U.S. patent number 10,385,203 [Application Number 15/691,189] was granted by the patent office on 2019-08-20 for heat-curable resin composition for semiconductor encapsulation.
This patent grant is currently assigned to SHIN-ETSU CHEMICAL CO., LTD.. The grantee listed for this patent is Shin-Etsu Chemical Co., Ltd.. Invention is credited to Naoyuki Kushihara, Tomoaki Nakamura, Kazuaki Sumita.
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United States Patent |
10,385,203 |
Sumita , et al. |
August 20, 2019 |
Heat-curable resin composition for semiconductor encapsulation
Abstract
Provided is a highly versatile heat-curable resin composition
for semiconductor encapsulation that exhibits a favorable water
resistance and abradability when used to encapsulate a
semiconductor device; and a superior fluidity and a small degree of
warpage even when used to perform encapsulation on a large-sized
wafer. The heat-curable resin composition for semiconductor
encapsulation comprises: (A) a cyanate ester compound having not
less than two cyanato groups in one molecule, and containing a
particular cyanate ester compound that has a viscosity of not
higher than 50 Pas; (B) a phenol curing agent containing a
resorcinol-type phenolic resin; (C) a curing accelerator; (D) an
inorganic filler surface-treated with a silane coupling agent; and
(E) an ester compound.
Inventors: |
Sumita; Kazuaki (Annaka,
JP), Nakamura; Tomoaki (Annaka, JP),
Kushihara; Naoyuki (Annaka, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Shin-Etsu Chemical Co., Ltd. |
Tokyo |
N/A |
JP |
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Assignee: |
SHIN-ETSU CHEMICAL CO., LTD.
(Tokyo, JP)
|
Family
ID: |
59829132 |
Appl.
No.: |
15/691,189 |
Filed: |
August 30, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180057663 A1 |
Mar 1, 2018 |
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Foreign Application Priority Data
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Sep 1, 2016 [JP] |
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2016-170688 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K
9/06 (20130101); C08K 5/175 (20130101); H01L
23/293 (20130101); H01L 23/295 (20130101); C08G
73/0655 (20130101); H01L 21/565 (20130101); H01L
23/296 (20130101); C08L 61/06 (20130101); C08K
3/36 (20130101); C08K 9/06 (20130101); C08L
79/04 (20130101); C08L 61/06 (20130101); C08K
5/103 (20130101); C08L 61/06 (20130101); C08L
61/12 (20130101); C08K 9/06 (20130101); C08K
5/175 (20130101); C08K 9/06 (20130101); C08L
79/04 (20130101); C08L 61/06 (20130101); C08K
5/103 (20130101); H01L 2924/3511 (20130101); C08G
14/12 (20130101); H01L 2224/32245 (20130101); H01L
2224/32225 (20130101); C08K 2201/003 (20130101) |
Current International
Class: |
C08L
61/06 (20060101); C08K 5/17 (20060101); C08K
3/36 (20060101); C08K 9/06 (20060101); H01L
21/56 (20060101); C08G 73/06 (20060101); H01L
23/29 (20060101); C08G 14/12 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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11-289034 |
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Oct 1999 |
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JP |
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2012-209453 |
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Oct 2012 |
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JP |
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2014-229771 |
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Dec 2014 |
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JP |
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2015-44939 |
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Mar 2015 |
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JP |
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2015-48472 |
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Mar 2015 |
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JP |
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Other References
Extended European Search Report dated Jan. 26, 2018, in European
Patent Application No. 17187236.9. cited by applicant .
Non-Final Office Action dated Feb. 21, 2019, in U.S. Appl. No.
15/905,039. cited by applicant.
|
Primary Examiner: Zimmer; Marc S
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch, LLP
Claims
What is claimed is:
1. A heat-curable resin composition for semiconductor
encapsulation, comprising: (A) a cyanate ester compound having not
less than two cyanato groups in one molecule, the cyanate ester
compound containing a cyanate ester compound (A-1) represented by
the following formula (1) and exhibiting a viscosity of not higher
than 50 Pas at 23.degree. C. when measured by a B-type rotary
viscometer in accordance with a method described in JIS
K7117-1:1999 ##STR00012## wherein n represents an integer of 0 or
1; each of R.sup.1 and R.sup.2 represents a hydrogen atom or an
alkyl group having 1 to 4 carbon atoms; and R.sup.3 represents a
divalent linking group selected from the groups expressed by the
following formulae (2) to (5) ##STR00013## (B) a phenol curing
agent containing a resorcinol-type phenolic resin represented by
the following formula (6) ##STR00014## wherein n represents an
integer of 0 to 10; each of R.sup.1 and R.sup.2 independently
represents a hydrogen atom or a monovalent group selected from the
group consisting of an alkyl group having 1 to 10 carbon atoms, an
allyl group and a vinyl group; and x represents 1 or 2; (C) a
curing accelerator in an amount of 0.01 to 5 parts by mass per 100
parts by mass of the component (A); (D) an inorganic filler that is
spherical, has an average particle diameter of 1 to 20 .mu.m when
measured by a laser diffraction method, is in an amount of 1,200 to
2,200 parts by mass per 100 parts by mass of a sum total of the
components (A) and (B), and has been surface-treated with a silane
coupling agent represented by the following formula (7)
R.sup.1.sub.a(OR.sup.2).sub.(3-a)Si--C.sub.3H.sub.6--R.sup.3 (7)
wherein a represents an integer of 0 to 3; R.sup.1 represents a
methyl group or an ethyl group; R.sup.2 represents an alkyl group
having 1 to 3 carbon atoms; and R.sup.3 represents a group selected
from the group consisting of the nitrogen-containing functional
groups represented by the following formulae (8) to (11)
##STR00015## and (E) an ester compound that is in an amount of 1 to
10 parts by mass per 100 parts by mass of the sum total of the
components (A) and (B), and is represented by the following formula
(12) R.sup.4--CH.sub.2CH.sub.2--NH--CH.sub.2CH.sub.2--R.sup.5 (12)
wherein each of R.sup.4 and R.sup.5 represents a saturated ester
residue having 2 to 30 carbon atoms.
