U.S. patent application number 11/365674 was filed with the patent office on 2006-07-06 for method for manufacturing semiconductor device having a pair of heat sinks.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Shusaku Nakazawa, Takanori Teshima.
Application Number | 20060145335 11/365674 |
Document ID | / |
Family ID | 34277747 |
Filed Date | 2006-07-06 |
United States Patent
Application |
20060145335 |
Kind Code |
A1 |
Teshima; Takanori ; et
al. |
July 6, 2006 |
Method for manufacturing semiconductor device having a pair of heat
sinks
Abstract
A semiconductor device includes a heater element; a first heat
sink disposed on one side of the heater element; a second heat sink
disposed on the other side of the heater element; and a resin mold
for molding the heater element and the first and second heat sinks.
The first heat sink includes a first heat radiation surface, which
is disposed opposite to the heater element and exposed from the
resin mold. The second heat sink includes a second heat radiation
surface, which is disposed opposite to the heater element and
exposed from the resin mold. The first and second heat radiation
surfaces have a degree of parallelism therebetween equal to or
smaller than 0.2 mm.
Inventors: |
Teshima; Takanori;
(Okazaki-city, JP) ; Nakazawa; Shusaku; (Obu-city,
JP) |
Correspondence
Address: |
POSZ LAW GROUP, PLC
12040 SOUTH LAKES DRIVE
SUITE 101
RESTON
VA
20191
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
34277747 |
Appl. No.: |
11/365674 |
Filed: |
March 2, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10916551 |
Aug 12, 2004 |
7049688 |
|
|
11365674 |
Mar 2, 2006 |
|
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Current U.S.
Class: |
257/718 ;
257/717; 257/E23.092; 257/E25.016; 438/117 |
Current CPC
Class: |
H01L 2924/01074
20130101; H01L 2924/12042 20130101; H01L 24/32 20130101; H01L
2224/48472 20130101; H01L 2924/1305 20130101; H01L 2924/01005
20130101; H01L 24/48 20130101; H01L 2224/48091 20130101; H01L
25/072 20130101; H01L 2924/01013 20130101; H01L 2924/01042
20130101; H01L 2924/01006 20130101; H01L 2224/73265 20130101; H01L
2924/01029 20130101; H01L 2924/01019 20130101; H01L 2224/45124
20130101; H01L 2224/32245 20130101; H01L 2924/1305 20130101; H01L
2924/1815 20130101; H01L 2224/45144 20130101; H01L 2224/33181
20130101; H01L 2924/01033 20130101; H01L 2924/01082 20130101; H01L
2224/48247 20130101; H01L 2224/73265 20130101; H01L 2224/48472
20130101; H01L 2224/45144 20130101; H01L 23/4334 20130101; H01L
24/45 20130101; H01L 2224/73215 20130101; H01L 2924/181 20130101;
H01L 2224/33 20130101; H01L 24/33 20130101; H01L 2224/45124
20130101; H01L 2924/12042 20130101; H01L 2924/13055 20130101; H01L
2924/01043 20130101; H01L 2924/181 20130101; H01L 2924/00012
20130101; H01L 2924/00014 20130101; H01L 2224/48247 20130101; H01L
2924/00 20130101; H01L 2924/00014 20130101; H01L 2224/48247
20130101; H01L 2224/32245 20130101; H01L 2924/00014 20130101; H01L
2224/48091 20130101; H01L 2224/48472 20130101; H01L 2224/48091
20130101; H01L 2924/01079 20130101; H01L 2924/00 20130101; H01L
2924/00 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
257/718 ;
438/117; 257/717 |
International
Class: |
H01L 23/34 20060101
H01L023/34; H01L 21/48 20060101 H01L021/48 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 2003 |
JP |
2003-324585 |
May 19, 2004 |
JP |
2004-148933 |
Claims
1-5. (canceled)
6. A method for manufacturing a semiconductor device, the method
comprising the steps of: sandwiching both sides of a heater element
by first and second heat sinks so that the heat sinks and the
heater element are thermally connected; molding the heater element
together with the first and second heat sinks with a resin mold in
such a manner that at least one of the first and second heat sinks
is embedded in the resin mold; and removing a part of the embedded
one of the first and second heat sinks together with the resin mold
so that the embedded one of the first and second heat sinks is
exposed from the resin mold.
7. The method according to claim 6, wherein the part of the
embedded one of the first and second heat sinks together with the
resin mold is removed in the step of removing by a cutting method
or a grinding method.
8. The method according to claim 7, wherein the part of the
embedded one of the first and second heat sinks together with the
resin mold is removed so that a first heat radiation surface of the
first heat sink and a second heat radiation surface of the second
heat sink have a degree of parallelism between the first and second
heat radiation surfaces equal to or smaller than 0.2 mm, and
wherein the first and second heat radiation surfaces are exposed
from the resin mold.
9. The method according to claim 8, wherein the degree of
parallelism is equal to or smaller than 0.15 mm.
10. The method according to claim 9, wherein the degree of
parallelism is equal to or smaller than 0.1 mm.
11. The method according to claim 6, wherein the step of molding
the heater element includes a step of forming a first surface and a
second surface of the resin mold, wherein the first surface of the
resin mold covers the one of the first and second heat sinks so
that the one of the first and second heat sinks is embedded,
wherein the second surface of the resin mold does not cover the one
of the first and second heat sinks, wherein the first surface of
the resin mold is protruded from the second surface of the resin
mold to have a step between the first and second surfaces of the
resin mold, and wherein the part of the embedded one of the first
and second heat sinks together with the resin mold is removed only
from the first surface of the resin mold so that the embedded one
of the first and second heat sinks is exposed from the resin
mold.
