JP2002222905A - Power module, composite substrate thereof and bonding solder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power module, a composite substrate used therefor and a bonding solder therefor which has a little bond deformation, a high bond yield and a high bond zone reliability. SOLUTION: The power module has a ceramic board having a circuit board on one side and a radiation board on the other side, a heat sink board bonded to the radiation board through a metal bond A and a semiconductor power elements bonded to the circuit board through a metal bond B. Either of the metal bonds A, B is an Ag-Cu-Sn, Ag-Cu-In or Ag-Cu-Sn-In type Ag based alloy having a melting point of 500-600 deg.C and the other is solder, or either of the bonds A, B is an Ag based alloy containing Cu 10-30 wt.% and either Sn or in or both 20-40 wt.%. A composite board and a solder therefor are used for the module.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power module on which a novel semiconductor power element is mounted, a composite substrate thereof, and a bonding material.

[0002]

2. Description of the Related Art A power module according to the present invention has a ceramic substrate provided with a circuit board on one surface and a radiator plate on the other surface, a heat sink substrate on the radiator plate, and a semiconductor power supply on the circuit plate. A structure in which elements are bonded is known. The joining of the heat sink substrate and the semiconductor power element is not simultaneous, but is usually done separately in terms of the production process. These joints are made by soldering as is known in Journal of the Japan Society of Mechanical Engineers, Vol.103, No.978, pages 44-45 (May 2000) and others.

[0003] Japanese Patent Application Laid-Open No. 7-283339 discloses that a metal supporting plate and an insulating plate are bonded at a melting point of 450 ° C.
45% Ag, 15% Zn, 24% Cd, 16% C at 0 ° C
bonding with a hard solder of a u alloy, a semiconductor element having a melting point of less than 450 ° C. and a melting point of about 180 ° C., 5% Sn, 0.6%
It is disclosed that the joint is made by soft solder of Ni, 0.05% P and the balance Sn.

[0004]

Since the semiconductor power element and the heat sink substrate are individually joined, solders having different melting points are used for joining them. That is, a high melting point solder is used as the solder to be joined first. In addition, as solder, Pb (lead) added with Sn (tin) is used.
b-based solder and Sn-based solder obtained by adding Sb (antimony) to Sn (tin) are known. The joining of power modules using these solders has the following problems. (a) It is difficult to select a solder having a large difference in melting point, and the first solder joint is damaged during the second solder joint. As a result, the production yield and the reliability of the power module have been reduced. This problem is more remarkable when the production speed is increased, because the heat sink substrate has a large heat capacity, that is, the heat sink substrate has a structure having cooling fins and water passages for water cooling. (b) Although it is possible to provide a maximum melting point difference of about 140 ° C. with Pb-based solder, Pb-free solder is desired due to environmental problems. On the other hand, in a Pb-less Sn-based solder, the achievable difference in melting point is a smaller value. (c) Sn-based solder (for example, Sn-10% S)
b The melting point of the solder is 267 ° C), and the other solder is Au.
System solder (for example, the melting point of Au-3.15% Si solder is 3
63 ° C.) is physically possible, but Au
Since the system solder was expensive and required to provide friction at the time of joining, it was not practical. (d) Although it is physically possible to select Sn-based solder for one and silver brazing or active brazing material for the other, since the melting points of these brazing materials are too high, the joining of the semiconductor power element is performed. When used in semiconductor devices, they damage semiconductor power devices. Further, when used for bonding a heat sink substrate, there is a problem that a large warp deformation is caused to the heat sink substrate. Therefore, it is possible, but not realistic, to select a large melting point difference.

[0005] As described above, the conventional joining of power modules has a great problem in terms of yield and reliability during production.

Further, in the joining of the metal support plate and the insulating plate described in the above-mentioned publication, the deformation is large because the joining temperature is high.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power module, a composite board thereof, and a brazing material for the power module, which have a small bonding deformation, a high bonding yield, and a high reliability of the bonding portion.

[0008]

According to the present invention, there is provided a ceramic substrate having a circuit board on one surface and a heat sink on the other surface, a heat sink substrate joined to the heat sink by a metal joining material A, In a power module having a semiconductor power element bonded to a circuit board by a metal bonding material B, one of the metal bonding materials A and B has a melting point of 500 to 600 ° C. and is composed of Ag—Cu—Sn.
System, an Ag-Cu-In-based or Ag-Cu-Sn-In-based Ag-based alloy, the other being made of solder,
One of the metal bonding materials A and B is, by weight,
It is made of an Ag-based alloy containing 10 to 30% of Cu and one or two of Sn and In in total of 20 to 40%, and the other is made of solder. The heat sink substrate is mainly made of copper and copper oxide. And the metal bonding materials A and B
Is one of which has a melting point of 500 to 600 ° C.
It is characterized by being made of a g-base alloy and the other being made of solder.

