U.S. patent application number 09/829229 was filed with the patent office on 2001-10-18 for bonding layer method in a semiconductor device.
Invention is credited to Yukawa, Masahiko.
Application Number | 20010031545 09/829229 |
Document ID | / |
Family ID | 16841482 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010031545 |
Kind Code |
A1 |
Yukawa, Masahiko |
October 18, 2001 |
Bonding layer method in a semiconductor device
Abstract
A semiconductor chip is bonded on a radiator plate consisting of
copper material with interposition of a bonding layer having a
total thickness of 80 .mu.m comprising a laminated structure
including a thermoplastic film bonding layer 12a having a thickness
of 50 .mu.m and a paste-based bonding layer 12b having a thickness
of 30 .mu.m. For example, butadiene-modified polyolefin-based
adhesive resin mixed with alumina fine power is used as material of
the thermoplastic film bonding layer 12a, and, for example,
silicone rubber-modified epoxy-based adhesive resin mixed with
silver powder is used as material of the paste-based bonding layer
12b. There is thus provided a semiconductor device having a
semiconductor chip bonded on a radiator plate with interposition of
a bonding layer, wherein stress concentration caused in the bonding
layer is relaxed and heat dissipation performance is maintained and
thus the reliability in endurance is high, and a method for
manufacturing the semiconductor device.
Inventors: |
Yukawa, Masahiko; (Kanagawa,
JP) |
Correspondence
Address: |
SONNENSCHEIN NATH & ROSENTHAL
Sears Tower
Wacker Drive Station
P.O. Box 061080
Chicago
IL
60606-1080
US
|
Family ID: |
16841482 |
Appl. No.: |
09/829229 |
Filed: |
April 9, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09829229 |
Apr 9, 2001 |
|
|
|
09369282 |
Aug 6, 1999 |
|
|
|
Current U.S.
Class: |
438/584 ;
257/E23.087 |
Current CPC
Class: |
H01L 2924/1517 20130101;
H01L 2924/15311 20130101; H01L 2224/73269 20130101; H01L 23/3128
20130101; H01L 2224/32245 20130101; H01L 2224/50 20130101; H01L
2924/1532 20130101; H01L 23/42 20130101; H01L 2924/15153
20130101 |
Class at
Publication: |
438/584 |
International
Class: |
H01L 021/20 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 1998 |
JP |
P10-226201 |
Claims
What is claimed is:
1. A semiconductor device having a semiconductor chip bonded on a
radiator plate with interposition of a bonding layer, wherein said
bonding layer comprises a laminated structure including a
thermoplastic film bonding layer and a paste-based bonding
layer.
2. A semiconductor device as claimed in claim 1, wherein the total
thickness of said thermoplastic film bonding layer and said
paste-based bonding layer is 50 to 150 .mu.m.
3. A semiconductor device as claimed in claim 1, wherein said
thermoplastic film bonding layer is modified or blended with a
rubber-based material.
4. A semiconductor device as claimed in claim 1, wherein said
thermoplastic film bonding layer is mixed with ceramic fine powder
or metal powder.
5. A semiconductor device as claimed in claim 1, wherein said
paste-based bonding layer comprises a resin mixed with fine powder
filler.
6. A semiconductor device as claimed in claim 5, wherein said
paste-based bonding layer is formed of epoxy-based adhesive resin,
and said epoxy-based adhesive resin is modified or blended with a
rubber-based material.
7. A method for manufacturing a semiconductor device comprising: a
step for coating a paste-based bonding layer on the back side of a
semiconductor chip; a step for bonding a thermoplastic film bonding
layer on a radiator plate; and a step for heat-press-bonding said
paste-based bonding layer coated on the back side of said
semiconductor chip and said thermoplastic film bonding layer bonded
on said radiator plate together.
8. A method for manufacturing a semiconductor device comprising: a
step for bonding a thermoplastic film bonding layer on a radiator
plate; a step for coating a paste-based bonding layer on said
thermoplastic film bonding layer; and a step for press-bonding a
semiconductor chip on said paste-based bonding layer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a semiconductor device and a
manufacturing method thereof and more particularly to a
semiconductor device having a semiconductor chip bonded on a
radiator plate with interposition of a bonding layer.
[0003] 2. Description of the Related Art
[0004] It has been required that consumer appliances are made
compact and the requirement has called for one chip structuring of
a semiconductor device or high density mounting of a semiconductor
device, and thus area array packages such as ball grid array, in
which external connecting terminals are arranged in the form of
two-dimensional area (referred to simply as "BGA" hereinafter), and
land grid array (referred to simply as "LGA" hereinafter) have been
proposed and practically used to satisfy the requirement for
multi-pin semiconductor.