12. A method for manufacturing a semiconductor device, the method
comprising the steps of: sandwiching both sides of a heater element
by first and second heat sinks so that the heat sinks and the
heater element are thermally connected; molding the heater element
together with the first and second heat sinks with a resin mold in
such a manner that at least one of the first and second heat sinks
is embedded in the resin mold; removing a part of the resin mold
disposed on the embedded one of the first and second heat sinks so
that the embedded one of the first and second heat sinks is exposed
from the resin mold; and refreshing a surface of the exposed one of
the first and second heat sinks.
13. The method according to claim 12, wherein the step of
refreshing is performed by cutting the surface of the exposed one
of the first and second heat sinks.
14. The method according to claim 12, wherein the step of
refreshing is performed by grinding the surface of the exposed one
of the first and second heat sinks.
15. The method according to claim 12, wherein the surface of the
exposed one of the first and second heat sinks is refreshed in the
step of refreshing so that a first heat radiation surface of the
first heat sink and a second heat radiation surface of the second
heat sink have a degree of parallelism between the first and second
heat radiation surfaces equal to or smaller than 0.2 mm, and
wherein the first and second heat radiation surfaces are exposed
from the resin mold.
16. The method according to claim 15, wherein the degree of
parallelism is equal to or smaller than 0.15 mm.
17. The method according to claim 16, wherein the degree of
parallelism equal to or smaller than 0.1 mm.
18. The method according to claim 12, wherein the step of molding
the heater element includes a step of forming a first surface and a
second surface of the resin mold, wherein the first surface of the
resin mold covers the one of the first and second heat sinks so
that the one of the first and second heat sinks is embedded,
wherein the second surface of the resin mold does not cover the one
of the first and second heat sinks, wherein the first surface of
the resin mold is protruded from the second surface of the resin
mold to have a step between the first and second surfaces of the
resin mold, and wherein the part of the resin mold disposed on the
embedded one of the first and second heat sinks is removed only
from the first surface of the resin mold so that the embedded one
of the first and second heat sinks is exposed from the resin
mold.
19. The method according to claim 12, wherein the part of the resin
mold disposed on the embedded one of the first and second heat
sinks is removed by a laser beam cutting method, a water jet
cutting method or a shot blast cutting method.
20. The method according to claim 19, wherein the laser beam
cutting method is performed by a CO.sub.2 laser or a YAG laser.
21. The method according to claim 19, wherein the water jet cutting
method is performed by a water jet.
22. The method according to claim 19, wherein the shot blast
cutting method is performed by a sandblast.
23. The method according to claim 12, wherein the part of the resin
mold disposed on the embedded one of the first and second heat
sinks is removed by a releasing agent, the method further includes
the steps of: applying the releasing agent on the one of the first
and second heat sinks before the step of molding the heater element
together with the first and second heat sinks, wherein the part of
the resin mold disposed on the embedded one of the first and second
heat sinks through the releasing agent is removed at an interface
between the part of the resin mold and the embedded one of the
first and second heat sinks.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on Japanese Patent Applications
No. 2003-324585 filed on Sep. 17, 2003, and No. 2004-148933 filed
on May 19, 2004, the disclosures of which are incorporated herein
by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a semiconductor device
having a pair of heat sinks and a method for manufacturing the
same.
BACKGROUND OF THE INVENTION
[0003] A semiconductor device includes a heater element and a pair
of heat sinks disposed on both sides of the heater element. The
heater element and the heat sinks are sealed with resin, i.e., they
are molded with a resin mold. A heat radiation surface of each heat
sink is exposed from the resin mold.
[0004] The heat sinks are composed of the first heat sink and the
second heat sink. The first heat sink is disposed on one side of
the heater element, and thermally connects to the heater element.
The second heat sink is disposed on the other side of the heater
element, and thermally connects to the heater element. This
construction is defined as a both sides heat sink construction.
[0005] The semiconductor device having the both sides heat sink
construction is disclosed in Japanese Patent Application
Publications No. 2001-267469 and No. 2002-110893 (which corresponds
to U.S. Pat. No. 6,693,350). The device is manufactured by a
transfer mold method as follows. A pair of heat sinks is mounted on
both sides of the heater element, and the heater element with the
heat sinks is mounted in a mold, i.e., a die. Then, resin is molded
into the die so that the device is formed.
[0006] In the both sides heat sink construction, heat generated in
the heater element is radiated from both sides of the heater
element through the heat sinks, so that heat radiation
characteristic of the device is improved. Here, the heat sinks have
heat radiation surfaces, which are exposed from the resin mold.
However, an assembling error of the heat sinks or a slant of the
surface of the heat sinks may prevent the heat radiation surface
from exposing outside sufficiently. For example, the heat sink
disposed on the upper side of the heater element is tilted from the
surface of the device so that the heat radiation surface is not
sufficiently exposed from the resin mold. Specifically, the heat
radiation surface may be covered with the resin mold.
