U.S. patent application number 10/242862 was filed with the patent office on 2003-02-13 for laminated radiation member, power semiconductor apparatus, and method for producing the same.
This patent application is currently assigned to NGK Insulators, Ltd.. Invention is credited to Araki, Kiyoshi, Bessyo, Yuki, Ishikawa, Takahiro, Kida, Masahiro, Makino, Takuma.
Application Number | 20030030141 10/242862 |
Document ID | / |
Family ID | 18549583 |
Filed Date | 2003-02-13 |
United States Patent
Application |
20030030141 |
Kind Code |
A1 |
Araki, Kiyoshi ; et
al. |
February 13, 2003 |
Laminated radiation member, power semiconductor apparatus, and
method for producing the same
Abstract
A laminated radiation member includes a radiation plate, an
insulation substrate bonded to the upper surface of the radiation
plate and an electrode provided on the upper surface of the
insulation substrate. The laminated radiation member is made by a
method including the steps of surface treating a bonding surface of
the radiation plate and/or the insulation substrate, interposing
ceramic particles surface treated to assure wettability with a hard
solder or a metal between the radiation plate and the insulation
substrate, disposing a hard solder above and/or below the ceramic
particles, heating the hard solder to a temperature higher than the
melting point of the solder, penetrating the molten hard solder
into spaces between the ceramic particles to react the ceramic
particles with the solder to produce a metal base composite
material, and bonding the radiation plate and the insulation
substrate with the metal base composite material.
Inventors: |
Araki, Kiyoshi; (Ann Arbor,
MI) ; Kida, Masahiro; (Nagoya-city, JP) ;
Ishikawa, Takahiro; (Nagoya-city, JP) ; Bessyo,
Yuki; (Nishikasugai-gun, JP) ; Makino, Takuma;
(Kasugai-city, JP) |
Correspondence
Address: |
BURR & BROWN
PO BOX 7068
SYRACUSE
NY
13261-7068
US
|
Assignee: |
NGK Insulators, Ltd.
|
Family ID: |
18549583 |
Appl. No.: |
10/242862 |
Filed: |
September 13, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10242862 |
Sep 13, 2002 |
|
|
|
09774206 |
Jan 30, 2001 |
|
|
|
Current U.S.
Class: |
257/720 ;
257/703; 257/E23.098; 257/E23.106 |
Current CPC
Class: |
C04B 2237/72 20130101;
C23C 24/10 20130101; C04B 2237/121 20130101; C04B 2237/064
20130101; H01L 2924/01013 20130101; H01L 2924/01012 20130101; H01L
2924/13055 20130101; C04B 2237/122 20130101; H01L 24/45 20130101;
C04B 2237/368 20130101; H01L 23/3735 20130101; C04B 2235/6565
20130101; H01L 2924/01072 20130101; C04B 2235/9607 20130101; H01L
2224/73265 20130101; C04B 2237/704 20130101; C23C 4/08 20130101;
H01L 2924/01078 20130101; H01L 2924/0133 20130101; H01L 2924/01006
20130101; H01L 2924/01041 20130101; C04B 2235/3206 20130101; C23C
6/00 20130101; H01L 2224/2612 20130101; H01L 2924/0105 20130101;
H01L 2924/01074 20130101; C04B 2237/125 20130101; H01L 23/473
20130101; C04B 2237/706 20130101; H01L 24/32 20130101; C04B 2237/56
20130101; H01L 2924/01327 20130101; H01L 2924/01075 20130101; C23C
24/106 20130101; H01L 2924/0132 20130101; H01L 2924/15787 20130101;
C23C 4/02 20130101; C04B 37/026 20130101; C04B 2235/3225 20130101;
C04B 2237/083 20130101; C04B 2237/127 20130101; H01L 23/3736
20130101; H01L 2224/451 20130101; H01L 2924/01005 20130101; H01L
2924/01033 20130101; Y10T 428/24926 20150115; C04B 2237/365
20130101; H01L 2924/01073 20130101; C04B 2237/128 20130101; H01L
24/48 20130101; Y10T 428/24917 20150115; H01L 2924/0104 20130101;
H01L 2224/45124 20130101; C04B 2237/366 20130101; C04B 2237/407
20130101; H01L 2924/01029 20130101; H01L 2924/01046 20130101; H01L
2924/19107 20130101; H01L 2224/48091 20130101; H01L 2924/01047
20130101; Y10T 428/252 20150115; C04B 2235/3873 20130101; C04B
2235/616 20130101; H01L 23/3733 20130101; H01L 2924/01042 20130101;
H01L 2924/351 20130101; H01L 2224/48091 20130101; H01L 2924/00014
20130101; H01L 2924/0132 20130101; H01L 2924/01004 20130101; H01L
2924/01029 20130101; H01L 2924/0132 20130101; H01L 2924/01022
20130101; H01L 2924/01029 20130101; H01L 2924/0133 20130101; H01L
2924/01022 20130101; H01L 2924/01029 20130101; H01L 2924/01047
20130101; H01L 2924/0132 20130101; H01L 2924/01029 20130101; H01L
2924/01042 20130101; H01L 2924/3512 20130101; H01L 2924/00
20130101; H01L 2924/13055 20130101; H01L 2924/00 20130101; H01L
2224/451 20130101; H01L 2924/00 20130101; H01L 2924/351 20130101;
H01L 2924/00 20130101; H01L 2924/15787 20130101; H01L 2924/00
20130101; H01L 2224/45124 20130101; H01L 2924/00015 20130101; H01L
2224/451 20130101; H01L 2924/00014 20130101 |
Class at
Publication: |
257/720 ;
257/703 |
International
Class: |
H01L 023/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2000 |
JP |
2000-023422 |
Claims
What is claimed is:
1. A power semiconductor apparatus comprising a circuit electrode,
a laminated radiation member comprising a radiation plate and an
insulation substrate, a semiconductor chip bonded to the circuit
electrode formed at the laminated radiation member and a metal wire
electrically connected to the semiconductor chip, said metal wire
electrically connected to the circuit electrode, said semiconductor
chip, said laminated radiation member and said circuit electrode
being sealed with an insulating sealer, said laminated radiation
member comprising a radiation plate, an insulation substrate bonded
to the upper surface of the radiation plate and an electrode
provided on the upper surface of the insulation substrate, wherein
said radiation plate and said insulation substrate are bonded with
a metal base composite material layer in which ceramic particles
are dispersed and which is present between the radiation plate and
the insulation substrate.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a laminated radiation
member, a power semiconductor apparatus, and a method for making
the same.
[0002] A known power semiconductor apparatus is, for example, one
which is composed of the main part as shown in FIG. 4. In FIG. 4,
101 indicates a power semiconductor apparatus, 102 indicates a
semiconductor chip comprising IGBT or the like, 103 indicates a
metal base plate for radiating the heat generated from the
semiconductor chip 102, 104 indicates a ceramic plate comprising
aluminum nitride or the like for insulating the semiconductor chip
102 from the metal base plate 103, 105a indicates a first metal
electrode provided above the upper surface of the ceramic plate
104, 105b indicates a second metal electrode provided below the
lower surface of the ceramic plate 104, 106a indicates a first hard
solder paste for bonding the ceramic plate 104 to the first metal
electrode 105a, 106b indicates a second hard solder paste for
bonding the ceramic plate 104 to the second metal electrode 105b,
107a indicates a first solder for bonding the semiconductor chip
102 to the first metal electrode 105a, 107b indicates a second
solder for bonding the metal base plate 103 to the first metal
electrode 105b, 108a indicates a first metal wire comprising
aluminum to be connected to the semiconductor chip 102, 108b
indicates a second metal wire comprising aluminum to be connected
to the first metal electrode 105a, and 109 indicates a silicone gel
which covers the semiconductor chip 102, the ceramic plate 104, the
first metal electrode 105a and the second metal electrode 105b and
seals them.