[0005] As a related area package, tape BGA (Tape-BFA, referred to
simply as "T-BGA" hereinafter), in which TAB (Tape Automated
Bonding) is used as interconnection technique, is described
referring to FIG. 2.
[0006] For example, a semiconductor chip 44 is bonded on a radiator
plate 40 consisting of copper material with interposition of a
paste bonding layer 42. Many electrode pads 46 are formed on the
surface of the semiconductor chip 44.
[0007] On the circumference of the radiator plate 40 surrounding
the semiconductor chip 44, a stiffener 50 is bonded with
interposition of a bonding layer 48. On the stiffener 50, many
external connecting terminals 54 having a ball-shaped end
respectively are arranged dispersedly in the form of array.
[0008] These many external connecting terminals 54 are connected to
the electrode pads on the semiconductor chip 44 with interposition
of respective inner leads 56. These many external connecting
terminals 54 are covered with an insulating film 58 excepting the
ball-shaped ends and insulated stably each other. As described
herein above, the external connecting terminals 54, inner leads 56,
and insulating film 58 constitute a wiring pattern 60 for
connecting the electrode pads of the semiconductor chip 44 to the
external.
[0009] The semiconductor chip 44 bonded on the radiator plate 40
with interposition of the paste bonding layer 42 and the inner
leads 56 connected to the electrode pads 46 are covered with
sealing resin 62, this is so-called resin sealing.
[0010] As described herein above, in the T-BGA, because many
external connecting terminals 54 are arranged dispersedly in the
form of array on the stiffener 50 surrounding the semiconductor
chip 44, the package size of a T-BGA is made small even if the
pitch of the external connecting terminals 54 of the semiconductor
device having many pins is relatively large, for example, 1.0 mm or
0.27 mm, therefore this structure is effective for high density
mounting.
[0011] Further, the semiconductor chip 44 is bonded directly on the
radiator plate 40 with interposition of the paste bonding layer 42,
and therefore heat generated from the semiconductor element during
operation is easily dissipated, thus this structure is also
effective for low heat resistance packaging.
[0012] However, in the above-mentioned T-BGA, the thermal expansion
coefficient of the semiconductor chip 44 is approximately 3
ppm/.degree. C. and the thermal expansion coefficient of the
radiator plate 40 consisting of copper material is approximately 17
ppm/.degree. C., the large difference in the thermal expansion
coefficient between both components causes the stress concentration
on the paste bonding layer 42 between the semiconductor chip 44 and
the radiator plate 40, for example, when the semiconductor device
is subjected to a thermal cycle test (referred to simply as T/C
test hereinafter), in which the temperature of the T-BGA is varied
cyclically, the bonding strength of the paste bonding layer 42 is
decreased to cause cracking or separation occasionally at the
end.
[0013] As described herein above, though the semiconductor device
is excellent in heat dissipation initially as it is fabricated,
after T/C test, the bonding strength of the paste bonding layer 42
which has been subjected to stress concentration is decreased, and
good contact between the semiconductor chip 44 and the radiator
plate 40 is deteriorated to result in significantly reduced heat
dissipation, and thus the reliability in endurance becomes poor
disadvantageously.
[0014] Not only T-BGA but also semiconductors of other types as
long as a bonding layer is provided between a semiconductor chip
and a radiator plate or a die pad consisting of copper material are
involved generally in the problem.
[0015] The present invention has been accomplished to solve the
above-mentioned problem, and the object of the present invention is
to provide a semiconductor device having a semiconductor chip
bonded on a radiator plate with interposition of a bonding layer in
which stress concentration caused in the bonding layer is relaxed
to maintain the heat dissipation performance and which is excellent
in reliability in endurance and a method for manufacturing
thereof.
[0016] The inventors of the present invention examined the
reduction of stress concentration caused in a bonding layer between
bonded bodies formed of different materials due to the difference
in thermal expansion coefficient between these materials to solve
the above-mentioned problem.
[0017] In general, sufficiently thick thickness of a bonding layer
is required to relax stress concentration on the bonding layer to
be provided between a semiconductor chip and a radiator plate which
have the different thermal expansion coefficient each other.
However, it is difficult to form an even bonding layer having a
sufficient thickness with a single layer of a related paste-based
bonding layer, and a bonding layer having the sufficiently thick
thickness can not be realized.