[0007] In view of the problem, in prior, the heat sink includes a
deformable portion, which is disposed outer periphery of the
device. When the heater element and the heat sinks are molded with
the resin mold by using a die, i.e., a mold, the deformable portion
is deformed so that the heat radiation surface is attached to the
mold. Thus, no clearance is formed between the heat radiation
surface and the mold so that the resin mold is prevented from
inserting into the clearance. Accordingly, the heat radiation
surface is sufficiently exposed from the resin mold. However, when
the heat sink is pressed and inserted into the mold, the pressure
is concentrated into the deformable portion of the heat sink so
that all of the surfaces of the heat sink are not pressurized
uniformly. Therefore, a portion of the heat sink, in which the
pressure is comparatively applied weakly, may be expanded or
deformed by the pressure of the resin mold inserted into the die.
This deformation of the heat sink causes to decrease the degree of
parallelism between the heat radiation surfaces of the heat sinks
so that the clearance may be formed between the heat radiation
surfaces and cooling equipment in a case where the device is
attached to the cooling equipment. Thus, cooling performance of the
device is reduced.
SUMMARY OF THE INVENTION
[0008] In view of the above-described problem, it is an object of
the present invention to provide a method for manufacturing a
semiconductor device having a both sides heat sink construction.
The heat radiation of the device is improved so that cooling
performance is improved. Further, it is another object of the
present invention to provide a semiconductor device having a both
sides heat sink construction and having excellent cooling
performance.
[0009] A semiconductor device includes a heater element; a first
heat sink disposed on one side of the heater element so that the
first heat sink thermally connects to the heater element; a second
heat sink disposed on the other side of the heater element so that
the second heat sink thermally connects to the heater element; and
a resin mold for molding the heater element and the first and
second heat sinks. The first heat sink includes a first heat
radiation surface, which is disposed opposite to the heater element
and exposed from the resin mold. The second heat sink includes a
second heat radiation surface, which is disposed opposite to the
heater element and exposed from the resin mold. The first and
second heat radiation surfaces have a degree of parallelism
therebetween equal to or smaller than 0.2 mm.
[0010] In the device, a thermal resistance in a heat radiation path
of the heater element is reduced by controlling the degree of
parallelism so that the heat radiation of the device is improved.
Thus, the cooling performance of the device is also improved.
[0011] Further, a method for manufacturing a semiconductor device
includes the steps of: sandwiching both sides of a heater element
by first and second heat sinks so that the heat sinks and the
heater element are thermally connected; molding the heater element
together with the first and second heat sinks with a resin mold in
such a manner that at least one of the first and second heat sinks
is embedded in the resin mold; and removing a part of the embedded
one of the first and second heat sinks together with the resin mold
so that the embedded one of the first and second heat sinks is
exposed from the resin mold.
[0012] The above method provides the semiconductor device. In the
device, both of the first and second heat radiation surfaces are
exposed from the resin mold so that the heat radiation of the
device is improved. Thus, the cooling performance of the device is
also improved.
[0013] Preferably, the part of the embedded one of the first and
second heat sinks together with the resin mold is removed in the
step of removing by a cutting method or a grinding method. More
preferably, the part of the embedded one of the first and second
heat sinks together with the resin mold is removed so that a first
heat radiation surface of the first heat sink and a second heat
radiation surface of the second heat sink have a degree of
parallelism between the first and second heat radiation surfaces
equal to or smaller than 0.2 mm. The first and second heat
radiation surfaces are exposed from the resin mold. In this case, a
thermal resistance in a heat radiation path of the heater element
is reduced by controlling the degree of parallelism so that the
heat radiation of the device is improved. Thus, the cooling
performance of the device is also improved.
[0014] Furthermore, a method for manufacturing a semiconductor
device includes the steps of: sandwiching both sides of a heater
element by first and second heat sinks so that the heat sinks and
the heater element are thermally connected; molding the heater
element together with the first and second heat sinks with a resin
mold in such a manner that at least one of the first and second
heat sinks is embedded in the resin mold; removing a part of the
resin mold disposed on the embedded one of the first and second
heat sinks so that the embedded one of the first and second heat
sinks is exposed from the resin mold; and refreshing a surface of
the exposed one of the first and second heat sinks.
[0015] The above method provides the semiconductor device. In the
device, both of the first and second heat radiation surfaces are
exposed from the resin mold so that the heat radiation of the
device is improved. Thus, the cooling performance of the device is
also improved.
[0016] Preferably, the step of refreshing is performed by cutting
the surface of the exposed one of the first and second heat sinks.
Preferably, the step of refreshing is performed by grinding the
surface of the exposed one of the first and second heat sinks.
Preferably, the surface of the exposed one of the first and second
heat sinks is refreshed in the step of refreshing so that a first
heat radiation surface of the first heat sink and a second heat
radiation surface of the second heat sink have a degree of
parallelism between the first and second heat radiation surfaces
equal to or smaller than 0.2 mm. The first and second heat
radiation surfaces are exposed from the resin mold. In this case, a
thermal resistance in a heat radiation path of the heater element
is reduced by controlling the degree of parallelism so that the
heat radiation of the device is improved. Thus, the cooling
performance of the device is also improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The above and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description made with reference to the accompanying
drawings. In the drawings:
[0018] FIG. 1 is a cross sectional view showing a semiconductor
device according to a first embodiment of the present
invention;
[0019] FIG. 2 is a cross sectional view explaining a method for
manufacturing the device, according to the first embodiment;
[0020] FIG. 3 is a cross sectional view showing semiconductor
equipment including the device according to the first
embodiment;
[0021] FIG. 4 is a graph showing a relationship between a thermal
resistance and a degree of parallelism in the device according to
the first embodiment;
[0022] FIG. 5 is a cross sectional view showing a semiconductor
device according to a modification of the first embodiment;
[0023] FIG. 6 is a cross sectional view explaining a method for
manufacturing a semiconductor device according to a second
embodiment of the present invention;
[0024] FIG. 7 is a cross sectional view showing semiconductor
equipment according to a third embodiment of the present
invention;
[0025] FIG. 8 is a cross sectional view showing semiconductor
equipment according to a fourth embodiment of the present
invention;
[0026] FIGS. 9A and 9B are schematic views explaining a method for
cutting and grinding a resin mold, according to a fifth embodiment
of the present invention;
[0027] FIG. 10 is a schematic view explaining a method for removing
a resin mold by a laser beam, according to a sixth embodiment of
the present invention;
[0028] FIG. 11 is a schematic view explaining a method for removing
the resin mold by a water jet method, according to the sixth
embodiment;
[0029] FIG. 12 is a schematic view explaining a method for removing
the resin mold by a shot blast method, according to the sixth
embodiment;
[0030] FIG. 13 is a schematic view explaining a method for removing
the resin mold by a releasing agent, according to the sixth
embodiment; and
[0031] FIG. 14 is a cross sectional view showing a semiconductor
device as a comparison, according to the first embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0032] The inventors have preliminarily studied about a
semiconductor device having a both sides heat sink construction.