[0003] The conventional power semiconductor apparatus having the
above construction is usually made by the following method. In the
case of making the conventional power semiconductor apparatus 101,
first, hard solder pastes, which are the first and second hard
solder pastes 106a and 106b, are printed at a given thickness on
both surfaces of the ceramic plate 104. Then, two metal electrodes,
which are the first and second metal electrodes 105a and 105b, are
put on the hard solder pastes printed on both the surfaces of the
ceramic plate 104 and heat treated at a given temperature, for
example, about 850.degree. C., thereby bonding the first and second
metal electrodes to both surfaces of the ceramic plate 104.
[0004] Thereafter, the ceramic plate 104, to both surfaces of which
the metal electrodes are bonded is bonded, to the metal base plate
103 with a high-temperature solder (melting point: about
260.degree. C.) which is the second solder 107b, and the
semiconductor chip 102 is bonded with a low-temperature solder
(melting point: about 150.degree. C.), which is the first solder
107a, to both surfaces of the ceramic plate 104 on which the metal
electrodes are bonded. A metal wire, which is the first metal wire
108a, is connected to the semiconductor chip 102 by wire bonding,
and a metal wire, which is the second metal wire 108b, is connected
to the metal electrode which is the first metal electrode 105a by
wire bonding.
[0005] Usually, the metal base plate 103 on which the semiconductor
chip 102, the ceramic plate 104, the first metal electrode 105a and
the second metal electrode 105b, and the like are mounted is
contained in a package. Silicone gel 109 is vacuum injected into
the package and cured by heating, whereby the semiconductor chip
102, the ceramic plate 104, the first metal electrode 105a and the
second metal electrode 105b, and the like are covered with the
silicone gel 109 and sealed. In this way, the conventional power
semiconductor apparatus 101 is made.
[0006] However, since the insulation substrate (104) and the metal
electrodes (105a,b) are bonded with the hard solders (106a,b),
cracks occur due to the difference in expansion coefficient between
the insulation substrate, which has a low thermal expansion
coefficient, and the hard solders and metal electrodes, which have
high thermal expansion coefficients. Furthermore, since the
insulation substrate (104) and the radiation plate (103) are
connected with solder, there is the problem of high thermal
resistance.
[0007] On the other hand, as an example of using no solder for
bonding of an insulation plate and a radiation plate,
JP-A-11-269577 proposes a method of forming a metal base composite
material having a heat sink function by a chemical process
utilizing a reaction between a ceramic dispersion material and a
molten metal. This method suffers from the problem that since the
molten metal is high-pressure injected into the ceramic dispersion
material, expensive facilities are required, causing an increase of
cost. There may be considered a means to carry out the reaction
under impregnating the ceramic dispersion material with molten
metal, but in this case, there is the problem that the penetrating
speed is slow. In this method, the insulation substrate and the
metal base composite material as a radiation plate are connected
with a metal film or are connected with disposing a compound
containing a firing aid for the insulation substrate at the bonded
surface between the insulation substrate and the metal film, and
therefore the thermal conductivity is better than the case of
connecting with a solder. However, occurrence of cracks caused by
difference in thermal expansion coefficient between the insulation
plate of low thermal expansion coefficient and the metal film of
high thermal expansion coefficient or the metal film provided with
a compound containing firing aid for the insulation substrate
cannot sometimes be avoided.
[0008] As an example of using no metallic radiation plate, there
is, for example, an aluminum-silicon carbide composite material
known as a metal ceramics composite material. This composite
material is generally prepared by making a molded body (preform) of
ceramic particles, ceramic fibers, whiskers, etc., then
impregnating the preform with a molten metal and cooling it. As the
method for impregnating with molten metal there are various known
methods such as a method based on powder metallurgy, a method
according to high-pressure casting, e.g., die casting
(JP-A-5-508350), a melt forging method ("Material," Vol.36, No.1,
1997, pages 40-46), spontaneous penetrating method (JP-A-2-197368),
etc.
[0009] On the other hand, as power semiconductor apparatuses, there
are known, for example, those which comprise a semiconductor chip
comprising IGBT or the like, a metal base plate of about 4 mm thick
comprising copper or the like for radiating heat generated from the
semiconductor chip, and a ceramic plate of about 0.6 mm thick
comprising aluminum nitride or the like for insulating the
semiconductor chip from the metal base plate. A first metal
electrode of about 0.4 mm thick comprising copper or the like is
bonded to the upper surface of the ceramic plate with a first hard
solder of a given thickness. A semiconductor chip is bonded to the
upper surface of the metal electrode with a solder of about 0.2 mm
thick. A second metal electrode of about 0.2 mm thick comprising
copper or the like is bonded to the under surface of the ceramic
plate with a second solder of a given thickness. The under surface
of the ceramic plate and the second metal electrode are bonded to
the radiation plate with a solder or a hard solder.
[0010] However, there is a problem of low radiation property
because the insulating ceramic substrate and the radiation plate
are connected with a solder. Moreover, in the case of bonding the
insulating ceramic substrate and the metallic heat sink material
with a hard solder by active metal method or the like, cracks
caused by thermal stress at the time of bonding occur on the side
of the insulating ceramic substrate because of the great difference
in thermal expansion coefficient between both the materials.
Furthermore, a multi-layer type bonded body, which is bonded with a
solder and provided with a stress relaxing layer by a means other
than soldering, is low in endurance when exposed to thermal cycles
of cooling-heating and, besides, increases in thermal resistance
due to the increase of bonded interfaces which inhibits radiation.
Moreover, since stress relaxation is conducted by employing a
multi-layer structure, the number of production steps necessarily
increases, and, as a result, this causes an increase of production
cost. This is a serious problem.
[0011] On the other hand, as a method of bonding different members,
the applicant of the present application disclosed in application
JP-A-11-228245, utilizing an adhesive composition comprising
ceramic fine particles and a hard solder and capable of reducing
thermal stress. However, the object of the invention disclosed in
the above application is to inhibit the decrease of bonding
strength and the occurrence of cracks during the cooling operation,
mainly after bonding, in making members by bonding the different
members and need airtightness. The patent application makes no
mention which suggests improvement of endurance in a use
environment, such as increasing peeling resistance and effectively
inhibiting cracking at bonded portions under severe thermal cycles,
where high temperature-low temperature with cooling operation is
repeated many times, in applications such as heat sinks, laminated
radiation members and power semiconductor apparatuses. That is, of
course, the application does not have descriptions suggesting that
the products can function as a bonding layer of heat sinks,
laminated radiation members and power semiconductor
apparatuses.
SUMMARY OF THE INVENTION
[0012] As mentioned above, the object of the present invention is
to provide a laminated radiation member as a power semiconductor
apparatus which is substantially free from cracks generated due to
a difference in the thermal expansion coefficient between an
insulation substrate and a radiation plate, and which is excellent
in radiation properties and thermal cycle characteristics, and a
method for making the laminated radiation member.
BRIEF DESCRIPTION OF DRAWINGS
[0013] FIG. 1 is a schematic view of a water cooling module used in
the test.
[0014] FIG. 2 is a sectional view showing the construction of the
main part of the power semiconductor apparatus according to the
present invention.
[0015] FIG. 3 is a sectional view of a mold used in the production
examples of the power semiconductor apparatus according to the
present invention.
[0016] FIG. 4 is a sectional view showing the construction of the
main part of a conventional power semiconductor apparatus.