2. The heat-curable resin composition for semiconductor
encapsulation according to claim 1, wherein cyanate ester compound
content in the component (A) except for the cyanate ester compound
(A-1) represented by the formula (1) is an amount of smaller than
10% by mass with respect to the whole amount of the component
(A).
3. The heat-curable resin composition for semiconductor
encapsulation according to claim 1, wherein the resorcinol-type
phenolic resin represented by the formula (6) is contained in the
component (B) by an amount of 10 to 100% by mass with respect to
the whole amount of the component (B).
4. The heat-curable resin composition for semiconductor
encapsulation according to claim 1, wherein cyanato groups in the
cyanate ester compound as the component (A) are in an amount of 0.5
to 100 equivalents per 1 equivalent of hydroxyl groups in the
phenol curing agent as the component (B).
5. The heat-curable resin composition for semiconductor
encapsulation according to claim 1, exhibiting a linear expansion
coefficient of 3.0 to 5.0 ppm/.degree. C. as a result of measuring
a 5.times.5.times.15 mm specimen at a rate of temperature increase
of 5.degree. C./min and under a load of 19.6 mN, in accordance with
a method described in JIS K 7197:2012.
6. A method for producing a resin-encapsulated semiconductor
device, comprising: a step of using a cured product of the
heat-curable resin composition for semiconductor encapsulation as
set forth in claim 1 to collectively encapsulate an entire silicon
wafer or substrate with at least one semiconductor element mounted
thereon, wherein the heat-curable resin composition for
semiconductor encapsulation is applied either in a pressurized
manner, or in a depressurized manner under a vacuum atmosphere,
before being heated and cured to encapsulate the semiconductor
element.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a heat-curable resin composition
for semiconductor encapsulation; and a method for producing a
resin-encapsulated semiconductor device, using a cured product of
the aforementioned composition.
Background Art
In recent years, mobile information-communication terminals such as
smart phones and tablets are equipped with thin, small-sized
multifunctional semiconductor devices that are capable of
performing high-speed processing, such that a large volume of
information can be processed at a high speed. These semiconductor
devices are produced as follows (JP-A-2014-229771). That is, TSV
(Through Silicon Via) technology is employed to connect
semiconductor elements through multi-layer bonding, followed by
performing flip chip bonding on the multilayered semiconductor
elements on an 8-inch or 12-inch silicon interposer, and then using
a heat-curable resin to encapsulate each interposer with a
plurality of the multilayered semiconductor elements mounted
thereon. The encapsulated package is then divided into individual
pieces after abrading the unwanted cured resin on the semiconductor
elements.
As for the production of a semiconductor device, encapsulation
molding can be performed without any major problems even under the
current situation, as long as a substrate such as a small-diameter
wafer is used. However, an epoxy resin or the like tends to exhibit
a significant contraction stress after encapsulation, when
performing molding on a wafer of a size of not smaller than 8
inches, or of a size of 20 inches in recent years; or on a panel of
a size of greater than 20 inches. For this reason, there has been a
problem that a semiconductor element(s) will be stripped off from a
substrate made of a metal or the like, which makes it difficult to
conduct mass production. In order to solve the aforementioned
problem associated with the increase in diameter of a wafer, a
glass substrate and a metal substrate, it has been required that a
resin be filled with a filler by an amount of not smaller than 90%
by mass, or that a contraction stress at the time of curing be
reduced through a reduction in elasticity of a resin
(JP-A-2012-209453).
However, in the case where a silicon interposer is to be entirely
encapsulated by a heat-curable resin, a significant warpage will
occur due to a difference in thermal expansion coefficient between
silicon and the heat-curable resin. A significant warpage makes it
unsuitable to perform an abrading step and a dicing step later.
That is, it has been a major technical issue to prevent
warpage.
Conventionally, there has been used an encapsulation material
prepared by filling a composition containing an epoxy resin and a
curing agent such as an acid anhydride and a phenolic resin with a
filler by an amount of not smaller than 85% by mass, and then
adding a rubber and/or a thermoplastic resin thereto for stress
relaxation. This type of composition bears a problem that a warpage
will occur due to a thermal history associated with a step(s) in 3D
packaging, and that such warpage will then lead to damages of a
semiconductor element(s) or even the breakage of a wafer itself.
Meanwhile, since the resin component in a low-elastic resin
material as typified by a conventional silicone compound is soft,
there have been problems that resin clogging will occur at the time
of performing abrading, and that resin cracks will occur during a
reliability test (JP-A-Hei11-289034).
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a highly
versatile heat-curable resin composition for semiconductor
encapsulation that exhibits a favorable water resistance and
abradability when used to encapsulate a semiconductor device; and a
superior fluidity and a small degree of warpage even when used to
perform encapsulation on a large-sized wafer.
The inventors of the present invention diligently conducted a
series of studies to solve the abovementioned problems, and
completed the invention as follows. That is, the inventors found
that the above objective could be achieved by a heat-curable resin
composition obtained by combining a particular cyanate ester
compound, a particular phenol curing agent, a particular inorganic
filler and a particular ester compound.
Specifically, the present invention is to provide the following
heat-curable resin composition for semiconductor encapsulation; and
a method for producing a resin-encapsulated semiconductor device,
using a cured product of such composition.