FIG. 14 shows a semiconductor device 500 having a heater element 10
and the first and second heat sinks 30, 40. The first and second
heat sinks 30, 40 are thermally connected to the heater element 10
through a connecting member 50 and an electrode block 20. The
heater element 10 is electrically connected to a lead terminal 60
through a bonding wire 70. The heater element 10, the first and
second heat sinks 30, 40, their connecting portions, the bonding
wire 70, and a part of the lead terminal 60 are sealed, i.e.,
molded with a resin mold 80.
[0033] Here, the first heat sink 30 has the first heat radiation
surface 30a, and the second heat sink 40 has the second heat
radiation surface 40a. The first and second heat radiation surfaces
30a, 40a are exposed from the resin mold 80. However, an assembling
error of the heat sinks 30, 40 or a slant of the heat radiation
surfaces of the heat sinks 30, 40 may prevent the heat radiation
surfaces 30a, 40a from exposing outside sufficiently. For example,
in FIG. 14, the first heat sink 30 disposed on the upper side of
the heater element 10 is tilted from the surface of the device 500
so that the first heat radiation surface 30a is not sufficiently
exposed from the resin mold 80. A part of the first heat radiation
surface 30a is covered with the resin mold 80.
[0034] The above problem is caused by a deviation of a distance
between the heat radiation surfaces 30a, 40a of heat sinks 30, 40,
a deviation of thicknesses of the heat sinks 30, 40, a deviation of
a thickness of the heater element 10, and/or an assembling error
for assembling the heat sinks 30, 40. Because of these deviations,
a clearance is formed between the heat radiation surfaces 30a, 40a
of the heat sinks 30, 40 and the die when the parts are molded with
resin by using the die. The resin is inserted into the clearance so
that the heat radiation surfaces 30a, 40a may be covered with the
resin mold 80. Further, if the heat radiation surface 30a, 40a is
tilted from the surface of the device 500, another clearance is
formed between the heat radiation surface 30a, 40a and cooling
equipment (not shown) in a case where the device 500 is attached to
the cooling equipment for improving cooling performance. Thus, the
device 500 is not cooled by the cooling equipment sufficiently.
[0035] In view of the above problem, a semiconductor device 100
according to a first embodiment of the present invention is shown
in FIG. 1. The device 100 includes a heater element 10 such as a
heat generation semiconductor chip. The heater element 100 is, for
example, a transistor such as an IGBT (integrated gate bipolar
transistor) or a FWD (free wheel diode), which generates heat when
the transistor works.
[0036] The first heat sink 30 is disposed on one side of the heater
element 10 through an electrode block 20. The second heat sink 40
is disposed on the other side of the heater element 10. A
connecting member 50 is disposed between the heater element 10 and
the electrode block 20, between the electrode block 20 and the
first heat sink 30, and between the heater element 10 and the
second heat sink 40, respectively. The electrode block 20 is made
of excellent heat conductive material such as copper (i.e., Cu),
aluminum (i.e., Al), tungsten (i.e., W), molybdenum (i.e., Mo) or
the like. In this embodiment, the electrode block 20 is made of
copper plate, which is a little smaller than the heater element
10.
[0037] The first and second heat sinks 30, 40 are made of excellent
heat conductive material such as copper (i.e., Cu), aluminum (i.e.,
Al), tungsten (i.e., W), molybdenum (i.e., Mo) or the like. In this
embodiment, the first and second heat sinks 30, 40 are made of
copper plate, which is a little bigger than the heater element 10.
The connecting member 50 electrically and thermally connects
between the heater element 10 and the electrode block 20, between
the electrode block 20 and the first heat sink 30, and between the
heater element 10 and the second heat sink 40, respectively. The
connecting member 50 is made of, for example, a solder or a
conductive adhesive. Here, the conductive adhesive is formed such
that metallic filler is dispersed into resin. Thus, the first heat
sink 30 is thermally connected to the heater element 10 through the
connecting member 50 and the electrode block 20. The second heat
sink 40 is thermally connected to the heater element 10 through the
connecting member 50.