[0017] In the drawings, the reference numerals mean the
following:
[0018] (1) Circuit electrode; (2) Bonding layer (metal base
composite material); (3) Insulation substrate; (4) Radiation plate;
(5) Mixture of ceramic particles and active metal; (6) Mold; (7)
Solder; (8) Semiconductor chip; (9) Metal wire; (11) Heater; (12)
Module; (13) Flow path; (14) Water bath with pump; and (15) Flow
meter.
DETAILED DESCRIPTION OF THE INVENTION
[0019] As a result of intensive research conducted by the inventors
in an attempt to attain the above object, it has been found that a
laminated radiation member which is substantially free from
cracking caused by a difference in the thermal expansion
coefficient between an insulation substrate and a radiation plate,
and which is excellent in radiation properties, can be produced by
forming a metal base composite material using a specific ceramic
dispersion material and a hard solder, and bonding an insulation
substrate and a radiation plate with the metal base composite
material interposed between them. Thus, the present invention has
been accomplished.
[0020] That is, firstly, the present invention provides a laminated
radiation member comprising a radiation plate, an insulation
substrate bonded to the upper surface of the radiation plate and an
electrode provided on the upper surface of the insulation
substrate, wherein the radiation plate and the insulation substrate
are bonded with a metal base composite material in which ceramic
particles are dispersed and which is present between the radiation
plate and the insulation substrate.
[0021] The present invention further provides a laminated radiation
member, wherein the metal base composite material layer is produced
by providing ceramic dispersion particles which are previously
surface treated so as to assure wettability with a hard solder or a
metal, and reacting the ceramic particles with the molten solder or
metal and penetrated between the ceramic dispersion particles. The
reaction is carried out in the space between the radiation plate,
the bonding surface of which may be, if necessary, previously
surface treated so as to assure wettability with the solder or the
metal, and the insulation substrate, the bonding surface of which
may also be, if necessary, previously surface treated so as to
assure wettability with the solder or the metal.
[0022] The present invention further provides a laminated radiation
member, wherein the metal base composite material layer is produced
by reacting the ceramic dispersion particles with a hard solder or
a metal molten penetrated between the ceramic dispersion particles.
The solder or metal further contains at least one of an active
metal selected from the group consisting of Ti, Zr, Nb, Ta and Hf,
or, the active metal powders are previously dispersed in the space
between the ceramic dispersion particles. The laminated radiation
member is characterized in that the insulation substrate comprises
aluminum nitride or silicon nitride and further characterized in
that the insulation substrate and the electrode provided on the
upper surface of the insulation substrate are bonded with the metal
base composite material layer in which ceramic particles are
dispersed and which is interposed between the insulation substrate
and the electrode.
[0023] Secondly, the present invention provides a power
semiconductor apparatus comprising a circuit electrode, a laminated
radiation member comprising a radiation plate and an insulation
substrate, a semiconductor chip bonded to the circuit electrode
formed at the laminated radiation member and a metal wire
electrically connected to the semiconductor chip, the semiconductor
chip, the laminated radiation member and the circuit electrode
being sealed with an insulation sealer, characterized in that the
laminated radiation member is one of the laminated radiation
members enumerated above.
[0024] Thirdly, the present invention provides a method for making
a laminated radiation member comprising a radiation plate, an
insulation substrate bonded to the upper surface of the radiation
plate and an electrode provided on the upper surface of the
insulation substrate. The method includes a step of, if necessary,
previously surface treating a bonding surface of the radiation
plate and/or the insulation substrate so as to assure wettability
with a hard solder or a metal, a step of interposing ceramic
particles previously surface treated so as to assure wettability
with a hard solder or a metal between the radiation plate and the
insulation substrate, a step of disposing a hard solder above
and/or below the ceramic particles, a step of heating the solder to
a temperature higher than the melting point of the solder to melt
the solder, a step of penetrating the molten solder into spaces
between the ceramic particles to react the ceramic particles with
the solder to produce a metal base composite material, and a step
of bonding the radiation plate and the insulation substrate with
the metal base composite material present between them.
[0025] The present invention further provides a method for making a
laminated radiation member, wherein the surface treatment of the
ceramic particles and/or the insulation substrate and/or the
radiation plate for assuring the wettability, is a coating
treatment of at least a part of the surface with a metal. This
treatment is electroless plating, plating, sputtering, chemical
vapor deposition, vacuum deposition, or ionic plating. The method
for making a laminated radiation member comprising a radiation
plate, an insulation substrate bonded to the upper surface of the
radiation plate and an electrode provided on the upper surface of
the insulation substrate, is further characterized by including a
step of interposing the ceramic particles between the radiation
plate and the insulation substrate, a step of disposing a hard
solder containing at least one of an active metal selected from the
group consisting of Ti, Zr, Nb, Ta and Hf above and/or below the
ceramic particles, a step of heating the solder to a temperature
higher than the melting point of the solder to melt the solder, a
step of penetrating the molten solder into spaces between the
ceramic particles to react the ceramic particles with the solder to
produce a metal base composite material, and a step of bonding the
radiation plate and the insulation substrate with the metal base
composite material present between them.
[0026] The present invention further provides a method for making a
laminated radiation member comprising a radiation plate, an
insulation substrate bonded to the upper surface of the radiation
plate and an electrode provided on the upper surface of the
insulation substrate, including a step of interposing ceramic
particles and active metal powders selected from the group
consisting of Ti, Zr, Nb, Ta and Hf between the radiation plate and
the insulation substrate, a step of disposing a hard solder above
and/or below the ceramic particles, a step of heating the solder to
a temperature higher than the melting point of the solder to melt
the solder, a step of penetrating the molten solder into spaces
between the ceramic particles to react the ceramic particles with
the solder to produce a metal base composite material, and a step
of bonding the radiation plate and the insulation substrate with
the metal base composite material present between them.
[0027] In addition, the present invention provides a method for
making a laminated radiation member comprising a radiation plate,
an insulation substrate bonded to the upper surface of the
radiation plate and an electrode provided on the upper surface of
the insulation substrate, including a step of placing the
insulation plate in a solidification mold, a step of disposing
ceramic particles on one surface of the insulation substrate, a
step of pouring a molten metal into the solidification mold to
impregnate the ceramic particles with the molten metal and,
simultaneously with the impregnation, pouring the molten metal into
the portion where the ceramic particles are not present, and a step
of solidifying the molten metal to form the radiation plate in the
portion where the ceramic particles are not present. The method is
further characterized by including a step of bonding the insulation
substrate and the electrode with a hard solder or a metal base
composite material present between them, simultaneously with the
heat treatment for bonding the radiation plate and the insulation
substrate with the metal base composite material present between
them.
[0028] The present invention further provides a method for making a
laminated radiation member, characterized by further including a
step of bonding the electrode to the insulation substrate with the
hard solder or the metal base composite material by a heat
treatment at a temperature lower than the temperature at the
bonding step of the radiation plate and the insulation substrate,
the insulation substrate being bonded to the insulation substrate
with the metal base composite material present between them. A
method for making a laminated radiation member is also provided,
including a step of forming an electrode at a temperature lower
than the temperature at the bonding step of the radiation plate and
the insulation substrate on the insulation substrate bonded to the
radiation plate with the metal base composite material. A method
for making a laminated radiation member is provided, characterized
in that the step of forming the electrode at a lower temperature
comprises electroless plating, plating, sputtering, ionic plating,
chemical vapor deposition, vacuum deposition or flame spraying, or
combination of them.