[1]
A heat-curable resin composition for semiconductor encapsulation,
comprising:
(A) a cyanate ester compound having not less than two cyanato
groups in one molecule, the cyanate ester compound containing a
cyanate ester compound (A-1) represented by the following formula
(1) and exhibiting a viscosity of not higher than 50 Pas at
23.degree. C. when measured by a B-type rotary viscometer in
accordance with a method described in JIS K7117-1:1999
##STR00001##
wherein n represents an integer of 0 or 1; each of R.sup.1 and
R.sup.2 represents a hydrogen atom or an alkyl group having 1 to 4
carbon atoms; and R.sup.3 represents a divalent linking group
selected from the groups expressed by the following formulae (2) to
(5)
##STR00002##
(B) a phenol curing agent containing a resorcinol-type phenolic
resin represented by the following formula (6)
##STR00003##
wherein n represents an integer of 0 to 10; each of R.sup.1 and
R.sup.2 independently represents a hydrogen atom or a monovalent
group selected from the group consisting of an alkyl group having 1
to 10 carbon atoms, an allyl group and a vinyl group; and x
represents 1 or 2;
(C) a curing accelerator in an amount of 0.01 to 5 parts by mass
per 100 parts by mass of the component (A);
(D) an inorganic filler that is spherical, has an average particle
diameter of 1 to 20 .mu.m when measured by a laser diffraction
method, is in an amount of 1,200 to 2,200 parts by mass per 100
parts by mass of a sum total of the components (A) and (B), and has
been surface-treated with a silane coupling agent represented by
the following formula (7)
R.sup.1.sub.a(OR.sup.2).sub.(3-a)Si--C.sub.3H.sub.6--R.sup.3
(7)
wherein a represents an integer of 0 to 3; R.sup.1 represents a
methyl group or an ethyl group; R.sup.2 represents an alkyl group
having 1 to 3 carbon atoms; and R.sup.3 represents a group selected
from the group consisting of the nitrogen-containing functional
groups represented by the following formulae (8) to (11)
##STR00004## and
(E) an ester compound that is in an amount of 1 to 10 parts by mass
per 100 parts by mass of the sum total of the components (A) and
(B), and is represented by the following formula (12)
R.sup.4--CH.sub.2CH.sub.2--NH--CH.sub.2CH.sub.2--R.sup.5 (12)
wherein each of R.sup.4 and R.sup.5 represents a saturated ester
residue having 2 to 30 carbon atoms. [2]
The heat-curable resin composition for semiconductor encapsulation
according to [1], wherein cyanate ester compound content in the
component (A) except for the cyanate ester compound (A-1)
represented by the formula (1) is an amount of smaller than 10% by
mass with respect to the whole amount of the component (A).
[3]
The heat-curable resin composition for semiconductor encapsulation
according to [1] or [2], wherein the resorcinol-type phenolic resin
represented by the formula (6) is contained in the component (B) by
an amount of 10 to 100% by mass with respect to the whole amount of
the component (B).
[4]
The heat-curable resin composition for semiconductor encapsulation
according to any one of [1] to [3], wherein cyanato groups in the
cyanate ester compound as the component (A) are in an amount of 0.5
to 100 equivalents per 1 equivalent of hydroxyl groups in the
phenol curing agent as the component (B).
[5]
The heat-curable resin composition for semiconductor encapsulation
according to any one of [1] to [4], exhibiting a linear expansion
coefficient of 3.0 to 5.0 ppm/.degree. C. as a result of measuring
a 5.times.5.times.15 mm specimen at a rate of temperature increase
of 5.degree. C./min and under a load of 19.6 mN, in accordance with
a method described in JIS K 7197:2012.
[6]
A method for producing a resin-encapsulated semiconductor device,
comprising:
a step of using a cured product of the heat-curable resin
composition for semiconductor encapsulation as set forth in any one
of [1] to [5] to collectively encapsulate an entire silicon wafer
or substrate with at least one semiconductor element mounted
thereon, wherein the heat-curable resin composition for
semiconductor encapsulation is applied either in a pressurized
manner, or in a depressurized manner under a vacuum atmosphere,
before being heated and cured to encapsulate the semiconductor
element.
According to the present invention, there can be obtained a
semiconductor device superior in heat resistance and moisture
resistance, and barely exhibiting warpage when cooled after being
heated and cured, even in the cases of encapsulating a
semiconductor element array with at least one semiconductor element
mounted on an inorganic substrate, a metal substrate or an organic
substrate through an adhesive agent (die bonding material); or
encapsulating a large wafer with a semiconductor(s) formed
thereon.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram showing a method for determining a
glass-transition temperature.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail hereunder. However,
the invention is not limited to the following examples.
(A) Cyanate Ester Compound
A component (A) is a main component of the composition of the
invention, and is a cyanate ester compound having at least two
cyanato groups. The component (A) contains the compound represented
by the above formula (1).
It is preferred that the compound i.e. (A-1) represented by the
above formula (1) exhibit a viscosity of not higher than 50 Pas at
23.degree. C., particularly preferably not higher than 20 Pas at
23.degree. C., when measured by a B-type viscometer in accordance
with a method described in JIS K7117-1:1999. When this viscosity is
greater than 50 Pas, the composition cannot be filled with a
sufficient amount of an inorganic filler such that the expansion
coefficient of the composition will become large. In such case, a
significant warpage may be observed as a result of performing
molding on a wafer of a size of not smaller than 12 inches, thus
making it impossible to obtain a sheet-shaped product.
In the present invention, the cyanate ester compound i.e. (A-1)
represented by the formula (1) may be mixed and used in combination
with another cyanate ester compound having at least two cyanato
groups in one molecule. As such cyanate ester compound other than
that represented by the formula (1) that has at least two cyanato
groups, there may be used a known cyanato ester compound. Examples
of such cyanato ester compound include bis (4-cyanatophenyl)
methane; bis (3-methyl-4-cyanatophenyl) methane; bis
(3,5-dimethyl-4-cyanatophenyl) methane; 1,1-bis (4-cyanatophenyl)
ethane; 2,2-bis (4-cyanatophenyl) propane; 2,2-bis
(4-cyanatophenyl)-1,1,1,3,3,3-hexafluoropropane;
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) diphenylcyanate; bis
(4-cyanatophenyl) thioether; bis (4-cyanatophenyl) sulfone; tris
(4-cyanato-phenyl) phosphine; a phenol novolac-type cyanate; a
cresol novolac-type cyanate; and a dicyclopentadiene novolac-type
cyanate.