[0038] A lead terminal 60 is disposed on one side of the device
100. Specifically, the lead terminal 60 is disposed near the heater
element 10. The lead terminal 60 is made of conductive metallic
material such as copper. The heater element 10 and the lead
terminal 60 are connected with a bonding wire 70. The bonding wire
70 is made of aluminum, gold or the like. Thus, a signal terminal
(not shown) of the heater element 10 is electrically connected to
the lead terminal 60 through the bonding wire 70. The signal
terminal is, for example, a gate terminal of the IGBT. The heater
element 10, the electrode block 20, the first heat sink 30, the
second heat sink 40, the bonding wire 70, a part of the lead
terminal 60, and a connecting portion between the bonding wire 70
and the lead terminal 60 are sealed, i.e., molded with a resin mold
80. The resin mold 80 is made of a conventional resin mold such as
epoxy resin. The conventional resin mold is used for a mold package
of a semiconductor device. The first and second heat sinks 30, 40
include the upper and lower heat radiation surfaces (i.e., the
first and second heat radiation surfaces) 30a, 40a, respectively.
Specifically, the upper heat radiation surface 30a of the first
heat sink 30 is disposed on one surface of the first heat sink 30,
which is opposite to the heater element 10. The lower heat
radiation surface 40a of the second heat sink 40 is disposed on one
surface of the second heat sink 40, which is opposite to the heater
element 10. The upper and lower heat radiation surfaces 30a, 40a of
the first and second heat sinks 30, 40 are exposed from the resin
mold 80. The degree of parallelism between the first heat radiation
surface 30a of the first heat sink 30 and the second heat radiation
surface 40a of the second heat sink 40 is equal to or lower than
0.2 mm. The degree of parallelism is defined in JIS (i.e., Japanese
Industrial Standard). Specifically, the parallelism is defined in
No. B-0621, JIS hand book. Preferably, the degree of parallelism is
equal to or smaller than 0.15 mm. More preferably, the degree of
parallelism is equal to or smaller than 0.1 mm.
[0039] The semiconductor device 100 is manufactured as flows.
Firstly, the heater element 10 is mounted and bonded on the second
heat sink 40 through the connecting member 50. Then, the electrode
block 20 is bonded on the heater element 10 through the connecting
member 50. However, the electrode block 20, the connecting member
50, the heater element 10, the connecting member 50 and the second
heat sink 40 can be bonded at the same time.
[0040] Next, the lead terminal 60 is mounted next to the heater
element 10. The heater element 10 is bonded to the lead terminal 60
by the wire bonding method so that the bonding wire 70 is formed.
Thus, the signal terminal of the heater element 10 such as the gate
terminal of the IGBT and the lead terminal 60 are electrically
connected with the bonding wire 70. Then, the first heat sink 30 is
mounted on the electrode block 20 through the connecting member 50.
The heater element 10, the electrode block 20, the first heat sink
30, the second heat sink 40, the bonding wire 70 and the lead
terminal 60 are integrated so that the above integrated parts
(i.e., works) are formed. The integrated parts are mounted in the
die, i.e., the mold so that the integrated parts are molded with
resin by the transfer mold method. Thus, the integrated parts are
molded and covered with the resin mold 80.
[0041] In the above transfer mold process, at least one of the
first heat radiation surface 30a of the first heat sink 30 and the
second heat radiation surface 40a of the second heat sink 40 is
embedded in the resin mold 80, as shown in FIG. 2. In the first
embodiment, the first heat radiation surface 30a of the first heat
sink 30 disposed on the upper side of the heater element 10 is
embedded in the resin mold 80. This construction is easily obtained
by forming a clearance between the first heat radiation surface 30a
and the die (i.e., an upper portion of the die). The second heat
sink 40, which is disposed under the heater element 10, is pressed
and attached to the die (i.e., a lower portion of the die), so that
the second heat radiation surface 40a is exposed from the resin
mold 80. The degree of parallelism between the first and second
heat radiation surfaces 30a, 40a of the heat sinks 30, 40 may be
equal to or smaller than 0.2 mm. However, the degree of parallelism
can be larger than 0.2 mm. In FIG. 2, the degree of parallelism is
larger than 0.2 mm, so that the first heat radiation surface 30a of
the first heat sink 30 is tilted from the second heat radiation
surface 40a of the second heat sink 40.
[0042] Next, the molded parts, i.e., the integrated parts are
retrieved from the die. Then, the first heat radiation surface 30a
of the first heat sink 30, which is embedded in the resin mold 80,
is polished, ground or cut together with the resin mold 80 from the
outside of the resin mold 80 so that the first heat radiation
surface 30a is exposed from the resin mold 80. Specifically, the
first heat sink 30 with the resin mold 80 is ground by a grinder or
cut by a cutter to a level K shown as a broken line in FIG. 2 from
the upside of the resin mold 80. Thus, the first heat radiation
surface 30a is exposed from the resin mold 80 at the level K. The
exposed first heat radiation surface 30a is formed by grinding or
cutting a part of the first heat sink 30 with the resin mold 80.
The exposed (i.e., ground or cut) first heat radiation surface 30a
becomes the new first heat radiation surface 30a of the first heat
sink 30 in the device 100 shown in FIG. 1.
[0043] In the grinding or cutting process, the degree of
parallelism between the first and second heat radiation surfaces
30a, 40a becomes to be equal to or smaller than 0.2 mm. Preferably,
the degree of parallelism is equal to or smaller than 0.15 mm. More
preferably, the degree of parallelism is equal to or smaller than
0.1 mm. Thus, the semiconductor device 100 is completed.