[0029] Fourthly, the present invention further provides a method
for making a power semiconductor apparatus, including a step of
bonding a semiconductor chip to an electrode of a laminated
radiation member comprising a radiation plate, an insulation
substrate bonded to the upper surface of the radiation plate and an
electrode provided on the upper surface of the insulation
substrate, the radiation plate and said insulation substrate being
bonded to each other with a metal base composite material layer in
which ceramic particles are dispersed and which is present between
the radiation plate and the insulation substrate, a step of
electrically connecting metal wires to the semiconductor chip and
the electrode, respectively, a step of placing in a package the
semiconductor chip, the laminated radiation member and the circuit
electrode, and then providing an insulating sealer in the package.
Moreover, the present invention provides a method for making a
power semiconductor apparatus, characterized in that the laminated
radiation member is made by one of the methods mentioned above as
the third aspect.
[0030] According to the above methods of the present invention,
bonding of the insulation substrate and the radiation plate is
carried out with the metal base composite material layer present
therebetween. That is, the desired laminated radiation member and
power semiconductor apparatus, which are excellent in thermal
conductivity and thermal cycle characteristics, can be obtained by
a step of, if necessary, previously surface treating a bonding
surface of the radiation plate and/or the insulation substrate so
as to assure wettability with a hard solder or a metal, a step of
interposing ceramic particles previously surface treated so as to
assure wettability with a hard solder or a metal between the
radiation plate and the insulation substrate, a step of disposing a
hard solder above and/or below the ceramic particles, a step of
heating the solder to a temperature higher than the melting point
of the solder to melt the solder material, a step of penetrating
the molten solder into spaces between the ceramic particles to
react the ceramic particles with the solder to form a metal base
composite material low in thermal resistance and high in radiation
properties as a bonding layer, and a step of bonding the radiation
plate and the insulation substrate with the metal base composite
material present therebetween.
[0031] The present invention will be explained in more detail
below. The term "metal base composite material layer" in the
present specification means a layer comprising a composite material
which can be produced by melting and mixing a hard solder and
ceramic particles subjected to a specific surface treatment and
capable of reducing a specific thermal stress.
[0032] The laminated radiation member as a power semiconductor
apparatus according to the present invention can be made in the
following manner. A ceramic dispersing material previously
subjected to plating, such as SiC particles subjected to Ni--B
plating treatment, is placed on a plated surface of a radiation
plate which may be previously subjected to plating treatment. A
pressure is applied thereto to reduce the thickness and increase
packing rate of the particles. A hard solder such as a BA4004
(Al-10Si-1.5 Mg) sheet, which is an aluminum solder, is placed
thereon, and thereon is placed an insulation substrate (both
surfaces of which are subjected to plating treatment). Further
thereon is placed a ceramic dispersing material previously
subjected to plating treatment, such as the above SiC particles
subjected to Ni--B plating, followed by applying a pressure and
increasing packing rate of the particles. Thereon is placed a hard
solder such as a BA4004 (Al-10Si-1.5 Mg) sheet, which is an
aluminum solder, and further thereon is placed a thin copper sheet
for the formation of a circuit. Thereafter, the resulting stack is
subjected to a heat treatment at a given temperature in a vacuum
and the respective components are bonded with metal base composite
material layers present therebetween.
[0033] In the present invention, as the insulation substrate,
ceramic substrates having a thickness of 0.1-2 mm may be used,
preferably ones such as aluminum nitride and silicon nitride having
a thickness of 0.1-2 mm. Especially preferred are silicon nitride
substrates disclosed in JP-A-4-212441 and silicon nitride
substrates disclosed in JP. Appln. No.11-176479 filed on Jun. 23,
1999 from the points of thermal conductivity and assurance of
bonding strength.
[0034] The insulation substrate is preferably previously surface
treated for assuring wettability with the hard solder. As the
dispersing materials comprising ceramic particles which reduce
thermal stress, ceramic particles, such as SiC, AlN,
Si.sub.3N.sub.4, and Al.sub.2O.sub.3, having a particle diameter of
preferably 5-200 .mu.m, and more preferably, 10-50 .mu.m, may be
used. Usually, they are surface treated for assuring wettability
with the hard solder and uniformly spread over the insulation
substrate placed, for example, in a heat resistant container.
[0035] Of course, for bonding of the insulation substrate and the
radiation plate, a hard solder comprising at least one metal or
metal alloy selected from Al, Al alloy, copper and copper alloy is
used together with the ceramic dispersing material for the
formation of the bonding layer. The hard solder disposed above
and/or under the particles of the ceramic dispersing material is
interposed between the radiation plate and the insulation
substrate, followed by melting it to form a metal base composite
material which is the bonding layer. Usually, the hard solder is
placed on ceramic dispersing material uniformly spread over the
radiation plate disposed in a heat resistant container, and the
insulation substrate is further mounted thereon, followed by
heating and melting the solder to penetrate it into the spaces
between the particles of the ceramic dispersing material, and
solidifying it to form the desired bonding layer, namely, a metal
base composite material. This is preferably effected by heating to
a temperature 50-100.degree. C. higher than the melting point of
the above-mentioned metal or alloy in a furnace of vacuum or inert
atmosphere. The formation of the bonding layer by penetration of
the metal or the alloy can be completed in a shorter time as
compared with the similar conventional technique utilizing the
above reaction, and, hence, the retention time at the above
temperature can be not longer than 10 minutes.
[0036] In this case, the surface treatment of the insulation
substrate, the radiation plate and the dispersing material, which
is the ceramic particles, can comprise forming a layer of Ni, Cu,
Pd, or the like on the surface of the ceramic dispersing material
by electroless plating, plating, sputtering, ion plating, chemical
vapor deposition, vacuum deposition and the like. However, in the
case of using mainly Al alloy as the hard solder, electroless Ni
plating is suitable. In this case, the thickness of the plating
layer is preferably not more than 1 .mu.m, more preferably about
0.5 .mu.m. If the thickness is less than 0.5 .mu.m, penetration of
the solder does not properly occur, and if it is more than 1 .mu.m,
thermal conductivity may be deteriorated owing to production of an
intermetallic compound (Al.sub.3Ni) in a large amount.
[0037] For the assurance of wettability, it is also possible to add
an active metal such as Ti, Nb, Hf, Ta or Zr to the melt of metal
comprising the solder and forming a nitride, oxide or carbide of
these active metals on the surface of the insulation substrate and
the ceramic dispersing material. The amount of the active metal
added is suitably 0.5-20% by weight based on the solder. The metal
may be previously added to the solder, but when fine particles of
the active metal are previously added to the ceramic dispersing
material, since the amount of the active metal to be added can be
smaller, the thermal conductivity of the resulting composite
material can be maintained at high level. Thus, this is preferred.
This may be combined with the method of subjecting the surface of
the ceramic dispersing material to said plating treatment.
[0038] In reacting the ceramic dispersing material with the molten
hard solder to form a composite material, when those surface
treated by electroless plating, plating, sputtering, chemical vapor
deposition, vacuum deposition, or ion plating are used, local
exothermic reaction (burning synthesis reaction) takes place in the
case of contacting of the surface treatment layer with the molten
metal to cause reaction. For example, in the case of the surface
treatment layer being an electroless Ni--B plating and the molten
metal being an Al-based alloy, Ni aluminide is produced in
accordance with the reaction formula: Al+Ni.fwdarw.Al.sub.3Ni, and
the generated heat causes an exothermic reaction. Therefore,
substantially no pressure is needed, and the wettabilty between the
ceramic dispersing material/the molten metal is markedly improved
by the above-mentioned local exothermic reaction, and, as a result,
penetration speed of the molten metal is increased and the metal
base composite material can be formed in a very short time.