It is preferred that the cyanate ester compound i.e. (A-1)
represented by the formula (1) be contained in the whole cyanate
ester compound as the component (A) having at least two cyanato
groups, by an amount of not smaller than 90% by mass. When the
cyanate ester compound represented by the formula (1) is contained
in an amount of smaller than 90% by mass, the composition cannot be
filled with a sufficient amount of an inorganic filler such that
there may not be obtained a sheet-shaped product. In other words,
it is preferred that the cyanate ester compound other than the
cyanate ester compound represented by the formula (1) be contained
in the whole component (A) by an amount of smaller than 10% by
mass.
It is preferred that the cyanate ester compound as the component
(A) be contained in the whole resin composition by an amount of 3
to 10% by mass, more preferably 3 to 7% by mass, most preferably 3
to 5% by mass.
(B) Phenol Curing Agent
A component (B) is a phenol curing agent containing a
resorcinol-type phenolic resin represented by the following formula
(6).
##STR00005##
In the formula (6), n represents an integer of 0 to 10; each of
R.sup.1 and R.sup.2 independently represents a hydrogen atom or a
monovalent group selected from the group consisting of an alkyl
group having 1 to 10 carbon atoms, an allyl group and a vinyl
group.
It is preferred that "n" in the above formula (6) be 0 to 10 in
terms of melt fluidity. When "n" is greater than 10, the component
(B) will not melt at a temperature of 100.degree. C. or lower, thus
resulting in an impaired fluidity of the resin composition. Each of
R.sup.1 and R.sup.2 represents a hydrogen atom or a monovalent
group selected from the group consisting of an alkyl group having 1
to 10 carbon atoms, an allyl group and a vinyl group; and it is
preferred that each of R.sup.1 and R.sup.2 be a hydrogen atom or a
monovalent group selected from the group consisting of an alkyl
group having 1 to 4 carbon atoms, an allyl group and a vinyl group.
R.sup.1s may be functional groups that are identical to or
different from one another. Further, R.sup.2s may also be
functional groups that are identical to or different from one
another. Here, when each of R.sup.1 and R.sup.2 is a group having
more than 10 carbon atoms, the resin composition will not exhibit a
sufficient heat resistance.
Further, as the component (B), two or more kinds of the
resorcinol-type phenolic resins (formula (6)) with different values
of "n" may be mixed together and used in combination; or there may
be used a resorcinol-type phenolic resin (formula (6)) exhibiting a
variation in the value of "n."
It is preferred that the phenol curing agent (B) and the cyanate
ester compound (A) be added at a ratio at which the cyanato groups
(CN groups) in the component (A) will be in an amount of 0.5 to 100
equivalents, more preferably 1 to 50 equivalents, or even more
preferably 5 to 35 equivalents, per 1 equivalent of the hydroxyl
groups (OH groups) in the phenol curing agent (B). When the cyanato
groups (CN groups) are in an amount of greater than 100 equivalents
per 1 equivalent of the hydroxyl groups (OH groups), the resin
composition will be cured insufficiently; and when the cyanato
groups (CN groups) are in an amount of smaller than 0.5 equivalents
per 1 equivalent of the hydroxyl groups (OH groups), the heat
resistance of the cyanate ester compound (A) itself may be
impaired.
Further, with regard to the phenol curing agent (B), it is
preferred that the resorcinol-type phenolic resin represented by
the formula (6) be contained in the whole component (B) by an
amount of 10 to 100% by mass. When the component (B) contains the
resorcinol-type phenolic resin represented by the formula (6), a
resin viscosity at the time of melting the component (B) can be
reduced, and a curing reaction of the cyanate ester compound (A)
can be promoted. Moreover, since the resorcinol-type phenolic resin
itself has a high heat resistance, there can be obtained a cured
product having a superior heat resistance. Here, as a phenol curing
agent other than the resorcinol-type phenolic resin represented by
the formula (6), there may be listed a phenol curing agent
represented by the following formula (13).
##STR00006##
In the formula (13), R.sup.2 represents a monovalent hydrocarbon
group having a double bond(s) and not more than 10 carbon atoms;
R.sup.3 represents any one of the divalent hydrocarbon groups
represented by the following formulae.
##STR00007##
In the formula (14), R.sup.4 represents a hydrogen atom or a
monovalent hydrocarbon group having not more than 10 carbon
atoms.
(C) Curing Accelerator
Examples of a component (C) include 1,8-diazabicyclo [5.4.0]
undecene-7 (DBU); 1,5-diazabicyclo [4.3.0] nonene-5 (DBN); N-alkyl
substituents of these DBU and DBN; N-aryl substituents of these DBU
and DBN; salts of these nitrogen-containing heterocyclic compounds;
and amine-based curing accelerators. It is preferred that the
curing accelerator as the component (C) be added in an amount of
not larger than 5 parts by mass, more preferably 0.01 to 5 parts by
mass, per 100 parts by mass of the component (A).
Specific examples of salts of DBU include a phenolate, an octylate,
a p-toluenesulfonate, a formate, an orthophthalate, a trimellitic
anhydride salt, a phenol novolac resin salt and a
tetraphenylborate.
Specific examples of salts of DBN include a phenolate, an octylate,
a p-toluenesulfonate, a formate, an orthophthalate, a trimellitic
anhydride salt, a phenol novolac resin salt and a
tetraphenylborate.