[0018] To secure an even bonding layer having a thickness
sufficient for the bonding layer to relax stress concentration
caused on the bonding layer, the inventors tried to use a
thermoplastic film bonding layer instead of paste-based bonding
layer. In this case, though it was easily achieved to form an even
bonding layer having a sufficient and necessary thickness, the
bonding layer was involved in the problem of blistering in at least
any one of interfaces between a semiconductor chip and the
thermoplastic film bonding layer or a radiator plate and the
thermoplastic film bonding layer when the thermoplastic film
bonding layer placed between a semiconductor chip of a hard
material and a radiator plate of a hard material was press-bonded
together. In detail, though no blistering was not caused when a
thermoplastic film bonding layer was bonded on a semiconductor chip
or a radiator plate, however, it was very difficult to prevent
blistering when a radiator plate or a semiconductor chip was
press-bonded on the thermoplastic film bonding layer bonded on the
semiconductor chip or the radiator plate. The existence of the
blister resulted in reduced bonding strength and reduced heat
dissipation performance of the bonding layer.
[0019] Experiments were repeated to find a bonding layer for
forming an even bonding layer having a necessary and sufficient
thickness to relax stress concentration by a method in which
blistering was prevented so as not to cause reduction of bonding
strength and reduction of heat dissipation performance. As the
result, the semiconductor device and the method for manufacturing
thereof in accordance with the present invention has been
accomplished.
SUMMARY OF THE INVENTION
[0020] In detail, a semiconductor device in accordance with one
aspect of the present invention is a semiconductor device having a
semiconductor chip bonded on a radiator plate with interposition of
a bonding layer, wherein the bonding layer comprises a laminated
structure including a thermoplastic film bonding layer and a
paste-based bonding layer.
[0021] In the semiconductor device in accordance with one aspect of
the present invention, because the laminated structure including
the thermoplastic film bonding layer and the paste-based bonding
layer is employed as the bonding layer for bonding the
semiconductor chip on the radiator plate, an even bonding layer
having a necessary and sufficient thickness is formed, and
blistering, which causes reduction of bonding strength and
reduction of heat dissipation of the bonding layer, is
prevented.
[0022] In other words, the thermoplastic film bonding layer is
served to secure the necessary and sufficient thickness of the
bonding layer and to secure the evenness of the bonding layer, and
on the other hand, the paste-based bonding layer formed of soft
material which is provided on the one side of the thermoplastic
film bonding layer is served to prevent blistering when the bonding
layer is press-bonded together with the thermoplastic film bonding
layer.
[0023] The semiconductor device in accordance with another aspect
of the present invention is a semiconductor device described in the
above-mentioned claim 1, wherein the total thickness of the
thermoplastic film bonding layer and the paste-based bonding layer
is in a range from 50 to 150 .mu.m, and the stress concentration
suppression effect is thereby improved while the heat dissipation
effect of the bonding layer having the two layer structure is
maintained.
[0024] In detail, the total thickness of the thermoplastic film
bonding layer and the paste-based bonding layer thinner than 50
.mu.m results in reduced stress concentration suppression effect on
the bonding layer having the two layer structure though the heat
dissipation effect is improved, for example, the excellent contact
between the semiconductor chip and the radiator plate is
deteriorated and the heat dissipation performance is decreased
after T/C testing, and the reliability in endurance therefore
becomes poor. On the other hand, the total thickness of the
thermoplastic film bonding layer and the paste-based bonding layer
thicker than 150 .mu.m results in reduced heat dissipation effect
though the stress concentration suppression effect on the bonding
layer having the two layer structure is improved. Accordingly, the
total thickness of the thermoplastic film bonding layer and the
paste-based bonding layer of 50 to 150 .mu.m is preferable to
improve the stress concentration suppression effect while the heat
dissipation effect of the bonding layer having the two layer
structure is improved.
[0025] The thickness of the thermoplastic film bonding layer is
preferably in a range form 20 to 100 .mu.m and the thickness of the
paste-based bonding layer is preferably in a range from 10 to 70
.mu.m while the total thickness of the bonding layer having the two
layer structure is in a range from 50 to 150 .mu.m.