[0039] Furthermore, when an active metal is utilized for forming a
composite material of the ceramic dispersing material and the melt
of metal constituting the hard solder, since the active metal (Ti,
Zr, Nb, Ta, Hf or the like) is highly active for oxygen, nitrogen
and carbon, wettability between the ceramic dispersing material and
the molten metal is improved by dissolution of the active metal in
the molten metal to form a solid solution, and microscopically an
interface reaction with the melt containing the active metal takes
place on the surface of the ceramic dispersing material. That is,
in the case of the ceramic dispersing material being SiC and the
molten metal being Cu--Ti alloy, an exothermic reaction with
formation of TiC takes place according to the reaction of SiC
+Ti.fwdarw.TiC+Si (in copper). Thus, as above, this local
exothermic reaction increases penetration speed of the molten
metal, and the metal base composite material can be produced in a
very short time.
[0040] As the radiation plate, metallic plates such as of copper,
aluminum, silver, and the like, which are generally used for power
semiconductor apparatus, or plates made of alloys such as Cu--Be or
composite materials such as Cu--Mo, Cu--SiC, and the like may be
suitably used. In bonding the radiation plates made of composite
materials, it is preferred to use those surface treated by the
above methods in the same manner as of the dispersing materials
comprising ceramic particles. Formulation of the radiation plates
has no limitation, and those of the same as used for other power
semiconductor apparatuses can be used without any problems. As to
members other than those mentioned above, naturally those generally
used in power semiconductor apparatuses can be used without any
problems.
[0041] In the method of the present invention, the electrode can be
formed simultaneously with the bonding of the radiation plate and
the insulation substrate as in the case of Example 1, or it may be
separately formed. When the electrode is formed separately, it can
be solder-bonded using a hard solder which melts at lower than the
bonding temperature of the radiation plate and the insulation
substrate. In this case, the electrode may be bonded with the metal
base composite material layer in the same manner as in the bonding
of the radiation plate and the insulation substrate. Furthermore,
as a method of separate molding, the electrode can also be made
freshly by printing, flame spraying, plating or the like, instead
of by bonding.
[0042] The present invention will be explained in more detail by
the following examples. These examples should not be construed as
limiting the invention in any manner.
[0043] Measurements of characteristics in the examples were
conducted by the following methods.
[0044] Thermal Cycle Characteristics
[0045] In the air, a sample was subjected to cycles, one cycle of
which comprises holding the sample for 30 minutes in a low
temperature cryostat kept at -40.degree. C., then leaving the
sample for 10 minutes in a thermostat kept at 25.degree. C.,
furthermore raising the temperature of the thermostat to
125.degree. C. and holding the sample therein for 30 minutes, and
lowering the temperature of the thermostat to 25.degree. C. and
leaving the sample therein for 10 minutes. Five samples were
prepared for each kind of samples, and the thermal cycle
characteristics of the respective samples were evaluated in terms
of the number of cycles when even one of the five had cracks in the
insulation substrate or showed separation at the bonded portion of
the radiation plate.
[0046] Heat Resistant Characteristics
[0047] A water-cooling module as shown in FIG. 1 was made, and a
heater was adhered to the surface of the circuit-formed portion of
the insulation substrate with an Ag paste. Cooling water of
24.degree. C. was circulated at a flow rate of 2 l/min, and
temperatures of the heater surface and the interface of
sample/running water were measured, and heat resistance of the
sample was calculated. Relative evaluation of the heat resistance
was conducted with assuming the resistance of Comparative Example 1
to be 1.0.
EXAMPLE 1
[0048] Ni Plating Method/Upper Electrode Simultaneous Bonding
[0049] As the insulation substrate, a silicon nitride insulation
substrate of 50 mm.times.40 mm.times.0.3 mm having a thermal
conductivity of 90 W/mK was prepared by adding Y.sub.2O.sub.3 and
MgO as firing assistants to a commercially available silicon
nitride powder and firing the mixture at a given temperature for a
given period. Separately, a radiation plate (80 mm.times.50
mm.times.3 mm) comprising a Cu--SiC composite material and having a
thermal conductivity of 250 W/mK was prepared by the method
disclosed in JP-A-11-029379.
[0050] Separately, the surface of commercially available SiC
particles (average particle diameter: about 50 .mu.m) was subjected
to Ni--B plating at a thickness of about 0.5 .mu.m by wet
electroless plating. On the other hand, both sides of the above
silicon nitride insulation substrate were subjected to electroless
Ni--B plating at a thickness of about 1 .mu.m. One side of the
above Cu--SiC radiation plate was also subjected to electroless
Ni--B plating at a thickness of about 1 .mu.m. The above Ni--B
plated SiC particles were disposed on the Ni--B plated surface of
the Cu--SiC radiation plate, followed by applying a pressure to
reduce the thickness to improve the packing rate of the particles.
On the upper surface thereof was placed an Al solder sheet (BA4004:
Al-10Si-1.5 Mg) and thereon was placed the silicon nitride
insulation substrate subjected to Ni--B plating on both the sides.
Furthermore, Ni--B plated SiC particles were disposed on the upper
surface thereof, followed by applying a pressure to reduce the
thickness to improve the packing rate of the particles. On the
upper surface thereof was placed an Al solder sheet (BA4004:
Al-10Si-1.5 Mg). Then, a copper sheet 0.3 mm thick was placed on
the upper surface of the solder sheet.
[0051] Then, the resulting stack was heated to 700.degree. C. at a
heating rate of 15.degree. C./min in a vacuum of 0.00133 Pa and
kept at 700.degree. C. for 3 minutes, and then slowly cooled to
room temperature at a cooling rate of 2.degree. C./min to prepare a
bonded body (laminated radiation member). In this bonded body, the
Cu--SiC radiation plate and the silicon nitride insulation
substrate were bonded with a composite material layer of
SiC/aluminum solder present between the radiation plate and the
substrate, and the silicon nitride insulation substrate and the
uppermost copper sheet 0.3 mm thick were also bonded with a
composite material layer of SiC/aluminum solder.
[0052] Then, a resist for the formation of circuits was printed on
the whole surface of the thus obtained laminated radiation member,
then only the portions which were not etched later were selectively
cured, the uncured portions were removed, and the exposed copper
was etched with an aqueous cupric chloride solution to form a
circuit pattern of the uppermost copper sheet of the laminated
radiation member. Furthermore, this was washed with an aqueous acid
ammonium fluoride solution and additionally washed with water
several times to remove the solder between the circuits.
[0053] Then, the resist was peeled off and finally the surface of
the uppermost copper sheet (=circuit sheet) was subjected to Ni--P
plating to form a protective layer, thereby making a laminated
radiation member.
EXAMPLE 2
[0054] Ni Plating Method/Upper Electrode Simultaneous Bonding
[0055] A laminated radiation member was made in the same manner as
in Example 1, except that a commercially available pure copper
plate (oxygen-free copper of pure copper composition or tough pitch
copper, 80.times.50.times.3 mm radiation plate) having a thermal
conductivity of 390 W/mK was prepared in place of preparing the
Cu--SiC composite material (80.times.50.times.3 mm: radiation
plate), and a commercially available Al203 powder (average particle
diameter: about 40 .mu.m) was used in place of the commercially
available SiC particles (average particle diameter: about 50
.mu.m).
EXAMPLE 3
[0056] Powder Active Metal Method/Upper Electrode Simultaneous
Bonding
[0057] A silicon nitride insulation substrate of
50.times.40.times.0.3 mm having a thermal conductivity of 90 W/mK
was prepared by adding Y.sub.2O.sub.3 and MgO as firing assistants
to a commercially available silicon nitride powder and firing the
mixture at a given temperature for a given period. Separately, a
commercially available pure copper plate (oxygen-free copper of
pure copper composition or tough pitch copper, 80.times.50.times.3
mm: radiation plate) having a thermal conductivity of 390 W/mK was
prepared.