Examples of the amine-based curing accelerator include aromatic
amine-based curing accelerators such as
3,3'-diethyl-4,4'-diaminodiphenylmethane,
3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane,
3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane,
2,4-diaminotoluene, 1,4-phenylenediamine, 1,3-phenylenediamine,
diethyltoluenediamine, 3,4'-diaminodiphenyl ether,
3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane,
4,4'-diaminodiphenylmethane, 3,3'-diaminobenzidine, orthotolidine,
3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,6-diaminotoluene and
1,8-diaminonaphthalene; chain aliphatic polyamines such as N,N'-bis
(3-aminopropyl) ethylenediamine, 3,3'-diaminodipropylamine,
1,8-diaminooctane, 1,10-diaminodecane, diethylenetriamine,
triethylenetetramine and tetraethylenepentamine; cyclic aliphatic
polyamines such as 1,4-bis (3-aminopropyl) piperazine,
N-(2-aminoethyl) piperazine, N-(2-aminoethyl) morpholine and
isophoronediamine; polyamidoamine; an imidazole-based curing
accelerator; and a guanidine-based curing accelerator. The
abovementioned polyamidoamine is produced by condensation of a
dimer acid and a polyamine, and examples of such polyamidoamine
include adipic dihydrazide and
7,11-octadecadiene-1,18-dicarbohydrazide. Examples of the
abovementioned imidazole-based curing accelerator include
2-methylimidazole, 2-ethyl-4-methylimidazole and 1,3-bis
(hydrazinocarbonoethyl)-5-isopropylhydantoin. Examples of the
abovementioned guanidine-based curing accelerator include aliphatic
amines such as 1,3-diphenylguanidine and 1,3-o-triguanidine. It is
particularly preferred that an imidazole-based curing accelerator
be used.
(D) Inorganic Filler
As an inorganic filler added to the resin composition of the
present invention, there may be used those normally added to an
epoxy resin composition. Specific examples of such inorganic filler
include silicas such as a molten silica and a crystalline silica;
alumina; silicon nitride; aluminum nitride; boron nitride; titanium
oxide; and glass fibers.
It is preferred that such inorganic filler be spherical; and have
an average particle diameter of 1 to 20 particularly 3 to 15 .mu.m
when measured by a laser diffraction method. Moreover, such
inorganic filler is surface-treated with a silane coupling agent
represented by the following formula (7).
In this specification, the notion "spherical" does not only refer
to a case where the shapes of the particles are true spheres, but
also to a case where the shapes of the particles are deformed
spheres exhibiting on average an aspect ratio (longest-axis
length/shortest-axis length) of 1 to 4 in general, preferably 1 to
2, more preferably 1 to 1.6, or even more preferably 1 to 1.4. The
shapes of the particles can be confirmed by observing these
particles through an optical microscope and/or an electronic
microscope.
R.sup.1.sub.a(OR.sup.2).sub.(3-a)Si--C.sub.3H.sub.6--R.sup.3
(7)
In the formula (7), R.sup.1 represents a methyl group or an ethyl
group; R.sup.2 represents an alkyl group having 1 to 3 carbon
atoms; R.sup.3 represents a group selected from the group
consisting of the nitrogen-containing functional groups represented
by the following formulae (8) to (11); and a represents an integer
of 0 to 3.
##STR00008##
The aforementioned surface treatment improves the affinity between
the inorganic filler (D) and the cyanate ester compound (A) so as
to strengthen the bond between the component (A) and the component
(D), and then allow the fluidity of the resin composition to be
improved significantly. A known method may be employed as such
surface treatment method using the silane coupling agent. In fact,
there are no particular restrictions on this surface treatment
method.
One example of the silane coupling agent used as a surface
treatment agent for the component (D) may be
N-phenyl-3-aminopropyltrimethoxysilane.
It is preferred that the silane coupling agent represented by the
formula (7) be added in an amount of 0.2 to 0.5 parts by mass per
100 parts by mass of the inorganic filler. When the silane coupling
agent is added in a small amount, the cyanate ester compound and
the inorganic filler may not be bonded together in a sufficient
manner, or there may not be achieved a sufficient fluidity of the
resin composition. Meanwhile, a larger expansion coefficient may be
resulted if the silane coupling agent is added in a large
amount.
It is preferred that the component (D) be added in an amount of
1,200 to 2,200 parts by mass, more preferably 1,400 to 2,000 parts
by mass, per 100 parts by mass of a sum total of the components (A)
and (B). When the component (D) is added in an amount smaller than
such lower limit value, a molded wafer will exhibit a significant
warpage in a way such that there cannot be achieved a sufficient
strength. Further, when the component (D) is added in an amount
greater than such upper limit, the resin composition will exhibit a
significantly poor fluidity, and a semiconductor element(s)
arranged on a submount cannot be encapsulated completely.
(E) Ester Compound
A component (E) is an ester compound represented by the following
formula (12).
R.sup.4--CH.sub.2CH.sub.2--NH--CH.sub.2CH.sub.2--R.sup.5 (12) Each
of R.sup.4 and R.sup.5 represents a saturated ester residue having
2 to 30 carbon atoms.
In the formula (12), it is preferred that each of R.sup.4 and
R.sup.5 be a saturated ester residue having 15 to 30 carbon atoms,
preferably 20 to 30 carbon atoms. Specifically, it is preferred
that each of R.sup.4 and R.sup.5 be a montanic acid ester.
It is preferred that the component (E) be added in an amount of 1
to 10 parts by mass, more preferably 1 to 6 parts by mass, per 100
parts by mass of the sum total of the components (A) and (B). When
the component (E) is added in an amount of smaller than 1 part by
mass, the wafer may exhibit a significant warpage. When the amount
of the component (E) added is greater than 10 parts by mass, a
significantly poor formability will be observed, and the adhesion
to a silicon wafer and a silicon chip may be impaired in a
significant manner as well. As a typical compound as the component
(E), NC133 (by Itoh Oil Chemicals Co., Ltd.) is preferred.
(F) Other Additives
The heat-resistant resin composition of the invention can be
obtained by combining the above components (A) to (E) in given
amounts. However, other additives may also be added to the
composition of the invention if necessary, without impairing the
objectives and effects of the present invention. Examples of such
additives include an inorganic filler, a flame retardant, an ion
trapping agent, an antioxidant, an adhesion imparting agent, a low
stress agent and a coloring agent.