[0026] The semiconductor device in accordance with another aspect
of the present invention is a semiconductor described in the
above-mentioned claim 1, wherein the thermoplastic film bonding
layer is modified or blended with rubber-based material. For
example, polyolefin-based or polyimide-based thermoplastic resin is
modified or blended with silicone rubber, butadiene rubber,
urethane rubber, or acrylic rubber, and the film-like thermoplastic
resin bonding layer is thereby rendered soft and low in the elastic
modulus, thus the larger stress concentration relaxation effect is
brought about with the thinner thickness. Particularly the
thermoplastic film bonding layer having the elastic modulus of 1
GPa or lower at a room temperature and the elastic modulus of 3 GPa
or lower at -25.degree. C. is more effective in stress
concentration suppression.
[0027] The semiconductor device in accordance with another aspect
of the present invention is a semiconductor described in the
above-mentioned claim 1, wherein ceramic fine powder or metal
powder is mixed in the thermoplastic film bonding layer. The
ceramic fine powder or metal power is served to improve the thermal
conductivity of the thermoplastic film bonding layer, and thereby
brings about the more improved heat dissipation performance.
Examples of ceramic fine powder include, for example, fine powder
of alumina, silica, and silicon nitride, and examples of metal
powder include, for example, silver powder and aluminum powder.
[0028] Further, the semiconductor device in accordance with another
aspect of the present invention is the above-mentioned
semiconductor, wherein the paste-based bonding layer is mixed with
fine powder filler. For example, the fine powder filler such as
silver powder or silica powder is mixed in epoxy resin or silicone
resin, and thereby improves the bonding strength and thermal
conductivity of the paste-based bonding layer.
[0029] Further, the semiconductor device in accordance with another
aspect of the present invention is a semiconductor device described
above, wherein the paste-based bonding layer is formed of
epoxy-based adhesive resin, and the epoxy-based adhesive resin is
modified or blended with rubber-based material. For example,
epoxy-based adhesive resin is modified or blended with silicone
rubber, butadiene rubber, urethane rubber, or acrylic rubber, then
the elastic modulus is thereby reduced, and such epoxy-based
adhesive resin exhibits the more stress concentration relaxation
effect with the thinner thickness. Particularly, the paste-based
bonding layer having an elastic modulus of 1 GPa or lower at a room
temperature exhibits the marked stress concentration relaxation
effect.
[0030] Further, a method for manufacturing a semiconductor device
in accordance with another aspect of the present invention
comprises a step for coating a paste-based bonding layer on the
back side of the semiconductor chip, a step for bonding a
thermoplastic film bonding layer on a radiator plate, and a step
for heat-press-bonding the paste-based bonding layer coated on the
back side of the semiconductor chip and the thermoplastic film
bonding layer bonded on the radiator plate together.
[0031] In the method for manufacturing a semiconductor device in
accordance with another aspect of the present invention as
described herein above, the paste-based bonding layer coated on the
back side of the semiconductor chip and the thermoplastic film
bonding layer bonded on the radiator plate are heat-press-bonded
together to thereby form an even bonding layer having a necessary
and sufficient thickness comprising the laminated structure
including the thermoplastic film bonding layer and the paste-based
bonding layer. In this case, blistering, which causes reduction of
bonding strength and reduction of heat dissipation performance of
the bonding layer, is prevented because the thermoplastic film
bonding layer is bonded on the radiator plate and then the exposed
side is heat-press-bonded to the paste-based bonding layer of soft
material, differently from the case that the bonding layer is
placed directly between the semiconductor chip and the radiator
plate of hard material and press-bonded together.
[0032] A method for manufacturing a semiconductor device in
accordance with another aspect of the present invention comprises a
step for bonding a thermoplastic film bonding layer on a radiator
plate, a step for coating a paste-based bonding layer on the
thermoplastic film bonding layer, and a step for press-bonding the
semiconductor chip on the paste-based bonding layer.
[0033] In the method for manufacturing a semiconductor in
accordance with another aspect of the present invention, as
described herein above, the paste-based bonding layer is bonded on
the thermoplastic film bonding layer bonded on the radiator plate
to thereby form an even bonding layer having a necessary and
sufficient thickness comprising the laminated structure including
the thermoplastic film bonding layer and the paste-based bonding
layer. Because the paste bonding layer of soft material is coated
on the exposed surface of the thermoplastic film bonding layer
after the thermoplastic film bonding layer has been bonded on the
radiator plate, blistering, which causes reduction of bonding
strength and reduction of heat dissipation performance of the
bonding layer, is prevented, diffidently from the case that the
bonding layer is placed directly between the semiconductor chip and
the radiator plate of hard material and then press-bonded
together.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a schematic cross sectional view for illustrating
T-BGA in accordance with one embodiment of the present
invention.