[0058] On the other hand, a mixture of AlN pulverized powder
(average particle diameter: 50 .mu.m) and Ti powder (average
particle diameter: 44 .mu.m) was placed, followed by applying a
pressure to reduce the thickness to improve the packing rate of the
particles, and this was placed on the upper surface of the above
radiation plate. On the upper surface thereof was placed a
commercially available silver solder sheet (BAg-8: Ag-28Cu) and
thereon was placed the above silicon nitride insulation substrate.
On the upper surface thereof, was further placed a mixture of AlN
pulverized powder (average particle diameter: 50 .mu.m) and Ti
powder, followed by applying pressure to reduce the thickness to
improve packing rate of the particles, and moreover, on the upper
surface thereof was placed a commercially available silver solder
sheet (BAg-8: Ag-28Cu). Furthermore, a copper sheet of 0.3 mm thick
was placed on the upper surface thereof.
[0059] Then, the resulting stack was kept at 800.degree. C. for 3
minutes in a vacuum of 0.00133 Pa and then slowly cooled to prepare
a bonded body (laminated radiation member). In this bonded body,
the Cu--SiC radiation plate and the silicon nitride insulation
substrate were bonded with a composite material layer of AlN/silver
solder present between the radiation plate and the substrate, and
the silicon nitride insulation substrate and the uppermost copper
sheet 0.3 mm thick were also bonded with a composite material layer
of AlN/silver solder present therebetween.
[0060] Then, a resist for the formation of circuits was printed on
the whole surface of the thus obtained laminated radiation member,
then only the portions which were not etched later were selectively
cured, then the uncured portions were removed, and the exposed
copper was etched with an aqueous cupric chloride solution to form
a circuit pattern of the uppermost copper sheet of the laminated
radiation member. Furthermore, this was washed with an aqueous acid
ammonium fluoride solution and additionally washed with water
several times to remove the solder between the circuits.
[0061] Then, the resist was peeled off and finally the surface of
the uppermost copper sheet (=circuit sheet) was subjected to Ni--P
plating to form a protective layer, thereby obtaining a laminated
radiation member.
EXAMPLE 4
[0062] Solid Solution Active Metal method/Upper Electrode
Simultaneous Bonding
[0063] A silicon nitride insulation substrate of
50.times.40.times.0.3 mm having a thermal conductivity of 90 W/mK
was prepared by adding Y.sub.2O.sub.3 and MgO as firing assistants
to a commercially available silicon nitride powder and firing the
mixture at a given temperature for a given period. Separately, a
commercially available pure copper plate (oxygen-free copper of
pure copper composition or tough pitch copper, 80.times.50.times.3
mm: radiation plate) having a thermal conductivity of 390 W/mK was
prepared.
[0064] On the other hand, a commercially available SiC particles
(average particle diameter: 50 .mu.m) were placed, followed by
applying pressure to reduce the thickness to improve packing rate
of the particles, and this was placed on the upper surface of the
above radiation plate. On the upper surface thereof was placed a
Cu--Ti hard solder (Cu-15Ti) sheet and thereon was further placed
the above commercially available SiC particles On the upper surface
thereof, were further placed commercially available SiC particles
(average particle diameter: 50 .mu.m), followed by applying
pressure to reduce the thickness to improve packing rate of the
particles, and moreover, on the upper surface thereof was placed a
Cu--Ti hard solder (Cu-15Ti) sheet. Furthermore, a copper sheet 0.3
mm thick was placed on the upper surface thereof.
[0065] Then, the resulting stack was kept at 1000.degree. C. for 30
minutes in a vacuum of 0.00133 Pa and then slowly cooled to prepare
a bonded body (laminated radiation member). In this bonded body,
the pure copper radiation plate and the silicon nitride insulation
substrate were bonded with a composite material layer of SiC/Cu--Ti
solder present between the radiation plate and the substrate, and
the silicon nitride insulation substrate and the uppermost copper
sheet of 0.3 mm thick were also bonded with a composite material
layer of SiC/Cu--Ti solder present therebetween.
[0066] Then, a resist for the formation of circuits was printed on
the whole surface of the thus obtained laminated radiation member,
then only the portions which were not etched later were selectively
cured, then the uncured portions were removed, and the exposed
copper was etched with an aqueous cupric chloride solution to form
a circuit pattern of the uppermost copper sheet of the laminated
radiation member. Furthermore, this was washed with an aqueous acid
ammonium fluoride solution and additionally washed with water
several times to remove the solder between the circuits.
[0067] Then, the resist was peeled off and finally the surface of
the uppermost copper sheet (=circuit sheet) was subjected to Ni--P
plating to form a protective layer, thereby obtaining a laminated
radiation member.
EXAMPLE 5
[0068] Ni Plating Method/Upper Electrode Simultaneous Bonding
[0069] A sample was made in the same manner as in Example 1, except
that silicon nitride insulation substrate of
50.times.40.times.0.635 mm having a thermal conductivity of 180
W/mK was prepared by adding Y.sub.2O.sub.3 as firing assistants to
a commercially available silicon nitride powder and firing the
mixture at a given temperature for a given period.
EXAMPLE 6
[0070] Preparation of Upper Electrode Using Hard Solder Having a
Melting Point Lower Than Hard Solder for Bonding to Radiation
Plate
[0071] A silicon nitride insulation substrate of
50.times.40.times.0.3 mm having a thermal conductivity of 90 W/mK
was prepared by adding Y.sub.2O.sub.3 and MgO as firing assistants
to a commercially available silicon nitride powder and firing the
mixture at a given temperature for a given period. Separately, a
Cu--SiC composite material (80.times.50.times.3 mm: radiation
plate) having a thermal conductivity of 250 W/mK was prepared by
the method disclosed in JP-A-11-029379.
[0072] Separately, the surface of commercially available SiC
particles (average particle diameter: 50 .mu.m) was subjected to
Ni--B plating at a thickness of about 0.5 .mu.m by wet electroless
plating. On the other hand, one side of the above silicon nitride
insulation substrate was subjected to electroless Ni--B plating at
a thickness of about 1 .mu.m. Furthermore, one side of the above
Cu--SiC composite material radiation plate was also subjected to
electroless Ni--B plating at a thickness of about 1 .mu.m. The
above Ni--B plated SiC particles were disposed on the Ni--B plated
surface of the radiation plate, followed by applying pressure to
reduce the thickness to improve packing rate of the particles. On
the upper surface thereof was placed a silver hard solder sheet
(BAg-8: Ag-28Cu) and thereon was further placed the silicon nitride
insulation substrate subjected to Ni--B plating on one side so that
the Ni--B plated surface contacted the solder sheet.
[0073] Then, the resulting stack was kept at 800.degree. C. for 3
minutes in a vacuum of 0.00133 Pa and then slowly cooled to prepare
a bonded body (laminated radiation member). In this bonded body,
the Cu--SiC radiation plate and the silicon nitride insulation
substrate were bonded with a composite material layer of SiC/silver
solder present between the radiation plate and the substrate.
[0074] Then, an Al solder (BA4004: Al-10Si-1.5 Mg) sheet was placed
on the silicon nitride insulation substrate of the laminated
radiation member, and thereon was placed a copper sheet 0.3 mm
thick, followed by heat treating them in this state at 700.degree.
C. for 3 minutes in vacuum in this state to obtain a composite
bonded member.
[0075] Then, a resist for the formation of circuits was printed on
the whole surface of the thus obtained laminated radiation member,
then only the portions which were not etched later were selectively
cured, then the uncured portions were removed, and the exposed
copper was etched with an aqueous cupric chloride solution to form
a circuit pattern of the uppermost copper sheet of the laminated
radiation member. Furthermore, this was washed with an aqueous acid
ammonium fluoride solution and additionally washed with water
several times to remove the solder between the circuits.
