tracking resistance, and flow.
[0053] The alkenyl-containing epoxy compound used herein is not
particularly limited as long as it has epoxy and alkenyl groups and
is generally used in semiconductor encapsulating resin
compositions.
[0054] Suitable epoxy resins include cresol novolak type epoxy
resins, biphenyl type epoxy resins, dicyclopentadiene-modified
phenol type epoxy resins, biphenyl aralkyl type epoxy resins,
triphenylalkane type epoxy resins, naphthol type epoxy resins,
triazine derivative epoxy resins, and epoxycyclohexyl type epoxy
resins. Such epoxy resins further having alkenyl groups such as
vinyl or allyl are useful.
[0055] Of the foregoing epoxy compounds, compounds of the following
structural formulae are preferred because of effective working and
tracking resistance.
##STR00009##
[0056] The hydrogenorganopolysiloxane has the average compositional
formula (1):
H.sub.aR.sub.bSiO.sub.(4-a-b)/2 (1)
wherein R is each independently a C.sub.1-C.sub.10 monovalent
hydrocarbon group, a is a positive number: 0.01.ltoreq.a.ltoreq.1,
b is a positive number: 1.ltoreq.b.ltoreq.3, meeting
1.01.ltoreq.a+b<4.
[0057] Specifically, the hydrogenorganopolysiloxane of formula (1)
has at least one SiH group, preferably 2 to 10 SiH groups per
molecule. In formula (1), R is a C.sub.1-C.sub.10, preferably
C.sub.1-C.sub.6, monovalent hydrocarbon group, examples of which
include alkyl groups such as methyl, ethyl, propyl, isopropyl,
butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, octyl,
nonyl, and decyl, aryl groups such as phenyl, tolyl, xylyl and
naphthyl, and aralkyl groups such as benzyl, phenylethyl, and
phenylpropyl. Inter alia, methyl, ethyl and phenyl are preferred.
Also useful are substituted forms of the hydrocarbon groups in
which some hydrogen is substituted by halogen such as fluorine,
bromine or chlorine.
[0058] The organopolysiloxane having the average compositional
formula (1) may be linear, cyclic or branched. For example, those
having the following formulae (a), (b) and (c) are included.
##STR00010##
[0059] In formula (a), R is as defined above, R.sup.1 is hydrogen
or a group as defined for R, and R.sup.2 is a group having the
formula (a').
##STR00011##
[0060] In formula (a'), R and R.sup.1 are as defined above, n.sup.4
is an integer of 0 to 10, preferably 0 to 2.
[0061] In formula (a), n.sup.1 is an integer of 0 to 200,
preferably 0 to 20; n.sup.2 is an integer of 0 to 2, preferably 0
or 1; n.sup.3 is an integer of 0 to 10, preferably 0 to 6; with the
proviso that n.sup.1, n.sup.2 and n.sup.3 are not equal to 0 at the
same time. Notably, siloxane units each in brackets [ ] may be
randomly bonded or form blocks. The compound of formula (a)
contains at least one silicon-bonded hydrogen (SiH group) per
molecule, preferably 2 to 10 SiH groups per molecule. Then in
formula (a) wherein n.sup.2=0, at least one R.sup.1 in formulae (a)
and (a') is hydrogen.
##STR00012##
[0062] In formula (b), R is as defined above, n.sup.5 is an integer
of 0 to 10, preferably 0 to 6, n.sup.6 is an integer of 1 to 4,
preferably 2 to 4, meeting 3.ltoreq.n.sup.5+n.sup.6.ltoreq.12. The
arrangement of siloxane units each in brackets is not limited.
##STR00013##
[0063] In formula (c), R and R.sup.1 are as defined above, r is an
integer of 0 to 3, and R.sup.7 is hydrogen or a C.sub.1-C.sub.10,
preferably C.sub.1-C.sub.6 organic group, typically monovalent
hydrocarbon group. The compound of formula (c) contains at least
one silicon-bonded hydrogen per molecule. Then in formula (c)
wherein r=0, at least one R.sup.1 is hydrogen.
[0064] Examples of the group R.sup.7 include hydrogen, alkyl groups
such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl,
tert-butyl, pentyl, neopentyl, hexyl, octyl, nonyl, and decyl,
alkoxy groups such as methoxy, ethoxy, propoxy, isopropoxy, butoxy,
isobutoxy, and tert-butoxy, aryl groups such as phenyl, tolyl,
xylyl and naphthyl, and aralkyl groups such as benzyl, phenylethyl,
and phenylpropyl. Inter alia, hydrogen, methyl and phenyl are
preferred.
[0065] Of the hydrogenorganopolysiloxanes, both end
hydrogenmethylpolysiloxanes and both end
hydrogenmethylphenylpolysiloxanes are preferred. For example, the
compounds shown below are preferred.
##STR00014##
[0066] Herein n is an integer of 1 to 100.