The flame retardant is added to impart a flame retardant property.
Here, all the known flame retardants may be used in the present
invention. Examples of such flame retardant include a phosphazene
compound, a silicone compound, a zinc molybdate-supported talc, a
zinc molybdate-supported zinc oxide, aluminum hydroxide, magnesium
hydroxide and molybdenum oxide.
The ion trapping agent is added to trap the ion impurities
contained in the resin composition, and avoid a thermal degradation
and a moisture absorption degradation. Here, all the known ion
trapping agents may be used in the present invention. Examples of
such ion trapping agents include hydrotalcites, a bismuth hydroxide
compound and rare-earth oxides.
The adhesion imparting agent is added to impart an adhesion with
respect to a chip and a substrate that are to be encapsulated.
Here, all the known adhesion imparting agents may be used in the
present invention. Examples of such adhesion imparting agents
include a silane compound and a polysiloxane compound that have in
their molecules a hydrolyzable silyl group(s); and an adhesive
functional group(s) such as a vinyl group, an amino group, an epoxy
group, a (metha) acrylic group and a mercapto group.
Examples of such silane compound include vinyltrimethoxysilane,
vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)
ethyltrimethoxysilane, .gamma.-glycidoxypropyltrimethoxysilane,
.gamma.-glycidoxypropyltriethoxysilane,
.gamma.-glycidoxypropylmethyldiethoxysilane,
.gamma.-methacryloxypropylmethyldiethoxysilane,
.gamma.-acryloxypropyltrimethoxysilane,
N-2-(aminoethyl)-3-aminopropyltrimethoxysilane,
N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane,
N-phenyl-3-aminopropyltrimethoxysilane,
.gamma.-aminopropyltrimethoxysilane and
.gamma.-mercaptopropyltrimethoxysilane. Further, the above
polysiloxane compound may be circular, chainlike or netlike.
Although the amount of the component (F) added varies depending on
the intended purpose of the resin composition, it is normally added
in an amount of not larger than 20% by mass with respect to the
whole composition.
Method for Preparing Heat-Curable Resin Composition
The heat-curable resin composition of the invention can, for
example, be prepared through the method shown below.
In the beginning, a mixture of the components (A) and (B) is
obtained by simultaneously or separately mixing, stirring, and/or
dispersing the cyanate ester compound (A) and the phenol curing
agent (B) while performing a heating treatment if necessary. A
mixture of the components (A) to (C) and (E) is then obtained by
mixing, stirring, and/or dispersing the curing accelerator (C), the
ester compound (E) and the mixture of the components (A) and (B).
Further, a mixture of the components (A) to (E) is obtained by
mixing, stirring, and/or dispersing the inorganic filler (D); and
the mixture of the components (A) to (C) and (E). In addition, at
least one of the flame retardant and ion trapping agent as an
additive(s) may be added to mixed with the mixture of the
components (A) and (B), the mixture of the components (A) to (C)
and (E), and the mixture of the components (A) to (E), depending on
the intended use.
There are no particular restrictions on a device(s) for performing,
for example, mixing, stirring and dispersion. However, specific
examples of such device(s) include a kneader equipped with a
stirring and heating devices, a twin-roll mill, a triple-roll mill,
a ball mill, a continuous extruder, a planetary mixer and a
mass-colloider. These devices may also be appropriately used in
combination.
The heat-curable resin composition of the present invention can be
molded through the conventional compression molding or laminating
molding. Particularly, it is preferred that compression molding be
performed. In such case, it is preferred that the resin composition
be molded at a molding temperature of 160 to 180.degree. C. for 300
to 600 sec, and that post-curing be then performed at 160 to
180.degree. C. for 1 to 6 hours.
The composition of the invention is capable of yielding a small
level of warpage even when molded on a large-sized wafer such as an
8 inch, 12 inch or 20 inch wafer. Further, the cured product of the
resin composition of the invention is superior in mechanical
strength and insulation properties, and a semiconductor device
encapsulated by such cured product is superior in long-term
reliability. Moreover, the resin composition of the invention is
also superior in productivity due to the fact that molding failures
such as flow mark and filling failure will not occur when using the
device(s) for conventional molding such as compression or
laminating molding under the conventional conditions.
In this specification, a large-sized wafer refers to a substrate
having a dimeter not smaller than 8 inches (i.e. 20 cm). Examples
of such substrate include 8 inch, 12 inch and 20 inch silicon
wafers.
A flow mark referred to in this specification is a white flow mark
radially formed from the center of the molded product toward the
outer side. The occurrence of such flow mark may lead to, for
example, a poor appearance; a variation in the properties of the
cured product due to an ununiformly dispersed silica; and an
impaired reliability associated with such variation.
A filling failure referred to in this specification refers to a
missing portion of resin that occurs on the outer circumferential
region of a wafer. The occurrence of such filling failure may cause
a sensor to erroneously recognize the unfilled portion as a notch
when transporting the wafer in a later step(s). There, a position
adjustment property may be impaired.
Working Example
Described below are working examples of the present invention.
However, the invention is not limited to the following examples.
Here, a viscosity referred to in this specification is a viscosity
measured by a B-type rotary viscometer at 23.degree. C., in
accordance with a method described in JIS K7117-1:1999.
Method for Producing Sheet-Like Heat-Curable Resin Composition
A heat-curable resin composition was obtained by mixing all the
following components as those contained in the heat-curable resin
composition at the ratios shown in Table 1, and then kneading the
same with a twin-roll mill. In Table 1, the unit for the numerical
values representing the compounding ratios is "part by mass."