[0076] Then, the resist was peeled off and finally the surface of
the uppermost copper sheet (=circuit sheet) was subjected to Ni--P
plating to form a protective layer, thereby obtaining a laminated
radiation member.
EXAMPLE 7
[0077] Preparation of Upper Electrode Using Composite Hard Solder
Having a Melting Point Lower Than Hard Solder for Bonding to
Radiation Plate
[0078] A bonded body (laminated radiation member) in which the
Cu--SiC radiation plate and the silicon nitride insulation
substrate were bonded with a composite material layer of SiC/silver
solder present between the radiation plate and the substrate was
made in the same manner as in Example 6, except that both sides of
the silicon nitride insulation substrate were subjected to
electroless Ni--B plating at a thickness of about 1 .mu..
[0079] Then, the above Ni--B plated SiC pulverized powder was
placed on the surface of the silicon nitride insulation substrate
which was subjected to electroless Ni--B plating of about 1 .mu.m
thick in the above laminated radiation member, followed by applying
pressure thereto to reduce the thickness to improve packing rate of
particles. On the upper surface thereof was placed a commercially
available aluminum solder sheet (BA4004: Al-10Si-1.5 Mg), and on
the upper surface thereof was further placed a copper sheet of 0.3
mm thick.
[0080] Then, the resulting stack was kept at 700.degree. C. for 3
minutes in a vacuum of 0.00133 Pa and then slowly cooled to prepare
a bonded body (laminated radiation member). In this bonded body,
the Cu--SiC radiation plate and the silicon nitride insulation
substrate were bonded with a composite material layer of SiC/silver
solder present between the radiation plate and the substrate, and
the silicon nitride insulation substrate and the uppermost copper
sheet 0.3 mm thick were bonded with a composite material layer of
SiC/aluminum solder present between the substrate and the copper
sheet.
[0081] Then, a resist for the formation of circuits was printed on
the whole surface of the thus obtained laminated radiation member,
then only the portions which were not etched later were selectively
cured, then the uncured portions were removed, and the exposed
copper was etched with an aqueous cupric chloride solution to form
a circuit pattern of the uppermost copper sheet of the laminated
radiation member. Furthermore, this was washed with an aqueous acid
ammonium fluoride solution and additionally washed with water
several times to remove the solder between the circuits.
[0082] Then, the resist was peeled off and finally the surface of
the uppermost copper sheet (=circuit sheet) was subjected to Ni--P
plating to form a protective layer, thereby obtaining a laminated
radiation member.
EXAMPLE 8
[0083] Active Metal Method, Cu Casting
[0084] A silicon nitride insulation substrate of
50.times.40.times.0.3 mm having a thermal conductivity of 90 W/mK
was prepared by adding Y.sub.2O.sub.3 and MgO as firing assistants
to a commercially available silicon nitride powder and firing the
mixture at a given temperature for a given period.
[0085] Separately, pressure was applied to a mixture comprising
commercially available SiC particles (average particle diameter: 50
.mu.m) and commercially available Ti powder (average particle
diameter: 44 .mu.m) to reduce the thickness to improve packing rate
of the particles, and this was placed on the upper surface of the
above radiation plate. This was put in a mold as shown in FIG. 3
and heated to 1100.degree.C., followed by casting a copper melt
therein and cooling it to obtain a laminated radiation member.
[0086] In this laminated member, the copper radiation plate of
about 80.times.50.times.3 mm and the silicon nitride insulation
substrate were bonded with a composite material layer of SiC/copper
present between the radiation plate and the substrate.
[0087] On the silicon nitride insulation substrate of the laminated
radiation member was printed a commercially available Ag--Cu--Ti
hard solder (Ag-35Cu-1.7Ti) paste at a given thickness, and thereon
was placed a copper sheet 0.3 mm thick, followed by heat treating
them in this state at 850.degree. C. for 10 minutes in a vacuum of
0.00133 Pa to obtain a composite bonded member.
[0088] Then, a resist for the formation of circuits was printed on
the whole surface of the thus obtained laminated radiation member,
then only the portions which were not etched later were selectively
cured, then the uncured portions were removed, and the exposed
copper was etched with an aqueous cupric chloride solution to form
a circuit pattern of the uppermost copper sheet of the laminated
radiation member. Furthermore, this was washed with an aqueous acid
ammonium fluoride solution and additionally washed with water
several times to remove the solder material between the
circuits.
[0089] Then, the resists were peeled off and finally the surface of
the uppermost copper sheet (=circuit sheet) was subjected to Ni--P
plating to form a protective layer, thereby making a laminated
radiation member.
EXAMPLES 9 and 10
[0090] Plating, Flame Spraying
[0091] A silicon nitride insulation substrate of
50.times.40.times.0.3 mm having a thermal conductivity of 90 W/mK
was prepared by adding Y.sub.2O.sub.3 and MgO as firing assistants
to a commercially available silicon nitride powder and firing the
mixture at a given temperature for a given period. Separately, a
Cu--SiC composite material (80.times.50.times.3 mm: radiation
plate) having a thermal conductivity of 250 W/mK was prepared by
the method disclosed in JP-A-11-029379.
[0092] Separately, surface of commercially available SiC particles
(average particle diameter: 50 .mu.m) was subjected to Ni--B
plating at a thickness of about 0.5 .mu.m by wet electroless
plating. On the other hand, one side of the above silicon nitride
insulation substrate was subjected to electroless Ni--B plating at
a thickness of about 1 .mu.m. Furthermore, one side of the above
Cu--SiC composite material radiation plate was also subjected to
electroless Ni--B plating at a thickness of about 1 .mu.m. The
above Ni--B plated SiC particles were disposed on the Ni--B plated
surface of the radiation plate, followed by applying pressure to
reduce the thickness to improve packing rate of the particles. On
the upper surface thereof was placed a commercially available
aluminum hard solder sheet (BA4004: Al-10Si-1.5 Mg) and thereon was
further placed the silicon nitride insulation substrate subjected
to Ni--B plating on one side so that the Ni--B plated surface
contacted the solder sheet.
[0093] Then, the resulting stack was kept at 700.degree. C. for 3
minutes in a vacuum of 0.00133 Pa and then slowly cooled to prepare
a bonded body (laminated radiation member). In this bonded body,
the Cu--SiC radiation plate and the silicon nitride insulation
substrate were bonded with a composite material layer of
SiC/aluminum hard solder present between the radiation plate and
the substrate.
[0094] Then, masking was carried out on the silicon nitride
insulation substrate, followed by carrying out wet electroless
copper plating at lower than 100.degree. C. to form a copper
circuit pattern. This was referred to as the sample of Example 9.
Masking was carried out on the portions other than circuit pattern
and an Al--Si layer of about 50 .mu.m was flame sprayed, followed
by carrying out HVOF flame spraying of Cu at a thickness of about
0.3 mm. After removing the masking, the surface of the copper
circuit was made smooth by mechanical working to form a copper
circuit. This was referred to as the sample of Example 10.
COMPARATIVE EXAMPLE 1
[0095] A silicon nitride insulation substrate of
50.times.40.times.0.3 mm having a thermal conductivity of 90 W/mK
was prepared by adding Y.sub.2O.sub.3 and MgO as firing assistants
to a silicon nitride powder and firing the mixture at a given
temperature for a given period. Then, on both sides thereof was
printed a commercially available Ag--Cu--Ti hard solder
(Ag-35Cu-1.7Ti) paste at a given thickness, and on both sides
thereof were placed copper sheets of 0.3 mm thick, followed by heat
treating them in this state at 850.degree. C. for 10 minutes in a
vacuum of 0.00133 Pa to obtain a composite bonded body.