##STR00015##
[0067] The hydrosilylation reaction for forming the
silicone-modified epoxy resin as component (A) may accord with any
prior art well-known techniques. For example, the reaction may be
carried out by heating in the presence of a platinum base catalyst
such as chloroplatinic acid. The hydrosilylation reaction is
typically carried out in an inert solvent such as benzene or
toluene at an elevated temperature of 60 to 120.degree. C. A
proportion of the epoxy compound and the polysiloxane is such that
the number of SiH groups on the polysiloxane per alkenyl group on
the epoxy compound may be at least 1.0, preferably 1.5 to 5.0.
(B) Silicone-Modified Phenolic Resin
[0068] Component (B) is a silicone-modified phenolic resin serving
as a curing agent by reacting with epoxy groups. It is a copolymer
obtained from hydrosilylation reaction of an alkenyl-containing
phenol compound with an organopolysiloxane having the average
compositional formula (1) defined above. The inclusion of the
copolymer ensures that the resin composition of the first
embodiment has high heat resistance, hygroscopicity, tracking
resistance, and flow.
[0069] The alkenyl-containing phenol compound used herein is not
particularly limited as long as it has phenolic hydroxyl and
alkenyl groups and is generally used in semiconductor encapsulating
resin compositions. Suitable phenolic resin base curing agents
include phenol novolak resins, cresol novolak resins, phenol
aralkyl resins, biphenyl aralkyl resins, bisphenol A type resins,
bisphenol F type resins, dicyclopentadiene type phenolic resins,
silicone-modified phenolic resins, and triphenolalkane type resins.
Such phenolic resins further having alkenyl groups such as vinyl or
allyl are useful.
[0070] Of the phenol compounds, the compound of the following
structural formula is preferred because of effective working and
tracking resistance.
##STR00016##
[0071] The hydrogenorganopolysiloxane to be reacted with the
alkenyl-containing phenol compound may be of the same structure as
exemplified for the polysiloxane used in component (A).
[0072] The hydrosilylation reaction for forming the
silicone-modified phenolic resin as component (B) may accord with
any prior art well-known techniques. For example, the reaction may
be carried out by heating in the presence of a platinum base
catalyst such as chloroplatinic acid. The hydrosilylation reaction
is typically carried out in an inert solvent such as benzene or
toluene at an elevated temperature of 60 to 120.degree. C. A
proportion of the phenol compound and the polysiloxane is such that
the number of SiH groups on the polysiloxane per alkenyl group on
the phenol compound may be at least 1.0, preferably 1.5 to 5.0.
[0073] The silicone-modified epoxy resin (A) as base and the
silicone-modified phenolic resin (B) as curing agent are preferably
combined such that a ratio of epoxy groups to phenolic hydroxyl
groups ranges from 0.6/1 to 1.6/1, more preferably from 0.8 to
1.3.
(C) Black Pigment
[0074] Component (C) is a black pigment for coloring the resin
composition black. Examples of the pigment used herein include, but
are not limited to, carbon black, furnace black and acetylene black
as used in conventional encapsulating resin compositions. Inter
alia, carbon black is preferred. Now that the resin composition is
colored black, semiconductor devices fabricated using the
composition as semiconductor encapsulant are given satisfactory
outer appearance and laser marking performance comparable to those
of semiconductor devices encapsulated with prior art epoxy resin
compositions.
[0075] The pigment is blended in an amount of preferably at least 1
part by weight, more preferably at least 3 parts by weight per 100
parts by weight of the total of resin components, i.e., components
(A) and (B) in the resin composition. At least 1 pbw of the pigment
is preferred in that luster does not become too high, the outer
appearance fault that a trace of a semiconductor chip reflects on
the semiconductor package surface is avoided, the color is fully
black, and laser marking performance is satisfactory. The amount of
the pigment is preferably up to 10 parts by weight.
(D) Inorganic Filler
[0076] Component (D) is an inorganic filler. Suitable fillers
include silicas such as fused silica, crystalline silica, and
cristobalite, as well as alumina, silicon nitride, aluminum
nitride, boron nitride, titanium oxide, glass fibers, magnesium
oxide, and zinc oxide. Notably, the black pigment as component (C)
is excluded.
[0077] Although the inorganic filler is not particularly limited in
size and shape, the filler preferably has an average particle size
of 1 to 50 .mu.m, more preferably 4 to 20 .mu.m. It is noted that
the average particle size is a value of laser diffraction particle
size distribution measurement such as by Cilas.RTM..
[0078] The inorganic filler preferably has a chloride ion content
of up to 10 ppm, more preferably up to 5 ppm and a sodium ion
content of up to 10 ppm, more preferably up to 5 ppm, when
impurities are extracted from the filler in a concentration of
sample 10 g/water 50 g under conditions: 125.degree. C., 2.1 atm.,
and 20 hours. As long as the impurity content is within the range,
there is no risk that the semiconductor device encapsulated with
the filled composition undergoes a decline of humidity
resistance.
[0079] The inorganic filler is blended in an amount of preferably
150 to 1,500 parts by weight, more preferably 250 to 1,200 parts by
weight per 100 parts by weight of the total of components (A) and
(B). Also preferably the inorganic filler accounts for 60 to 94% by
weight, more preferably 70 to 92% by weight, even more preferably
75 to 90% by weight of the total weight of the resin
composition.