[0044] Although the first heat radiation surface 30a is embedded in
the resin mold 80, the second heat radiation surface 40a instead of
the first heat radiation surface 30a can be embedded in the resin
mold 80. In this case, the second heat sink 40 with the resin mold
80 is ground or cut so that the second heat radiation surface 40a
is exposed from the resin mold 80. Further, both of the first and
second heat radiation surfaces 30a, 40a of the first and second
heat sinks 30, 40 can be embedded in the resin mold 80. In this
case, both of the first and second heat sinks 30, 40 with the resin
mold 80 are ground or cut so that both of the first and second heat
radiation surfaces 30a, 40a are exposed from the resin mold 80.
[0045] In the device 100, since the first and second heat radiation
surfaces 30a, 40a are exposed from the resin mold 80, and the
degree of parallelism between the first and second heat radiation
surfaces 30a, 40a is equal to or smaller than 0.2 mm, thermal
resistance in a heat radiation path of the heater element 10
becomes smaller. This reduction effect of the thermal resistance
has been experimentally studied by the inventors. The experimental
results of the reduction effect are described as follows. FIG. 3
shows semiconductor equipment 200 including the semiconductor
device 100. The equipment 200 further includes a pair of cooling
blocks 110 as a cooling member disposed outside of the heat
radiation surfaces 30a, 40a of the heat sinks 30, 40, respectively.
The cooling block 110 as cooling equipment cools the heat sink 30,
40 from the heat radiation surface 30a, 40a.
[0046] Specifically, the cooling block 110 is disposed on the heat
radiation surface 30a, 40a through an insulation member 120 so that
the cooling block 110 and the heat sink 30, 40 are thermally
connected. The insulation member 120 has electrical insulating
property and has a thermal conductivity. The cooling block 110
includes a coolant path 110a, in which coolant such as cooling
water flows. The heat generated in the heater element 10 and
conducted through the heat sinks 30, 40 is cooled by the cooling
water in the coolant path 110a. Thus, the heat is exchanged between
the cooling water and the heater element 10 so that the heater
element is cooled.
[0047] Thus, the heat radiation (i.e., cooling performance) of the
device 100 is much improved by the equipment 200. The insulation
member 120 is made of, for example, electrical insulation plate
such as aluminum nitride (i.e., AlN). Further, heat conductive
grease having electrical insulation can be applied between the
insulation plate 120 and the cooling block 110 or between the
insulation plate 120 and the heat sink 30, 40.
[0048] The reduction effect of the thermal resistance is tested as
follows. The equipment 200 is mounted on a base 900 so that load G
is applied to the equipment 200 from the upper side of the
equipment 200, i.e., from the upper cooling block 110. The load G
is, for example, 0 to 1500 kGf. The heater element 10 generates
heat by driving (i.e., working) the heater element 10. In FIG. 3,
the heat of the heater element 10 is 65 W. The insulation plate 120
is made of aluminum nitride, and has a plate shape. The cooling
water flowing through the coolant path 110a has a flow rate of 6
liters per minute (i.e., L/min). The temperature of the cooling
water is 40.degree. C. The area of each heat radiation surface 30a,
40a is 30 mm by 15 mm (i.e., 30 mm.times.15 mm). The degree of
flatness of each surface 30a, 40a is about 50 .mu.m. The degree of
flatness is defined in JIS (i.e., Japanese Industrial Standard).
Specifically, the flatness is defined in No. B-0621, JIS hand book.
Here, the degree of parallelism H shown in FIG. 3 between the
surfaces 30a, 40a is determined by a reference surface as the
second heat radiation surface 40a of the second heat sink 40. The
degree of parallelism H has unit of .mu.m.
[0049] The thermal resistance is determined in a heat radiation
path from the heater element 10 to the coolant path 110a in the
cooling block 110 through the heat sinks 230, 40 and the insulation
plate 120. Specifically, the temperature of the heater element 10
is defined as TC, the temperature of the cooling water is defined
as TW, and the heating value (i.e., heating power) of the heater
element 10 is defined as Q. Thus, the thermal resistance is shown
as (TC-TW)/Q, which has unit of K/W, i.e., Kelvin per watt.
[0050] The relationship between the degree of parallelism H and the
thermal resistance is studied in a case where the load G is applied
to the equipment 200. FIG. 4 shows a result of the relationship. In
FIG. 4, X represents the relationship when the load G is 50 kgf, Y
represents the relationship when the load G is 300 kgf, and Z
represents when the load G is 1000 kgf. When the degree of
parallelism H is equal to or smaller than 0.2 mm (i.e., 200 .mu.m),
the thermal resistance is almost constant and comparatively low.
When the degree of parallelism H exceeds over 0.2 mm, the thermal
resistance increases. To reduce the thermal resistance, it is
preferred that the degree of parallelism is equal to or smaller
than 0.15 mm. More preferably, the degree of parallelism is equal
to or smaller than 0.1 mm.
[0051] When the load G becomes larger, the thermal resistance
generally becomes smaller. This is because the thickness of the
equipment 200 becomes thinner when the load G becomes larger. Thus,
the heat radiation path becomes shorter, and further, adhesion at
an interface between parts in the heat radiation path becomes
tightened so that the thermal resistance becomes smaller.
[0052] Thus, the thermal resistance in the heat radiation path of
the heater element 10 is reduced by controlling the degree of
parallelism so that the heat radiation of the equipment 200, i.e.,
the device 100 is improved. Thus, the cooling performance of the
device 100 is improved.