[0096] Then, a resist for the formation of circuits were printed on
one side of the composite bonded body and was cured, then the
copper was etched with an aqueous cupric chloride solution to form
a circuit pattern. Furthermore, this was washed with an aqueous
acid ammonium fluoride solution and additionally washed with water
several times to remove the solder material between the circuits.
Then, the surface of the metal portion was subjected to Ni--P
plating to form a protective layer, thereby making a circuit
substrate.
[0097] Then, the surface of the circuit substrate on which no
circuits were formed and a Cu--SiC composite material made by the
method disclosed in JP-A-11-029379 (80 .times.50.times.3 mm:
radiation plate) were bonded by soldering.
COMPARATIVE EXAMPLE 2
[0098] Radiation Plate/Hard Solder/Substrate/Hard
Solder/Circuit
[0099] A silicon nitride insulation substrate of
50.times.40.times.0.3 mm having a thermal conductivity of 90 W/mK
was prepared by adding Y.sub.2O.sub.3 and MgO as firing assistants
to a commercially available silicon nitride powder and firing the
mixture at a given temperature for a given period. Separately, a
Cu--SiC composite material having a thermal conductivity of 250
W/mK was made by the method disclosed in JP-A-11-029379
(80.times.50.times.3 mm: radiation plate).
[0100] A commercially available Ag--Cu--Ti hard solder
(Ag-35Cu-1.7Ti) paste was printed on the above radiation plate at a
given thickness, and thereon was placed the above silicon nitride
insulation substrate. Further, thereon was printed the commercially
available Ag--Cu--Ti solder (Ag-35Cu-1.7Ti) paste at a given
thickness and thereon was further placed a copper sheet 0.3 mm
thick.
[0101] Then, this was kept at 850.degree. C. for 10 minutes in a
vacuum of 0.00133 Pa, followed by slow cooling to obtain a bonded
body (laminated radiation member). In this bonded body, the Cu--SiC
radiation plate and the silicon nitride insulation substrate were
bonded with the Ag--Cu--Ti solder layer present therebetween, and
the silicon nitride insulation substrate and the uppermost copper
sheet 0.3 mm thick were also bonded with the Ag--Cu--Ti solder
layer present therebetween.
[0102] Then, a resist for formation of circuits was printed on the
whole surface of the thus obtained laminated radiation member, then
only the portions which were not etched later were selectively
cured, then the uncured portions were removed, and the exposed
copper was etched with an aqueous cupric chloride solution to form
a circuit pattern of the uppermost copper sheet of the laminated
radiation member. Furthermore, this was washed with an aqueous acid
ammonium fluoride solution and additionally washed with water
several times to remove the solder material between the
circuits.
[0103] Then, the resist was peeled off and finally the surface of
the uppermost copper sheet (=circuit sheet) was subjected to Ni--P
plating to form a protective layer, thereby making a laminated
radiation member.
COMPARATIVE EXAMPLE 3
[0104] A sample was prepared in the same manner as in Comparative
Example 2, except that an aluminum nitride insulation substrate of
50.times.40.times.0.635 mm having a thermal conductivity of 180
W/mK was prepared by adding Y.sub.2O.sub.3 as a firing assistant to
a commercially available aluminum nitride powder and firing the
mixture at a given temperature for a given period.
[0105] The thus obtained samples were subjected to a thermal cycle
characteristics test and a heat resistance test. The results are
shown in Table 1. The results of the heat resistance test are shown
by a relative value assuming the value obtained in Comparative
Example 1 to be 1.0.
1TABLE 1 Interface of Timing of Radiation Interface of Thermal
Thermal Ex- bonding plate & Radiation plate & Circuit cycle
resistance am- Pretreat- upper Radiation insulation Insulation
insulation elec- charac- (Standard- ple ment electrode plate
substrate substrate substrate trode teristics ized value) 1
Ni-plating Simulta- Cu-SiC SiC/Al hard SN SiC/Al hard Cu 3200 0.9
neously solder solder 2 Ni-plating Simulta- Cu Al.sub.2O.sub.3/Al
hard SN Al.sub.2O.sub.3/Al hard Cu 2600 0.7 neously solder solder 3
Powder Simulta- Cu AiN/Ag hard SN AiN/Ag hard Cu 3200 0.8 active
neously solder solder metal 4 Solid Simulta- Cu SiC/CuTi SN
SiC/CuTi hard Cu 3000 0.8 solution neously hard solder solder
active metal 5 Ni-plating Simulta- Cu--SiC SiC/Al hard SN SiC/Al
hard Cu 1800 0.9 neously solder solder Ex- am- ple Interface of
& Timing of Radiation Interface of Thermal Thermal Com. bonding
plate & Radiation plate & Circuit cycle resistance Ex-
Pretreat- upper Radiation insulation Insulation insulation elec-
charac- (Standard- am. ment electrode plate substrate substrate
substrate trode teristics ized value) 6 Low-Temp. Later Cu--SiC
SiC/Ag hard SN Al hard solder Cu 2000 0.9 hard solder solder for
electrode 7 Composite " Cu--SiC SiC/Ag hard SN SiC/Al hard Cu 3200
0.8 hard solder solder solder for electrode 8 Casting of " Cu
SiC/Cu com- SN AgCuTi hard Cu 2600 0.7 molten Cu posite solder
material 9 Plating " Cu SiC/Al hard SN -- Cu 1800 0.7 solder 10
Flame " Cu--SiC SiC/Al hard SN Al--Si Cu 2200 0.8 spraying solder
Com. -- -- Cu--SiC Solder + Cu + SN AgCuTi hard Cu 500 1.0 Exa.
AgCuTi solder 1 hard solder 2 -- -- Cu--SiC AgCuTi hard SN AgCuTi
hard Cu 100 0.8 solder solder 3 -- -- Cu--SiC AgCuTi hard SN AgCuTi
hard Cu 10 0.8 solder solder
EXAMPLE 11
[0106] A commercially available IGBT element (power semiconductor)
made of Si was bonded to the circuit electrode of the laminated
radiation member made in Example 1 by low-temperature soldering.
Then, a metal wire was electrically connected to the terminal of
the IGBT element by wire bonding method and simultaneously a metal
wire was also similarly connected to the circuit electrode.
Thereafter, the laminated radiation member on which the IGBT
element was mounted was put in a package. Then, a commercially
available silicone gel for potting was poured into the above
package and cured, followed by sealing the package to enhance the
electrical insulation of the laminated radiation member on which
the IGBT element was mounted and to increase the mechanical
reliability, thereby obtaining a power semiconductor apparatus.
[0107] As mentioned above, the laminated radiation member and the
power semiconductor apparatus according to the present invention
show substantially no cracking caused by the difference between the
thermal expansion coefficient of the insulation substrate, the
metal base composite material and the radiation plate, because the
radiation plate and the insulation substrate are bonded with a
metal base composite material which is high in heat resistance and
radiation properties. This includes a step of, if necessary,
previously surface treating a bonding surface of the radiation
plate and/or the insulation substrate to assure wettability with a
solder material or a metal, a step of interposing ceramic particles
previously surface treated to assure wettability with a solder
material or a metal between the radiation plate and the insulation
substrate, a step of disposing a solder material above and/or below
the ceramic particles, a step of heating the solder material to a
temperature higher than the melting point of the solder material to
melt the solder material, a step of penetrating the molten solder
material into spaces between the ceramic particles to react the
ceramic particles with the solder material to produce the metal
base composite material layer. Furthermore, according to the
production method of the present invention as mentioned above, a
laminated radiation member and a power semiconductor apparatus
having the above properties can be obtained.
* * * * *