[0080] Prior to use, the inorganic filler is preferably surface
treated with coupling agents for enhancing the bond strength
between the resin component and the filler. Suitable coupling
agents are silane coupling agents and titanate coupling agents.
Preferred are silane coupling agents including epoxy silanes such
as .gamma.-glycidoxypropyltrimethoxysilane,
.gamma.-glycidoxypropylmethyldiethoxysilane,
.beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane;
N-.beta.-(aminoethyl)-.gamma.-aminopropyltrimethoxysilane, the
reaction product of imidazole with
.gamma.-glycidoxypropyltrimethoxysilane; aminosilanes such as
.gamma.-aminopropyltriethoxysilane,
N-phenyl-.gamma.-aminopropyltrimethoxysilane; mercaptosilanes such
as .gamma.-mercaptosilane and
.gamma.-episulfidoxypropyltrimethoxysilane. The amount of the
coupling agent used and the surface treatment mode are not
particularly limited and may accord with the standard
technology.
Second Embodiment
[0081] The second embodiment of the invention is a resin
composition comprising:
[0082] (P) a cyanate ester compound having at least two cyanato
groups per molecule,
[0083] (A) a silicone-modified epoxy resin obtained from
hydrosilylation reaction of an alkenyl-containing epoxy compound
with an organopolysiloxane having the average compositional formula
(1), and
[0084] (F) a phenol compound having at least two phenolic hydroxyl
groups per molecule and/or a silicone-modified phenolic resin
obtained from hydrosilylation reaction of an alkenyl-containing
phenol compound with an organopolysiloxane having the average
compositional formula (1).
(P) Cyanate Ester Compound
[0085] Component (P) is a cyanate ester compound having at least
two cyanato groups per molecule. Any well-known cyanate may be used
as long as it has at least two cyanato groups per molecule. For
example, cyanate ester compounds having the general formula (2) are
useful.
##STR00017##
Herein R.sup.1 and R.sup.2 are each independently hydrogen or
C.sub.1-C.sub.4 alkyl, R.sup.3 is each independently a divalent
group selected from the following formulae:
##STR00018##
wherein R.sup.4 is each independently hydrogen or methyl, and n is
an integer of 0 to 10.
[0086] Examples of the cyanate ester compound (P) include
bis(4-cyanatophenyl)methane, bis(3-methyl-4-cyanatophenyl)methane,
bis(3-ethyl-4-cyanatophenyl)methane,
bis(3,5-dimethyl-4-cyanatophenyl)methane,
1,1-bis(4-cyanotophenyl)ethane, 2,2-bis(4-cyanotophenyl)propane,
2,2-bis(4-cyanotophenyl)-1,1,1,3,3,3-hexafluoropropane,
di(4-cyanotophenyl)thioether, 1,3-dicyanatobenzene,
1,4-dicyanatobenzene, 2-tert-butyl-1,4-dicyanatobenzene,
2,4-dimethyl-1,3-dicyanatobenzene,
2,5-di-tert-butyl-1,4-dicyanatobenzene,
tetramethyl-1,4-dicyanatobenzene, 1,3,5-tricyanatobenzene,
2,2'-dicyanatobiphenyl, 4,4'-dicyanatobiphenyl,
3,3',5,5'-tetramethyl-4,4'-dicyanatobiphenyl,
1,3-dicyanatonaphthalene, 1,4-dicyanatonaphthalene,
1,5-dicyanatonaphthalene, 1,6-dicyanatonaphthalene,
1,8-dicyanatonaphthalene, 2,6-dicyanatonaphthalene,
2,7-dicyanatonaphthalene, 1,3,6-tricyanatonaphthalene;
1,1,1-tris(4-cyanatophenyl)ethane, bis(4-cyanatophenyl) ether,
4,4'-(1,3-phenylenediisopropylidene)diphenyl cyanate,
bis(4-cyanatophenyl) thioether, bis(4-cyanatophenyl) sulfone,
tris(4-cyanatophenyl) phosphine, tris(4-cyanatophenyl) phosphate,
phenol novolak type cyanates, cresol novolak type cyanates,
dicyclopentadiene novolak type cyanates, phenyl aralkyl type
cyanate esters, biphenyl aralkyl type cyanate esters, and
naphthalene aralkyl type cyanate esters, which may be used alone or
in admixture.
[0087] The cyanate ester compound may be obtained by reacting a
phenol with cyanogen chloride under basic conditions. Depending on
a particular application, an appropriate cyanate ester compound may
be selected from a wide variety of compounds covering from solid
one having a softening point of 106.degree. C. to those which are
liquid at normal temperature. For example, when it is desired to
prepare a liquid resin composition, a cyanate ester compound which
is liquid at normal temperature is used. When the epoxy resin
composition is dissolved in a solvent to form a varnish, a choice
may be made depending on solubility and solution viscosity. When a
power semiconductor device is encapsulated with the resin
composition by transfer molding, a cyanate ester compound which is
solid at normal temperature is chosen.