[0053] Further, in the equipment 200, the cooling block 110
disposed outside of the heat radiation surfaces 30a, 40a much
improves the heat radiation of the heater element 10. In FIG. 3,
the load G is applied to the heat sinks 30, 40 and the heater
element 10 through the upper and lower cooling blocks 110. The load
G can be applied to the cooling blocks 110 by a spring or the
like.
[0054] In the above method for manufacturing the device 100, the
degree of parallelism H can be controlled appropriately by cutting
or grinding the heat radiation surfaces 30a, 40a. This is, a tilt
angle of the heat radiation surfaces 30a, 40a can be controlled to
a predetermined angle so that the degree of parallelism H is set to
be a predetermined value.
[0055] Although the device 100 includes one heater element 10, the
device 100 can include multiple heater elements 10, as shown in
FIG. 5. In FIG. 5, two heater elements 10, 11 are disposed between
the first and second heat sinks 30, 40. For example, one of the
heater elements 10, 11 is the IGBT, and the other heater element
10, 11 is the FWD. The integrated parts, which is composed of the
heater element 10, the electrode block 20, the first heat sink 30,
and the second heat sink 40, are mounted in a die 910, i.e., a mold
so that the integrated parts are molded with resin. In this case,
the first heat radiation surface 30a of the first heat sink 30 is
embedded in the resin mold 80. The die 910 includes an upper die
911 and a lower die 912. The upper die 911 works as a holding
member for holding the second heat sink 40 disposed under the
heater elements 10, 11 so that the second heat sink 40 is pressed
and attached to the lower die 912. Therefore, no resin penetrates
on the second heat radiation surface 40a of the second heat sink 40
so that the second heat radiation surface 40a is exposed from the
resin mold 80 sufficiently. The first heat sink 30 with the resin
mold 80 is cut or ground so that the first heat radiation surface
30a is exposed from the resin mold 80. Thus, multiple heater
elements 10, 11 are sandwiched by the heat sinks 30, 40.
[0056] In the prior art, when multiple heater elements are
sandwiched by the heat sinks, the resin mold for molding the heater
elements is expanded so that the heat sinks are deformed. This
deformation, i.e., expansion of the heat sinks may deteriorate the
degree of parallelism between the heat radiation surfaces of the
heat sinks so that a clearance is formed between the cooling
equipment and the heat radiation surfaces.
[0057] However, in this method according to the first embodiment,
even when the heat sink is deformed or expanded, the expanded
portion of the heat sink is cut or ground so that the degree of
parallelism is improved. Specifically, the expanded portion of the
heat sink can be cut or ground so that a flat surface of the heat
sink is obtained.
Second Embodiment
[0058] A method for manufacturing the device 100 according to a
second embodiment of the present invention is shown in FIG. 6. In
FIG. 6, the integrated parts are molded with the resin mold 80 in
the resin molding process, i.e., the transfer molding process. The
resin mold 80 has the first upper surface 80a and second upper
surface 80b. The first upper surface 80a covers the first heat
radiation surface 30a of the first heat sink 30 so that the first
heat radiation surface 30a is embedded in the resin mold 80. The
second upper surface 80b does not cover the first heat radiation
surface 30a. The first upper surface 80a of the resin mold 80 and
the first heat radiation surface 30a of the first heat sink 30 are
protruded from the second upper surface 80b of the resin mold 80 so
that the first upper surface 80a has a step from the second upper
surface 80b. Thus, the resin molding process provides the resin
mold 80 having the first and second upper surfaces 80a, 80b.
[0059] Here, the first upper surface 80a of the resin mold 80 works
as a protruded upper surface 80a, and the second upper surface 80b
works as a base upper surface 80b (i.e., a step upper surface). In
the grinding or cutting process, the protruded portion, i.e., the
protruded upper surface 80a with the first heat radiation surface
30a is cut or ground to the level K. Thus, the grinding or cutting
process is ended before the grinder or the cutter reaches the step
upper surface 80b. Thus, the protruded portion is removed so that
the first heat radiation surface 30a of the first heat sink 30 is
exposed from the resin mold 80. Accordingly, only the protruded
portion is removed; and therefore, the grinding or cutting portion
becomes smaller, and the grinding or cutting time, i.e., the
process time is reduced.
[0060] Thus, the thermal resistance in the heat radiation path of
the heater element 10 is reduced by controlling the degree of
parallelism so that the heat radiation of the device 100 is
improved. Accordingly, the cooling performance of the device 100 is
improved.
Third Embodiment
[0061] Semiconductor equipment 300 according to a third embodiment
of the present invention is shown in FIG. 7. The equipment 300
includes multiple semiconductor devices 100, which are disposed
vertically. The cooling block 110 is disposed between the devices
100 so that multiple devices 100 and multiple cooling blocks 110
are laminated.
[0062] In the equipment 300, the cooling block 110 is disposed
outside of the heat radiation surface 30a, 40a of the heat sink 30,
40 through the insulation member 120 (not shown) so that the heat
sink 30, 40 and the cooling block 110 are thermally connected. The
load is applied to the equipment 300 in a lamination direction,
i.e., a vertical direction so that the cooling performance of the
equipment 300 is improved. The load can be applied by a spring or
the like disposed outside of the cooling block 110.
[0063] Thus, the thermal resistance in the heat radiation path of
the heater element 10 is reduced by controlling the degree of
parallelism so that the heat radiation of the device 100, i.e., the
equipment 300 is improved.
Fourth Embodiment
[0064] Semiconductor equipment 400 according to a fourth embodiment
of the present invention is shown in FIG. 8. The equipment 400
includes multiple semiconductor devices 100, which are disposed
horizontally. Thus, multiple devices 100 are sandwiched by a pair
of cooling blocks 110. The devices 100 are disposed on the same
plane.