The mixture of the heat-curable resin composition obtained above
was applied to the surface of a polyester film (protection layer)
that had been subjected to a mold release treatment, followed by
using a heated roll mill to form the mixture to a thickness of 100
.mu.m. In this way, obtained were sheet-like cured products of
working examples 1 to 5 and comparative examples 1 to 7. In
comparative examples 4 to 7, a poor wettability was observed
between the resin and the inorganic filler such that the
composition of the invention failed to be formed into a sheet-like
shape. The following tests and evaluations were then performed on
the compositions (working examples 1 to 5; comparative examples 1
to 3) that had been able to be formed into a sheet-like
shape(s).
(A) Cyanate Ester Compound
(A1) 1,1-bis (4-cyanatophenyl) ethane represented by the following
formula (17) (viscosity: 0.08 Pas) (product name: LECy by LONZA
Group Ltd.)
##STR00009##
(A2) Phenol novolac-type cyanate ester represented by the following
formula (18) (n=0 to 2) (viscosity: 250 Pas) (product name: PT30 by
LONZA Group Ltd.)
##STR00010## (B) Phenol Curing Agent
(B1) Resorcinol-type phenolic resin represented by the following
formula (19) (n=0 to 4; each of R.sup.1 and R.sup.2 represents an
allyl group; weight-average molecular weight 450 to 600; equivalent
107) (product name: MEH-8400 by MEIWA PLASTIC INDUSTRIES, LTD)
(B2) Resorcinol-type phenolic resin represented by the following
formula (19) (n=5 to 7; each of R.sup.1 and R.sup.2 represents an
allyl group; weight-average molecular weight 800 to 1,100;
equivalent 132) (by MEIWA PLASTIC INDUSTRIES, LTD)
##STR00011## (C) Curing Accelerator
(C1) DBU-type tetraphenylborate salt (product name: U-CAT 5002 by
by San-Apro Ltd.)
(D) Inorganic Filler
(D1) Treated Silica
A treated silica (D1) was prepared by performing dry surface
treatment on 100 parts by mass of a base spherical molten silica
(spherical molten silica with an average particle diameter of 12
.mu.m (by TATSUMORI LTD.)) with 0.3 parts by mass of an
N-phenyl-3-aminopropyltrimethoxysilane (product name: KBM573 by
Shin-Etsu Chemical Co., Ltd.).
(D2) Treated Silica
A treated silica (D2) was prepared by performing dry surface
treatment on 100 parts by mass of a base spherical molten silica
(spherical molten silica with an average particle diameter of 12
.mu.m (by TATSUMORI LTD.)) with 0.3 parts by mass of a
.gamma.-glycidoxypropyltrimethoxysilane (product name: KBM403 by
Shin-Etsu Chemical Co., Ltd.).
(D3) Treated Silica
A treated silica (D3) was prepared by performing dry surface
treatment on 100 parts by mass of a base spherical molten silica
(spherical silica with an average particle diameter of 0.8 .mu.m
(by TATSUMORI LTD.)) with 0.3 parts by mass of the
N-phenyl-3-aminopropyltrimethoxysilane (product name: KBM573 by
Shin-Etsu Chemical Co., Ltd.).
(D4) Non-Treated Silica
The spherical molten silica used in (D1) (by TATSUMORI LTD.,
average particle diameter of 12 .mu.m) was used without performing
surface treatment thereon.
(E) Ester Compound
(E1) Montanic acid ester compound represented by the following
formula (20)
C.sub.27H.sub.55--COO--CH.sub.2CH.sub.2--NH--CH.sub.2CH.sub.2--OOC---
C.sub.27H.sub.55 (20)
(F) Other Additives
(F1) Adhesion imparting agent:
.gamma.-glycidoxypropyltrimethoxysilane (product name: KBM403 by
Shin-Etsu Chemical Co., Ltd.).
(F2) Coloring agent: carbon black (product name: Mitsubishi carbon
black 3230MJ by Mitsubishi Chemical Corporation)
Test and Evaluation Method
Glass-Transition Temperature and Linear Expansion Coefficient
Each of the sheet-like cured products produced in the working and
comparative examples in accordance with JIS K 7197:2012, was
processed into a specimen of a size of 5.times.5.times.15 mm,
followed by placing the same in a thermal dilatometer TMA 8140C (by
Rigaku Corporation). A change in size of the specimen was then
measured at a rate of temperature increase of 5.degree. C./min from
25.degree. C. to 300.degree. C., with a constant load of 19.6 mN
being applied to the specimen. The correlation between such change
in size and the temperatures was then plotted on a graph. The
glass-transition temperatures in the working and comparative
examples were later obtained based on such graph showing the
correlation between the change in size and the temperatures, and
through the following method for determining the glass-transition
temperature(s).
Method for Determining Glass-Transition Temperature
In FIG. 1, T.sub.1 and T.sub.2 represent two arbitrary temperatures
that are not higher than the temperature at the inflection point
and by which a tangent line to the size change-temperature curve
can be drawn; whereas T.sub.1' and T.sub.2' represent two arbitrary
temperatures that are not lower than the temperature at the
inflection point and by which a similar tangent line can be drawn.
D.sub.1 and D.sub.2 individually represent a change in size at
T.sub.1 and a change in size at T.sub.2; whereas D.sub.1' and
D.sub.2' individually represent a change in size at T.sub.1' and a
change in size at T.sub.2'. The glass-transition temperature (Tg)
is then defined as the temperature at the point of intersection
between a straight line connecting points (T.sub.1, D.sub.1) and
(T.sub.2, D.sub.2) and a straight line connecting points (T.sub.1',
D.sub.1') and (T.sub.2', D.sub.2'). The slope between T.sub.1 and
T.sub.2 is defined as a linear expansion coefficient (linear
expansion coefficient 1) of a region where the temperature is not
larger than Tg, whereas the slope between T.sub.1' and T.sub.2' is
defined as a linear expansion coefficient (linear expansion
coefficient 2) of a region where the temperature is not smaller
than Tg.