[0088] Also, a cyanate ester compound having a low cyanato group
equivalent, i.e., low molecular weight between functional groups
undergoes less cure shrinkage, so that a cured product having low
thermal expansion and a high glass transition temperature (Tg) is
obtainable. On use of a cyanate ester compound having a high
cyanato group equivalent, triazine crosslink spacing becomes
flexible, despite a little drop of Tg, from which low modulus, high
toughness, and low water absorption are expectable. The cyanate
ester compound may have chlorine bonded thereto or left therein,
preferably in a content of up to 50 ppm, more preferably up to 20
ppm. If the chlorine content exceeds 50 ppm, there is a possibility
that when the cured composition is held at high temperature for a
long time, chlorine or chloride ions are liberated via pyrolysis
and cause corrosion to oxidized Cu frames, Cu wires or Ag plating,
inviting separation of the cured composition or electric failures.
Also chlorine may make the resin less insulating.
[0089] The cyanate ester compound (P) is preferably blended in an
amount of 40 to 80 parts by weight, more preferably 50 to 76 parts
by weight per 100 parts by weight of the total of resin components,
i.e., components (P), (A) and (F).
(A) Silicone-Modified Epoxy Resin
[0090] Component (A) is a copolymer obtained from hydrosilylation
reaction of an alkenyl-containing epoxy compound with a
hydrogenorganopolysiloxane having the average compositional formula
(1). The copolymer is effective for providing the resin composition
of the second embodiment with a low modulus.
[0091] Although the detail of the silicone-modified epoxy resin (A)
is the same as component (A) in the resin composition of the first
embodiment, supplemental reference may be made to the
following.
[0092] While the epoxy resin reacts with the cyanate ester compound
to form an oxazole ring, the rate of this reaction is slow as
compared with the triazine ring-forming reaction of cyanato groups.
Notably a higher proportion of epoxy groups is detrimental to
transfer molding because of a longer curing time. A tertiary amine
such as triethylamine can be used herein, but at the sacrifice of
shelf stability.
[0093] The epoxy resin (A) is blended in such an amount that an
equivalent amount of epoxy groups is 0.04 to 0.30 mole per mole of
cyanato groups in the cyanate ester compound (P). If the amount of
the epoxy resin is below the range, a cured product of the resin
composition of the second embodiment absorbs a more amount of
moisture, with the risk of separation between the lead frame and
the cured product in a hot humid environment. If the amount of the
epoxy resin is beyond the range, the resin composition of the
second embodiment under-cures so that the cured product may have a
low Tg and lose hot-humid-storage stability.
(F) Phenol Compound and/or Silicone-Modified Phenolic Resin
[0094] In one embodiment, component (F) is a phenol compound having
at least two phenolic hydroxyl groups per molecule. Any of
well-known phenol compounds may be used as long as it has at least
two phenolic hydroxyl groups per molecule. Typically the phenol
compound has the general formula (3).
##STR00019##
[0095] Herein R.sup.5 and R.sup.6 are each independently hydrogen
or C.sub.1-C.sub.4 alkyl, R.sup.7 is each independently a group
selected from the following:
##STR00020##
wherein R.sup.4 is each independently hydrogen or methyl, and m is
an integer of 0 to 10.
[0096] Examples of the phenol compound having formula (3) include
bisphenol F type resins, bisphenol A type resins, phenol novolak
resins, phenol aralkyl resins, biphenyl aralkyl resins, and
naphthalene aralkyl resins, which may be used alone or in
admixture.
[0097] In another embodiment, component (F) is a silicone-modified
phenolic resin. It is a copolymer obtained from hydrosilylation
reaction of an alkenyl-containing phenol compound with a
hydrogenorganopolysiloxane having the average compositional formula
(1). The copolymer is effective for providing the resin composition
of the second embodiment with a low modulus.
[0098] Although the detail of the silicone-modified phenolic resin
as component (F) is the same as component (B) in the resin
composition of the first embodiment, supplemental reference may be
made to the following.
[0099] In the prior art, metal salts and metal complexes are used
as the curing catalyst for cyanate ester compounds (see JP-A
S64-43527, JP-A H11-106480, JP-A 2005-506422). Specifically, salts
and complexes of transition metals are used. The transition metals
have a potential to promote oxidative degradation of organic resins
at elevated temperature. In the resin composition of the second
embodiment, the phenol compound functions as a catalyst for
cyclization reaction of the cyanate ester compound. This eliminates
a need for the metal salts and complexes, achieving an improvement
in long-term storage stability at elevated temperature.
[0100] The phenol compound having at least two hydroxyl groups per
molecule is expected to serve as a crosslinker for connecting
triazine rings. Unlike epoxy compounds and amine compounds, the
phenol compound bonds with the cyanate ester compound to form a
structure: --C--O--Ar--. Since this structure is analogous to the
triazine ring structure which is formed when the cyanate ester
compound is cured alone, it is expected that the cured product is
further improved in heat resistance.