[0035] FIG. 2 is a schematic cross sectional view for illustrating
the related T-BGA.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] The embodiment of the present invention will be described in
detail hereinafter with reference to the attached drawings.
[0037] FIG. 1 is a schematic cross sectional view for illustrating
a T-BGA in accordance with one embodiment of the present
invention.
[0038] A semiconductor chip 14 is bonded on a radiator plate 10
consisting of, for example, copper material with interposition of a
bonding layer 12 having a total thickness of 80 .mu.m comprising
two layer structure of a thermoplastic film bonding layer 12a
having a thickness of 50 .mu.m and a paste bonding layer 12b having
a thickness of 30 .mu.m. A plurality of electrode pads 16 are
formed on the surface of the semiconductor chip 14. For example, a
polyolefin-based adhesive resin modified with butadiene rubber
mixed with alumina fine powder is used as the material of the
thermoplastic film bonding layer 12a, and, for example, a
epoxy-based adhesive resin modified with silicone rubber mixed with
silver powder is used as the material of the paste-based bonding
layer 12b.
[0039] A stiffener 20 is bonded on the radiator plate 10
surrounding the semiconductor chip 14 with interposition of a
bonding layer 18. A plurality of external connecting terminals 24
having a ball-shaped end are arranged dispersedly in the form of
array on the stiffener 20 with interposition of a bonding layer
22.
[0040] The plurality of external connecting terminals 24 are
connected to the electrode pads 16 provided on the surface of the
semiconductor chip 14 with interposition of respective inner leads
26. The plurality of external connecting terminals 24 are covered
with an insulating film 28 excepting the ball-shaped ends, and are
insulated stably each other. The plurality of external connecting
terminals 24 having a ball-shaped end, inner leads 26 connected to
the respective external connecting terminals 24, and the insulating
film 28 which covers these external connecting terminals 24
excepting the ball-shaped ends constitute a wiring pattern 30 for
connecting the electrode pads 16 of the semiconductor 14 to the
external.
[0041] The semiconductor chip 14, which is bonded on the radiator
plate 10 with interposition of the bonding layer 12 comprising the
laminated structure including the thermoplastic film bonding layer
12a and the paste bonding layer 12b, and the inner leads 26
connected to the respective electrode pads 16 are covered with the
sealing resin 32 and resin sealed.
[0042] Next, the first fabrication process of the T-BGA is
described.
[0043] First, the wiring pattern 30 comprising the plurality of
external connecting terminals 24 having a ball-shaped end, the
inner leads 26 connected to the respective external connecting
terminals 24, and the insulating film 28, which covers the
respective connecting terminals 24 excepting ball-shaped ends, is
heat-press-bonded on the stiffener 20 with interposition of the
bonding layer 22. The plurality of external connecting terminals 24
having a ball-shaped end are arranged dispersedly in the form of
array on the stiffener 20 as described herein above.
[0044] Next, the semiconductor chip 14 is bonded on the radiator
plate 10 consisting of copper material at a predetermined position
with interposition of the bonding layer 12 comprising the laminated
structure including the thermoplastic film bonding layer 12a and
the paste-based bonding layer 12b. In this case, two methods are
employable.
[0045] In one method of the two, the paste-based bonding layer 12b
consisting of epoxy-based adhesive resin modified with silicone
rubber having a thickness of 30 .mu.m is coated on the back side of
the semiconductor chip 14. Further, the thermoplastic film bonding
layer 12a consisting of polyolefin-based adhesive resin modified
with butadiene rubber having a thickness of 50 .mu.m is bonded on
the radiator plate 10 at a predetermined position. Subsequently,
the paste-based bonding layer 12b coated on the based side of the
semiconductor 14 and the thermoplastic film bonding layer 12a
bonded on the radiator plate 10 are heat-press-bonded together.
[0046] In the other method of the two, the thermoplastic film
bonding layer 12a consisting of polyolefin-based adhesive resin
modified with butadiene rubber having a thickness of 50 .mu.m is
bonded on the radiator plate 10 at a predetermined position.
Subsequently, the paste-based bonding layer 12b consisting of
epoxy-based adhesive resin modified with silicone rubber having a
thickness of 30 .mu.m is coated on the thermoplastic film bonding
layer 12a. Further, the semiconductor chip 14 is press-bonded on
the paste-based bonding layer 12b.