Warpage Measurement
Using a 12-inch silicon wafer of a thickness of 775 .mu.m, the
heat-curable resin composition was subjected to compression molding
in a wafer mold by APIC YAMADA CORPORATION at 175.degree. C. for
600 sec to obtain a molded product of a resin thickness of 500
.mu.m, followed by completely curing (i.e. post-curing) the same
under the condition of 180.degree. C. for 1 hour. Warpage (mm) was
measured thereafter.
Reliability Test
Semiconductor chips were prepared as follows. That is, a screen
printer for thick film (THICK FILM PRINTER TYPE MC 212) was used to
print on an 8-inch silicon wafer of a thickness of 200 .mu.m a die
bonding material SFX-513M1 (by Shin-Etsu Chemical Co., Ltd.) at a
thickness of 20 .mu.m. A dicing apparatus was then used to cut the
printed specimen into 7-mm dices while the specimen was still in
B-stage.
Next, a flip chip bonder (NM-SB50A by Panasonic Corporation) was
used to bond the produced semiconductor chips to the 8-inch and 200
.mu.m-thick silicon wafer, under a condition of 10N/150.degree.
C./1.0 sec. In this way, there was obtained a silicon wafer with
the semiconductor chips mounted thereon.
The semiconductor chip-mounted silicon wafer was then placed in a
compression molding device, followed by placing thereon an
appropriate amount of the heat-curable resin composition so as to
then cure the heat-curable resin composition at 175.degree. C. for
10 min, where a maximum value of the molding pressure applied was
15 to 30 MPa. A silicon wafer was thus obtained. The amount of the
heat-curable resin composition was adjusted to that allowing the
resin thickness to become 500 .mu.m.+-.10 .mu.m after molding. Such
silicon wafer was then subjected to post-curing where the silicon
wafer was heat-treated in an oven at 180.degree. C. for an hour.
Later, a dicing apparatus was again used to cut the post-cured
silicon wafer into 7.1 mm.times.7.1 mm dices, thus obtaining a
separated resin-mounted semiconductor chip having a thickness of
500 .mu.m.+-.10 .mu.m.
The above semiconductor chips were then subjected to a hygroscopic
treatment for 168 hours under a condition of 85.degree. C. and 85%
RH. The semiconductor chips thus treated were further subjected to
a solder heat resistance test (peeling inspection) where the
semiconductor chips were inserted through a reflow oven three
times, the reflow oven being previously configured in a manner such
that a temperature range was within 255 to 260.degree. C. (i.e.
maximum temperature 260.degree. C.) for 30 sec.+-.3 sec. An
ultrasonic flaw detector (QUANTUM 350 by SONIX) was used to inspect
a peeling state inside the semiconductor chips in a nondestructive
manner with a 75 MHz probe. Here, examples exhibiting no peelings
or cracks were marked "Favorable," whereas examples exhibiting
peelings or cracks were marked "NG."
TABLE-US-00001 TABLE 1 Comparative Working example example
Composition (part by mass) 1 2 3 4 5 1 (A)Cyanate ester compound
(A1) (Viscosity: 0.08 Pa s) 95 95 95 95 90 95 (A2) (Viscosity: 250
Pa s) 5 (B)Phenol curing agent (B1) Resorcinol type 5 5 5 5 5 (B2)
Resorcinol type 5 (C)Curing accelerator (C1) DBU-type
tetraphenylborate salt 0.5 0.5 0.5 0.5 0.5 0.5 (D)Inorganic filler
(D1) Treated silica (KBM573, 12 .mu.m) 1850 1850 1850 1850 1400
1850 (D2) Treated silica (KBM403, 12 .mu.m) (D3) Treated silica
(KBM573, 0.8 .mu.m) (D4) Silica (12 .mu.m) (E)Ester compound (E1)
Montanic acid ester compound 3 3 5 1 3 0 (F)Other additives (F1)
Adhesion imparting agent 1 1 1 1 1 1 (F2) Carbon black 1 1 1 1 1 1
Evaluation item Sheet-like shape Favorable Favorable Favorable
Favorable Favorable Favorable Glass-transition temperature [Tg]
(.degree. C.) 220 225 225 220 240 250 Linear expansion coefficient
1 (ppm/.degree. C.) 4.1 4.1 4.2 4.5 4.1 4.0 Filling failure (Yes
No) No No No No No No Warpage amount (mm) <1 <1 <1 2 <1
4 Reliability test Presence or absence of peeling, Favorable
Favorable Favorable Favorable Favorable Favorable crack (IR reflow)
Comparative example Composition (part by mass) 2 3 4 5 6 7
(A)Cyanate ester compound (A1) (Viscosity: 0.08 Pa s) 95 95 95 95
95 95 (A2) (Viscosity: 250 Pa s) (B)Phenol curing agent (B1)
Resorcinol type 5 5 5 5 5 5 (B2) Resorcinol type (C)Curing
accelerator (C1) DBU-type tetraphenylborate salt 0.5 0.5 0.5 0.5
0.5 0.5 (D)Inorganic filler (D1) Treated silica (KBM573, 12 .mu.m)
1850 1150 2300 (D2) Treated silica (KBM403, 12 .mu.m) 1850 (D3)
Treated silica (KBM573, 0.8 .mu.m) 1850 (D4) Silica (12 .mu.m) 1850
(E)Ester compound (E1) Montanic acid ester compound 11 3 3 3 3 3
(F)Other additives (F1) Adhesion imparting agent 1 1 1 1 1 1 (F2)
Carbon black 1 1 1 1 1 1 Evaluation item Sheet-like shape Favorable
Favorable Failed Failed Failed Failed Glass-transition temperature
[Tg] (.degree. C.) 220 220 to be to be to be to be Linear expansion
coefficient 1 (ppm/.degree. C.) 4.5 5.2 molded molded molded molded
Filling failure (Yes No) No No into into into into Warpage amount
(mm) <1 20 sheet- sheet- sheet- sheet- Reliability test Presence
or absence of peeling, NG NG like like like like crack (IR reflow)
shape shape shape shape (NA) (NA) (NA) (NA)
* * * * *