[0101] It is noted that a phenol compound having a low hydroxyl
equivalent, for example, a hydroxyl equivalent of up to 110 is
highly reactive with cyanate groups. This means that when a
composition is prepared by melt kneading components at a
temperature of up to 120.degree. C., curing reaction can take place
to invite a substantial loss of flow, which is detrimental to
transfer molding. It is thus desired that the phenol compound have
a hydroxyl equivalent of at least 111.
[0102] The phenol compound is blended in such an amount that 0.08
to 0.30 mole of phenolic hydroxyl groups is available per mole of
cyanato groups. If the amount of the phenol compound blended is
below the range, reaction of cyanato groups is insufficient, with
some cyanato groups being left unreacted. Residual cyanato groups
are hydrolyzed in a humid atmosphere. This suggests that when the
cured product is held in a hot humid environment, a lowering of
mechanical strength and a loss of adhesion to the substrate can
occur. If the amount of the phenol compound blended exceeds the
range, curing reaction can take place at a lower temperature, which
detracts from the flow and moldability of the resin
composition.
[0103] Desirably the phenol compound has a content of halogen or
alkali metal of up to 10 ppm, more desirably up to 5 ppm, when
extracted at 120.degree. C. and 2 atmospheres.
(E) Other Components
[0104] In addition to the essential components described above, the
resin compositions of the first and second embodiments may further
contain various additives such as cure accelerators, parting
agents, flame retardants, ion trapping agents, antioxidants, and
tackifiers, if necessary.
[0105] The cure accelerator is not particularly limited as long as
it can accelerate curing reaction. Suitable cure accelerators
include phosphorus compounds such as triphenylphosphine,
tributylphosphine, tri(p-methylphenyl)phosphine,
tri(p-nonylphenyl)phosphine, triphenylphosphine-triphenylboran,
tetraphenylphosphine tetraphenylborate, tetraphenylphosphine
tetra(p-methylphenyl)borate, and the adduct of triphenylphosphine
and p-benzoquinone; tertiary amine compounds such as triethylamine,
benzyldimethylamine, .alpha.-methylbenzyldimethylamine, and
1,8-diazabicyclo[5.4.0]undecene-7; and imidazole compounds such as
2-methylimidazole, 7-phenylimidazole, and
2-phenyl-4-methylimidazole, which may be used alone or in
admixture. The cure accelerators may also be used in modified
forms, for example, porous silica impregnated with the cure
accelerator and the cure accelerator coated with a thermoplastic
resin such as polymethyl methacrylate. Inter alia, an imidazole
compound having high basicity which is coated with a thermoplastic
resin is preferred. The cure accelerator may be used in an
effective amount, which is preferably 0.1 to 5 parts by weight,
more preferably 0.5 to 2 parts by weight per 100 parts by weight of
the total of essential components in each resin composition, but
not limited thereto.
[0106] Any desired well-known parting agents may be used. Suitable
parting agents include natural wax base parting agents such as
carnauba wax, rice wax, candelilla wax; synthetic high molecular
weight parting agents such as polyethylene, polyethylene oxide,
polypropylene; fatty acid derivative base parting agents such as
lauric acid, stearic acid, palmitic acid, behenic acid, cerotic
acid, montanic acid, stearates, stearamides, ethylene
bis(stearamide); and ethylene-vinyl acetate copolymers. The parting
agents may be used alone or in admixture. The parting agent is
preferably used in an amount of 0.5 to 5 parts by weight, more
preferably 1 to 3 parts by weight per 100 parts by weight of the
total of essential components in each resin composition.
[0107] Any desired well-known flame retardants may be used.
Suitable flame retardants include phosphazene compounds, silicone
compounds, zinc molybdate-carrying talc, zinc molybdate-carrying
zinc oxide, aluminum hydroxide, magnesium hydroxide, molybdenum
oxide, and antimony trioxide. The flame retardant is preferably
used in an amount of 2 to 20 parts by weight, more preferably 3 to
10 parts by weight per 100 parts by weight of the total of
essential components in each resin composition.
[0108] Any desired well-known ion trapping agents may be used.
Suitable ion trapping agents include hydrotalcites, bismuth
hydroxide, and rare earth oxides. The ion trapping agent is
preferably used in an amount of 1 to 10 parts by weight, more
preferably 1.5 to 5 parts by weight per 100 parts by weight of the
total of essential components in each resin composition.
[0109] Any desired well-known tackifiers may be used. For example,
coupling agents as used for the surface treatment of inorganic
fillers may be used as the tackifier. The tackifier may be used
alone or in admixture. The tackifier is preferably used in an
amount of 0.2 to 5 parts by weight, more preferably 0.5 to 3 parts
by weight per 100 parts by weight of the total of essential
components in each resin composition.
[0110] The resin compositions of the first and second embodiments
may be prepared by any desired methods. For example, the resin
composition may be obtained by stirring, dissolving, mixing and
dispersing essential components simultaneously or separately, while
heat treating if necessary, and in some cases, by further adding
optional components to the mixture, mixing, stirring and dispersing
them. Although the machine used in the mixing step is not
particularly limited, suitable machines include an automated
mortar, two-roll mill, three-roll mill, ball mill, continuous
extruder, planetary mixer, and MassColloider, equipped with
stirring and heating units. These machines may be used in a
suitable combination if desired.