[0047] Next, the stiffener 20 on which the wiring pattern 30 has
been press-bonded is aligned and then bonded on the radiator plate
10 surrounding the semiconductor chip 14 with interposition of the
bonding layer 18. Subsequently, the inner leads 26 of the wiring
pattern 30 are connected to the electrode pads 16 on the surface of
the semiconductor chip 14. As described herein above, the electrode
pads 16 on the surface of the semiconductor chip 14 are connected
to the external connecting terminals 24 by way of the inner leads
26 by inner lead bonding.
[0048] Next, the semiconductor chip 14 bonded on the radiator plate
10 with interposition of the bonding layer 12 comprising the
laminated structure including the thermoplastic film bonding layer
12a and the paste-based bonding layer 12b and the inner leads 26
connected to the respective electrode pads 16 are covered with the
sealing resin 32 and resin sealed. Thus the T-BGA shown in FIG. 1
is fabricated.
[0049] Next, the second fabrication method of T-BGA shown in FIG. 1
is described.
[0050] First, the wiring pattern 30 comprising the plurality of
external connecting terminals 24 having a ball-shaped end, the
inner leads 26 connected to the respective external connecting
terminals 24, and the insulating film 28, which covers the
respective connecting terminals 24 excepting ball-shaped ends, is
press-bonded on the stiffener 20 with interposition of the bonding
layer 22. The plurality of external connecting terminals 24 having
a ball-shaped end are arranged dispersedly in the form of array on
the stiffener 20 as described herein above.
[0051] Next, the inner leads 26 of the wiring pattern 3C which is
press-bonded on the stiffener 20 is connected to the electrode pads
16 on the surface of the semiconductor chip 14 by inner lead
bonding. As described herein above, the electrode pads 16 on the
surface of the semiconductor chip 14 are connected to the
respective external connecting terminals 24 by way of the
respective inner leads 26.
[0052] Next, the semiconductor chip 14 is bonded on the radiator
plate 10 at a predetermined position with interposition of the
bonding layer 12 comprising the laminated structure including the
thermoplastic film bonding layer 12a and the paste-based bonding
layer 12b, and the stiffener 20 is bonded on the radiator plate 10
surrounding the semiconductor chip 14 with interposition of the
bonding layer 18. Two methods are employable also in this case.
[0053] In one method, the paste-based bonding layer 12b consisting
of epoxy-based adhesive resin modified with silicone rubber having
a thickness of 30 .mu.m is coated on the back side of the
semiconductor chip 14. The thermoplastic film bonding layer 12a
consisting of polyolefin-based modified with butadiene rubber
having a thickness of 50 .mu.m is bonded on the radiator plate 10
at the position where the semiconductor chip 14 is to be mounted,
and the bonding layer 18 is coated on the radiator plate 10
surrounding the place where the semiconductor chip 14 is to be
mounted. Subsequently, the paste-based bonding layer 12b coated on
the back side of the semiconductor chip 14 and the thermoplastic
film bonding layer 12a bonded on the radiator plate 10 are
heat-press-bonded together, and the stiffener 20 is press-bonded on
the bonding layer 18 coated on the radiator plate 10.
[0054] In the other method, the thermoplastic film bonding layer
12a consisting of polyolefin-based adhesive resin modified with
butadiene having a thickness of 50 .mu.m is bonded on the radiator
plate 10 at the place where the semiconductor chip 14 is to be
mounted. Subsequently, the paste-based bonding layer 12b consisting
of epoxy-based adhesive resin modified with silicone rubber having
a thickness of 30 .mu.m is coated on the thermoplastic film bonding
layer 12a. The semiconductor chip 14 is thereafter press-bonded on
the paste-based bonding layer 12b coated on the thermoplastic film
bonding layer 12a, and the stiffener 20 is press-bonded on the
bonding layer 18 coated on the radiator plate 10.
[0055] Next, the semiconductor chip 14 bonded on the radiator plate
10 with interposition of the bonding layer 12 comprising the
laminated structure including the thermoplastic film bonding layer
12a and the paste-based bonding layer 12b and the inner leads 26
connected to the respective electrode pads of the semiconductor
chip 14 are covered with the sealing resin 32 and resin sealed.
Thus the T-BGA shown in FIG. 1 is fabricated.
[0056] Next, the T/C test result on the T-BGA in accordance with
the present embodiment shown in FIG. 1 is described.
[0057] In the T/C test, the high temperature side temperature was
set to 125.degree. C. and the low temperature side temperature was
set to -55.degree. C. Four sets of conditions for thermal cycling
namely the number of cycles of 200, 400, 600, and 1000 were used.