[0065] In the equipment 400, the cooling block 110 is disposed
outside of the heat radiation surface 30a, 40a of the heat sink 30,
40 through the insulation member 120 (not shown) so that the heat
sink 30, 40 and the cooling block 110 are thermally connected.
Thus, the upper and lower cooling blocks 100 sandwich multiple
devices 100. The load is applied to the devices 100 through a pair
of cooling blocks 110 by a spring or the like.
[0066] Thus, the thermal resistance in the heat radiation path of
the heater element 10 is reduced by controlling the degree of
parallelism so that the heat radiation of the device 100, i.e., the
equipment 400 is improved.
[0067] Further, multiple devices 100 disposed in parallel are
sandwiched by a pair of cooling blocks 110. In this case, if the
height, i.e., the thickness of each device 100 is different, the
cooling block 110 does not sufficiently contact the heat radiation
surfaces 30a, 40a. This is, for example, in a case where one of the
device 100 is thinner than the other device 100, i.e., the height
of the one device 100 is lower than the other device 100, a
clearance is formed between the heat radiation surface of the one
device 100 and the cooling block 110 so that the heat radiation of
the one device 100 is decreased. However, the height, i.e., the
thickness of each device 100 can be controlled by cutting or
grinding the heat sink 30, 40 with the resin mold 80 in the
grinding or cutting process. Thus, the height of one device 100 is
easily equalized to the other device 100. Accordingly, no clearance
is formed between the devices 100 and the cooling block 110 so that
the cooling performance of the device 100 is improved.
Fifth Embodiment
[0068] In the cutting or grinding process, the heat sink 30, 40
with the resin mold 80 is cut or ground by a cutter or a grinder so
that the heat radiation surface 30a, 40a is exposed from the resin
mold 80. A method for cutting or grinding according to a fifth
embodiment is shown in FIGS. 9A and 9B. In FIG. 9A, the portion of
the heat sink 30 with the resin mold 80, which has a predetermined
thickness, is removed at one time by a cutter K1. In FIG. 9B, the
portion of the heat sink 30 with the resin mold 80 is removed
gradually by a grinder K2. For example, the portion is ground step
by step, that is a few microns per one step. Thus, the device 100
is completed. The device 100 has a excellent cooling
performance.
Six Embodiment
[0069] A method for manufacturing the device 100 according to a
sixth embodiment is such that the heat radiation surface 30a, 40a
is cut or ground after a part of the resin mold 80, which covers
the heat radiation surface 30a, 40a of the heat sink 30, 40, is
removed.
[0070] The method is shown in FIG. 10 and described as follows.
Firstly, in the resin molding process, at least one of the first
heat radiation surface 30a of the first heat sink 30 and the second
heat radiation surface 40a of the second heat sink 40 is embedded
in the resin mold 80. In the sixth embodiment, the first heat
radiation surface 30a of the first heat sink 30 disposed on the
upper side of the heater element 10 is embedded in the resin mold
80. Then, the resin mold 80 is removed so that the heat radiation
surface 30a of the first heat sink 30 is exposed from the resin
mold 80. The resin mold 80 is removed by a laser beam, water jet,
or a shot blast.
[0071] In FIG. 10, the resin mold 80 is removed by a laser beam K4
emitted from laser equipment K3. The laser equipment K3 is, for
example, a CO.sub.2 laser equipment (i.e., carbon dioxide gas laser
equipment), or YAG laser equipment (i.e., yttrium aluminum garnet
laser equipment). Next, the exposed first heat radiation surface
30a of the heat sink 30 is ground by the grinder or cut by the
cutter. In this case, since the heat radiation surface 30a is cut
or ground after the part of the resin mold 80, which covers the
heat radiation surface 30a, is removed, the tilt angle of the heat
radiation surface 30a can be controlled appropriately. Thus, the
degree of parallelism between the heat radiation surfaces 30a, 40a
is controlled to be a predetermined value. Thus, the thermal
resistance in the heat radiation path of the heater element 10 is
reduced by controlling the degree of parallelism so that the heat
radiation of the device 100 is improved.
[0072] Although the part of the resin mold 80 is removed by the
laser beam K4, the part of the resin mold 80 can be removed by a
water jet, a shot blast, or a releasing agent. In FIG. 11, the part
of the resin mold 80 is removed by a water jet processing method.
The water jet K6 is jetted from a nozzle K5 so that the part of the
resin mold 80 is removed. In FIG. 12, the part of the resin mold 80
is removed by a shot blast (i.e., sandblast) processing method. The
sandblast K8 is jetted from a nozzle K7 so that the part of the
resin mold 80 is removed. In FIG. 13, the part of the resin mold 80
is removed by the releasing agent K9. The releasing agent K9 is a
kind of oil, and used for a resin foaming method in general.
Specifically, the releasing agent K9 is applied to the heat
radiation surface 30a. Then, the resin molding process is performed
so that the heat radiation surface 30a is covered with the resin
mold 80 through the releasing agent K9. Accordingly, the heat
radiation surface 30a is easily separated from the resin mold 80
because the releasing agent K9 is disposed at the interface between
the resin mold 80 and the heat radiation surface 30a. Thus, the
heat radiation surface 30a is exposed from the resin mold 80.
[0073] Such changes and modifications are to be understood as being
within the scope of the present invention as defined by the
appended claims.
* * * * *