[0111] The resin compositions of the first and second embodiments
are useful as an encapsulant for semiconductor devices including
transistor, module, DIP, SO, flat pack and ball grid array type
devices. The method for encapsulating a semiconductor device with
the resin composition is not particularly limited, and any of prior
art molding methods such as transfer molding, injection molding and
casting may be used. The resin composition is preferably molded
under suitable conditions, typically at 160 to 190.degree. C. for
45 to 300 seconds and post-cured at 170 to 250.degree. C. for 2 to
16 hours.
EXAMPLE
[0112] Examples of the invention are given below by way of
illustration and not by way of limitation.
Resin Composition of First Embodiment
Examples 1 to 3
[0113] Resin compositions were prepared by combining components (A)
and (B) synthesized in Synthesis Examples 1 to 5 and the components
shown below in accordance with the formulation described in Table
1, melt mixing them on a hot two-roll mill until uniform, cooling
and grinding.
(A) Silicone-Modified Epoxy Resins E-01, E-02, E-03
Synthesis Example 1
[0114] A 1-L separable flask was charged with 0.16 g of a 0.5 wt %
chloroplatinic acid toluene solution, 80 g of toluene, and 323 g of
monoallyldiglycidylisocyanuric acid (MA-DGIC by Shikoku Chemicals
Corp.), followed by stirring and heating at an internal temperature
of 80.degree. C. Thereafter, 81 g of 1,1,3,3-tetramethyldisiloxane
(Shin-Etsu Chemical Co., Ltd.) was added dropwise over 30 minutes,
and reaction run at 90.degree. C. for 4 hours. The resulting
toluene solution was distilled under reduced pressure, obtaining a
silicone-modified epoxy resin E-01 having a structure of the
formula (4) shown below. The resin E-01 had an epoxy equivalent of
169 g/eq.
##STR00021##
Synthesis Example 2
[0115] A 1-L separable flask was charged with 0.16 g of a 0.5 wt %
chloroplatinic acid toluene solution, 80 g of toluene, and 296 g of
o-allylphenyl glycidyl ether (OAP-EP by Shikoku Chemicals Corp.),
followed by stirring and heating at an internal temperature of
80.degree. C. Thereafter, 110 g of 1,1,3,3-tetramethyldisiloxane
(Shin-Etsu Chemical Co., Ltd.) was added dropwise over 30 minutes,
and reaction run at 90.degree. C. for 4 hours. The resulting
toluene solution was distilled under reduced pressure, obtaining a
silicone-modified epoxy resin E-02 having a structure of the
formula (5) shown below. The resin E-02 had an epoxy equivalent of
257 g/eq.
##STR00022##
Synthesis Example 3
[0116] A 2-L separable flask was charged with 1.68 g of a 0.5 wt %
chloroplatinic acid toluene solution, 200 g of toluene, and 596.06
g (2.4 mol) of 1,2-epoxy-4-vinylcyclohexane, followed by stirring
and heating at an internal temperature of 80.degree. C. Thereafter,
240.51 g (1 mol) of 2,4,6,8-tetramethylcyclotetrasiloxane was added
dropwise over 1 hour, and reaction run at 100.degree. C. for 2
hours. The resulting toluene solution was distilled under reduced
pressure, obtaining a silicone-modified epoxy resin E-03 having a
structure of the formula (6) shown below. The resin E-03 had an
epoxy equivalent of 200 g/eq.
##STR00023##
(B) Silicone-Modified Phenolic Resins P-01, P-02
Synthesis Example 4
[0117] A 1-L separable flask was charged with 0.16 g of a 0.5 wt %
chloroplatinic acid toluene solution, 80 g of toluene, and 263 g of
2-allylphenol (Yokkaichi Chemical Co., Ltd.), followed by stirring
and heating at an internal temperature of 80.degree. C. Thereafter,
124 g of 2,4,6,8-tetramethylcyclotetrasiloxane (KF-9902 by
Shin-Etsu Chemical Co., Ltd.) was added dropwise over 30 minutes,
and reaction run at 90.degree. C. for 3 hours. The resulting
toluene solution was distilled under reduced pressure, obtaining a
silicone-modified phenolic resin P-01 having a structure of the
formula (7) shown below. The resin P-01 had a hydroxyl equivalent
of 194 g/eq.
##STR00024##
Synthesis Example 5
[0118] A 1-L separable flask was charged with 0.16 g of a 0.5 wt %
chloroplatinic acid toluene solution, 80 g of toluene, and 266 g of
2-allylphenol (Yokkaichi Chemical Co., Ltd.), followed by stirring
and heating at an internal temperature of 80.degree. C. Thereafter,
140 g of 1,1,3,3-tetramethyldisiloxane (HM-H by Shin-Etsu Chemical
Co., Ltd.) was added dropwise over 30 minutes, and reaction run at
90.degree. C. for 3 hours. The resulting toluene solution was
distilled under reduced pressure, obtaining a silicone-modified
phenolic resin P-02 having a structure of the formula (8) shown
below. The resin P-02 had a hydroxyl equivalent of 201 g/eq.