Ten test T-BGAs shown in FIG. 1 were fabricated and these Ten
T-BGAs were subjected to the test. For comparison, Ten related
T-BGAs as shown in FIG. 2 were fabricated and these related 10
T-BGAs were also subjected to the same T/C test.
[0058] The number of defectives caused in the laminated structure
including the thermoplastic film bonding layer 12a and the
paste-based bonding layer 12b of the T-BGAs in accordance with the
present embodiment shown in FIG. 1 and the number of defectives
caused in the paste-based bonding layer 42 of the related T-BGAs
shown in FIG. 2 in the T/C test are shown in Table 1.
1TABLE 1 The number of defectives Thermal cycles 200 400 600 1000
T-BGA according to the 0/10 0/10 0/10 0/10 present embodiment
Related T-BGA 0/10 2/10 10/10 --
[0059] As obviously shown in the T/C test result in Table 1, zero
test piece out of 10 T-BGA in accordance with the present invention
shown in FIG. 1 are defective due to cracking or separation in the
bonding layer 12 comprising laminated structure including the
thermoplastic film bonding layer 12a and the paste-based bonding
layer 12b after 1000 repeated thermal cycles, that is, no defective
was caused.
[0060] On the other hand, in the case of the related T-BGAs shown
in FIG. 2, though no defect was caused after 200 repeated thermal
cycles, two defectives were caused after 400 repeated thermal
cycles, and 10 defectives were caused after 600 repeated thermal
cycles, that is, all the test pieces were defective.
[0061] As described herein above, according to the present
embodiment, by heat-press-bonding the paste-based bonding layer 12b
consisting of soft material having a thickness of 30 .mu.m coated
on the back side of the semiconductor chip 14 and the thermoplastic
film bonding layer 12a having a thickness of 50 .mu.m bonded on the
radiator plate 10 together or by press-bonding the semiconductor
chip 14 on the paste-based bonding layer 12b having a thickness of
30 .mu.m which has been formed by coating soft paste-based bonding
material on the thermoplastic film bonding layer 12a having a
thickness of 50 .mu.m bonded on the radiator plate 10, the bonding
layer 12 comprising the laminated structure including a total
thickness of 80 .mu.m, which satisfies the necessary and sufficient
condition, is formed evenly, and blistering which will cause
reduction of bonding strength of the bonding layer and reduction of
heat dissipation is prevented, the bonding structure described
herein above is effective to relax stress concentration caused in
the bonding layer 12 comprising the two layer structure and to
maintain excellent heat dissipation performance, and thus high
reliability in endurance is realized.
[0062] In the above-mentioned embodiment, the bonding layer 12
comprising the laminated structure including the thermoplastic film
bonding layer 12a and the paste-based bonding layer 12b having a
total thickness of 80 .mu.m is used, however the total thickness of
the bonding layer 12 comprising the two layer thickness is by no
means limited to this value, for example, any bonding layer 12 may
be used to improve the stress concentration preventing effect while
maintaining the heat dissipating effect on the bonding layer 12
comprising the two layer structure as long as the total thickness
is, for example, in a range from 50 .mu.m to 150 .mu.m.
[0063] The bonding layer 12 exhibits the maximized stress
concentration relaxing effect with a thinner thickness by employing
polyolefin-based adhesive resin modified with butadiene rubber as
the material of the thermoplastic film bonding layer 12a to form
the bonding layer of a soft thermoplastic resin film by using
polyolefin-based adhesive resin modified with butadiene rubber as
the material of the thermoplastic film bonding layer 12a so that
the bonding layer is formed of soft thermoplastic film resin having
low elastic modulus. Further, polyolefin-based adhesive resin
modified with butadiene rubber contains alumina fine powder so that
the thermal conductivity is increased and the heat dissipation
performance is improved.
[0064] In the above-mentioned present embodiment, the thermoplastic
resin of polyolefin-based adhesive resin was used as the material
of the thermoplastic film bonding layer 12a, however the material
of the thermoplastic film bonding layer 12a is no by means limited
to this resin, for example, other thermoplastic resin such as
polyimide may be used. The thermoplastic resin which is modified
with butadiene rubber is used in the above-mentioned present
embodiment, however other polymers such as silicone rubber,
urethane rubber, or acrylic rubber may be used for modification or
blending. Further, fine powder of ceramics such as silica or
silicon nitride, or metal fine power such as silver power or
aluminum powder may be mixed instead of alumina fine powder.