##STR00025##
(C) Black Pigment
[0119] carbon black (3230MJ by Mitsubishi Chemical Corp.)
(D) Inorganic Filler
[0120] fused silica powder (average particle size 16 .mu.m, by
Tatsumori Ltd.)
(E) Other Components
Cure Accelerator
[0121] triphenyl phosphine (TPP.RTM. by Hokkou Chemical Co.,
Ltd.)
[0122] 2-ethyl-4-methylimidazole (Curezol.RTM. 2E4MZ by Shikoku
Chemicals Corp.)
Other Additives
[0123] carnauba wax (TOWAX-131 by Toa Kasei Co., Ltd.)
[0124] Silane coupling agent which is a 1:5 mixture of
3-mercaptopropyltrimethoxysilane (KBM-803 by Shin-Etsu Chemical
Co., Ltd.) and 3-glycidoxypropyltrimethoxysilane (KBM-403 by
Shin-Etsu Chemical Co., Ltd.)
Comparative Examples 1 to 3
[0125] Resin compositions were prepared by combining the components
used in Examples 1 to 3 and the epoxy resin and phenolic resin
shown below in accordance with the formulation described in Table
1, melt mixing them on a hot two-roll mill until uniform, cooling
and grinding.
Epoxy Resin
[0126] polyfunctional epoxy resin (EPPN-501H by Nippon Kayaku Co.,
Ltd.)
Phenolic Resin
[0127] phenol novolak resin (TD-2131 by DIC Corp.)
[0128] The thus obtained resin compositions were evaluated by the
following tests.
[Tests]
Tracking Resistance
[0129] The resin composition was molded into a specimen of 50 mm
diameter.times.3 mm thick according to JIS C 2134: 2007 and post
cured at 180.degree. C. for 4 hours. The specimen was held in a
25.degree. C./50% RH atmosphere for 48 hours.
[0130] Two platinum electrodes were placed in contact with the
surface of the specimen. While a voltage was applied between the
electrodes, a 0.1 wt % ammonium chloride aqueous solution was
dropped on the specimen at intervals of one droplet every 30
seconds. The test used five specimens (N=5). The value of maximum
voltage against which the specimen resisted without tracking
breakdown or sustaining flame during the measurement period of 50
droplets was determined as comparative tracking index (CTI). With
the fixed voltage of 600 V applied, the resin composition was
evaluated for tracking resistance by counting the number of
droplets of 0.1 wt % ammonium chloride aqueous solution.
TABLE-US-00001 TABLE 1 Example Comparative Example Formulation
(parts by weight) 1 2 3 1 2 3 (A) Silicone- E-01 46.6 60.6 modified
E-02 57.3 epoxy resin E-03 50.2 Epoxy resin polyfunctional epoxy
resin 60.0 46.0 (B) Silicone-modified P-01 53.4 49.8 54.0 phenolic
resin P-02 42.7 Phenolic resin phenol novolak resin 40.0 39.4 (C)
Black pigment carbon black 1.5 1.5 1.5 1.5 1.5 1.5 (D) Inorganic
filler fused silica powder 430 430 430 430 430 430 (E) Other
additives triphenylphosphine 1.0 1.0 2-ethyl-4-methylimidazole 1.0
1.0 1.0 1.0 carnauba wax 1.5 1.5 1.5 1.5 1.5 1.5 silane coupling
agent 1.2 1.2 1.2 1.2 1.2 1.2 Test Tracking CTI, droplet count
@600V >50 >50 >50 12 8 17 resistance (droplets)
[0131] The data in Table 1 demonstrate that the resin compositions
of Examples 1 to 3 have improved tracking resistance.
Resin Composition of Second Embodiment
Examples 4 to 7
[0132] Thermosetting resin compositions were prepared by combining
components (P), (A) and (F) and other components shown below in
accordance with the formulation described in Table 2, and melt
mixing them at 100.degree. C. for 3 minutes until uniform.
(P) Cyanate Ester Compound
[0133] A cyanate ester compound (Primaset.RTM. PT-60 by Lonza Ltd.,
cyanato equivalent 119) having the following formula (9)
##STR00026##
It is a mixture of compounds having formula (9) wherein n is from 0
to 10.
(A) Silicone-Modified Epoxy Resins E-01, E-02, E-04
[0134] Silicone-modified epoxy resins E-01 and E-02 are identical
with silicone-modified epoxy resins E-01 and E-02 used in the resin
compositions of the first embodiment. Silicone-modified epoxy resin
E-04 was synthesized in Synthesis Example 6.