[0065] The bonding strength and thermal conductivity of the
paste-based bonding layer 12b are increased by using epoxy-based
adhesive resin mixed with silver powder as the material of the
paste-based bonding layer 12b. Because the elastic modulus is
decreased by modifying epoxy-based adhesive resin with silicone
rubber, the bonding layer exhibits significant stress concentration
relaxing effect with a thinner thickness.
[0066] In the above-mentioned embodiment, epoxy-based adhesive
resin mixed with silver powder is used as the material of the
paste-based bonding layer 12b, however the material of the
paste-based bonding layer 12b is by no means limited to this resin,
for example, silicone-based adhesive resin may be used instead of
epoxy-based adhesive resin. Further, fine powder filler such as
silica powder or alumina powder may be used instead of silver
powder. Epoxy-based adhesive resin is modified with silicone rubber
in the above-mentioned embodiment, however for example, butadiene
rubber, urethane rubber, or acrylic rubber may be used for
modification or blending.
[0067] As described herein above, according to the semiconductor
device and the fabrication method thereof in accordance with the
present invention, the present invention exhibits the following
effects.
[0068] In detail, according to the semiconductor device in
accordance with the claim 1, because the laminated structure
including the thermoplastic film bonding layer and the paste-based
bonding layer is employed as the bonding layer for bonding the
semiconductor chip on the radiator plate, an even bonding layer
having a necessary and sufficient thickness is formed, and
blistering, which causes reduction of bonding strength and
reduction of heat dissipation of the bonding layer, is prevented,
further the stress concentration caused in the bonding layer is
relaxed while the heat dissipation performance is maintained, and
thus high reliability in endurance is obtained.
[0069] According to the semiconductor device in accordance with
claim 2, the total thickness of the thermoplastic film bonding
layer and the paste-based bonding layer is in a range from 50 to
150 .mu.m, and the stress concentration suppression effect is
thereby improved while the heat dissipation effect of the bonding
layer having the two layer structure is maintained.
[0070] According to the semiconductor device in accordance with
claim 3, the thermoplastic film bonding layer is modified or
blended with rubber-based material, and the film-like thermoplastic
resin bonding layer is thereby rendered soft and low in the elastic
modulus, thus the larger stress concentration relaxation effect is
brought about with the thinner thickness.
[0071] According to the semiconductor device in accordance with
claim 4, ceramic fine powder or metal powder is mixed in the
thermoplastic film bonding layer. The ceramic fine powder or metal
power is served to improve the thermal conductivity of the
thermoplastic film bonding layer, and thereby brings about the more
improved heat dissipation performance.
[0072] According to the semiconductor device in accordance with
claim 5, the paste-based bonding layer is mixed with fine powder
filler, and thereby improves the bonding strength and thermal
conductivity of the paste-based bonding layer.
[0073] According to the semiconductor device in accordance with
claim 6, the epoxy-based adhesive resin is modified or blended with
rubber-based material, the elastic modulus is thereby reduced, and
such epoxy-based adhesive resin exhibits the more stress
concentration relaxation effect with the thinner thickness.
[0074] According the method for manufacturing a semiconductor
device in accordance with claim 7, the paste-based bonding layer
coated on the back side of the semiconductor chip and the
thermoplastic film bonding layer bonded on the radiator plate are
heat-press-bonded together to thereby form an even bonding layer
having a necessary and sufficient thickness comprising the
laminated structure including the thermoplastic film bonding layer
and the paste-based bonding layer. Further, blistering, which
causes reduction of bonding strength and reduction of heat
dissipation performance of the bonding layer, is prevented because
the thermoplastic film bonding layer is bonded on the radiator
plate and then the exposed side is heat-press-bonded on the
paste-based bonding layer of soft material.
[0075] According to the method for manufacturing a semiconductor
device in accordance with claim 8, the paste-based bonding layer is
bonded on the thermoplastic film bonding layer bonded on the
radiator plate to thereby form an even bonding layer having a
necessary and sufficient thickness comprising the laminated
structure including the thermoplastic film bonding layer and the
paste-based bonding layer. Further, because the paste bonding layer
of soft material is coated on the exposed surface of the
thermoplastic film bonding layer after the thermoplastic film
bonding layer has been bonded on the radiator plate, blistering,
which causes reduction of bonding strength and reduction of heat
dissipation performance of the bonding layer, is prevented,
* * * * *