Synthesis Example 6
[0135] A 1-L separable flask was charged with 0.16 g of a 0.5 wt %
chloroplatinic acid toluene solution, 80 g of toluene, and 272 g of
1,2-epoxy-4-vinylcyclohexane (Daicel Corp.), followed by stirring
and heating at an internal temperature of 60.degree. C. Thereafter,
141 g of 1,1,3,3-tetramethyldisiloxane (Shin-Etsu Chemical Co.,
Ltd.) was added dropwise over 30 minutes, and reaction run at
60.degree. C. for 1 hour. The resulting toluene solution was
distilled under reduced pressure, obtaining a silicone-modified
epoxy resin E-04 having a structure of the formula (10) shown
below. The resin E-04 had an epoxy equivalent of 257 g/eq.
##STR00027##
(F) Silicone-Modified Phenolic Resins P-01, P-02
[0136] These are identical with silicone-modified phenolic resins
P-01 and P-02 used in the resin compositions of the first
embodiment.
(F) Phenolic Resin
[0137] A phenol compound (MEH-7851SS by Meiwa Plastic Industries,
Ltd., phenolic hydroxyl equivalent 203) having the following
formula (11)
##STR00028##
It is a mixture of compounds having formula (11) wherein n is from
0 to 10.
Comparative Examples 4 and 5
[0138] Thermosetting resin compositions were prepared by combining
the components used in Examples 4 to 7 and additional component
shown below in accordance with the formulation described in Table
2, and melt mixing them at 100.degree. C. for 3 minutes until
uniform.
(A) Epoxy Resin
[0139] An epoxy resin compound (NC-3000 by Nippon Kayaku Co., Ltd.,
epoxy equivalent 272) having the following formula (12)
##STR00029##
It is a mixture of compounds having formula (12) wherein n is from
0 to 10.
[Tests]
Preparation of Cured Sample
[0140] Specimens of Examples 4 to 7 and Comparative Examples 4, 5
were prepared as follows. The thermosetting epoxy resin composition
was heat cured at 150.degree. C. for 1 hour and then at 180.degree.
C. for 4 hours into a specimen, which was subject to the following
tests.
Measurement of Tg
[0141] Each of the cured products of Examples 4 to 7 and
Comparative Examples 4, 5 was worked into a specimen of
5.times.5.times.15 mm. The specimen was set on a thermomechanical
analyzer TMA8310 (Rigaku Corp.). A change of a dimension of the
specimen was measured during the heating program from 25.degree. C.
to 300.degree. C. at a heating rate of 5.degree. C./min. A
dimensional change was plotted relative to temperature in the graph
of FIG. 1. From the graph showing dimensional change to temperature
relationship, the glass transition temperature (Tg) of the resin
compositions of Examples 4 to 7 and Comparative Examples 4, 5 was
determined by the Tg determining method described below.
[0142] Tg Determining Method
[0143] In the graph of FIG. 1, T1 and T2 are two arbitrary
temperatures at which tangents to the dimensional
change/temperature curve are available, below the temperature of
inflection point, and T1' and T2' are two arbitrary temperatures at
which tangents to the dimensional change/temperature curve are
available, above the temperature of inflection point. D1 and D2 are
dimensional changes at T1 and T2. D1' and D2' are dimensional
changes at T1' and T2'. Tg is given by the point of intersection
between a straight line connecting point (T1, D1) and point (T2,
D2) and a straight line connecting point (T1', D1') and point (T2',
D2').
Flexural Strength and Flexural Modulus
[0144] A specimen of 100.times.10.times.4 mm was prepared according
to JIS K 6911: 2006. The specimen was measured for flexural
strength and flexural modulus at room temperature (25.degree. C.)
by using an autograph tester (Shimadzu Corp.) and bending the
specimen at three points.
TABLE-US-00002 TABLE 2 Example Comparative Example Formulation
(parts by weight) 4 5 6 7 4 5 (P) Cyanate ester compound PT-60 60.0
60.0 60.0 60.0 60.0 60.0 (A) Silicone-modified E-01 24.1 12.5 epoxy
resin E-02 23.3 E-04 23.5 23.3 Epoxy resin NC-3000 22.9 7.1 (F)
Silicone-modified P-01 15.9 phenolic resin P-02 16.5 Phenolic resin
MEH-7851SS 16.7 16.7 17.1 20.4 Molar ratio of phenolic hydroxyl
group/cyanate group 0.163 0.163 0.163 0.163 0.167 0.199 Molar ratio
of epoxy group/cyanate group 0.283 0.233 0.171 0.231 0.167 0.198
Tests Tg (.degree. C.) 200 201 243 199 194 194 Flexural strength
(MPa) 31 32 35 46 36 36 Flexural modulus (MPa) 2280 1530 2020 2110
2700 2520
[0145] The data in Table 2 demonstrate that the resin compositions
of Examples 4 to 7 have a reduced modulus and mitigate the risk of
cracking or separation while maintaining thermal stability.
[0146] Japanese Patent Application Nos. 2017-099972 and 2017-100000
are incorporated herein by reference.
[0147] Although some preferred embodiments have been described,
many modifications and variations may be made thereto in light of
the above teachings. It is therefore to be understood that the
invention may be practiced otherwise than as specifically described
without departing from the scope of the appended claims.
* * * * *