In the present invention, the melting point is the temperature at which the alloy begins to melt. The composite material mainly composed of copper and copper oxide contains 20 to 80% by weight of copper, preferably 30 to 70% by weight.
%, More preferably 40-60% and copper oxide 20-80
%, Preferably an alloy having the same as copper.
g, Zn, Ni, Ti, Cr, Fe, Co, Zr, H
One or more of f, V, Nb, Ta, W, and Mo are 5% or less in total, preferably 2% or less, and more preferably 0.1% or less.
It can contain 5% or less, and these are used as a melting material, a sintering material, and a plastic working material thereof.

The melting point of the Ag-based alloy is two times lower than the melting point of the solder.
Pb having a melting point of 180 to 330 ° C. which is higher by 00 to 400 ° C., preferably 250 to 360 ° C.
It is preferable that the heat sink substrate is made of a cooling fin or a cooling body having a water passage formed therein, and the ceramic substrate is made of an alumina substrate or an aluminum nitride substrate.

That is, according to the present invention, a heat sink substrate is bonded to a heat sink using a metal bonding material A, and a semiconductor power element is bonded to a circuit board using a metal bonding material B. One of them is made of solder and the other is made of low-temperature brazing material, so that the metal joining materials A and B have a large difference in melting point. Then, by using a low-temperature brazing material having a high melting point for the first joining and a solder having a low melting point for the second joining, the first joint is prevented from being damaged at the time of the second joining. As a result, it is possible to realize a power module having a high bonding yield at the time of production and high reliability of the bonding portion. In addition, even if the heat sink substrate has a structure having cooling fins and water passages for water cooling and having a large heat capacity, it is not necessary to care much about the temperature distribution of the power module in the joining environment, and the production speed at the time of joining may be increased. The result was obtained.

In order to prevent damage to the first joint at the time of solder joining and to prevent damage to the semiconductor power element and large warping deformation to the heat sink substrate, the difference between the melting point of the low-temperature solder and the melting point of the solder is approximately The temperature is 200 to 400 ° C, preferably 250 to 3600 ° C.

According to the present invention, the present invention relates to a composition comprising 10 to 30% by weight of Cu,
A brazing material for power module joining, comprising an Ag-based alloy containing one or two of Sn and In in total of 20 to 40%.

The most preferable metal bonding materials which give the above-mentioned difference in melting point of 200 to 400 ° C. are as follows. That is,
AgCuSn based, Pb-based or Sn-based solder whose melting point is in the range of 180-330 ° C. and the melting point of the low-temperature brazing material is in the range of 500-600 ° C.
It is composed of a SnIn-based or AgCuSnIn-based Ag-based alloy material. Specifically, for example, 50% Ag-20% C
The melting point of the low-temperature brazing material of the Ag-based alloy composed of u-30% Sn was 515 ° C. Similarly, AgCu having a melting point of 580 ° C.
An In-based low-temperature brazing material was easily obtained. These low-temperature brazing materials are arranged at the joining portion in a pre-sintered preform or a paste state to be printed, and are joined by heating to a temperature higher than the melting point in a vacuum, an inert atmosphere, or a reducing atmosphere. The bonding strength at this time was a sufficiently high value of several tens MPa or more. The low temperature of the low-temperature brazing material means that the melting point of the low-temperature brazing material is sufficiently lower than that of a well-known silver brazing or active brazing material.

By combining these metal bonding materials, it is possible to realize a power module with small bonding deformation, high bonding yield, and high reliability of the bonding portion.

Further, the present invention provides a composite substrate having a ceramic substrate provided with a circuit board on one surface and a radiator plate on the other surface, and a heat sink substrate bonded to the radiator plate. Is 500 to 600 ° C.
g-Cu-Sn system, Ag-Cu-In system and Ag-Cu
-The bonding is performed by any of Sn-In based Ag-based alloys, and the bonding is performed by Cu10 to 30 by weight.
%, And a total of 20 to 40% of one or two of Sn and In
The heat sink substrate is made of a composite material mainly composed of copper and copper oxide, and the bonding is performed by using an A-based alloy having a melting point of 500 to 600 ° C.
It is characterized by being performed by a g-base alloy.

[0017]

(Embodiment 1) FIG. 1 shows an embodiment of a power module according to the present invention. As shown in the figure, the ceramic substrate 2 is provided with a heat sink 4 on one surface and circuit boards 3a and 3b on the other surface.
Here, the ceramic substrate 2 is made of alumina, aluminum nitride, silicon nitride, etc., and the heat sink 4 and the circuit boards 3a, 3b
Is made of any of copper, copper alloy, aluminum, and aluminum alloy. First, the heat sink 4 and the heat sink substrate 1 have a melting point of 515.
It is joined with low-temperature brazing material 5 at ℃. Next, the semiconductor power elements 7a and 7b are joined to the circuit boards 3a and 3b using solders 6a and 6b having a melting point of 180 ° C., respectively. It should be noted that Ni (nickel) having a thickness of several μm to 10 μm is provided on the bonding side of the semiconductor power elements 7a and 7b of the circuit boards 3a and 3b, the bonding side of the heat sink substrate 1 of the heat sink 4, and both surfaces of the heat sink substrate 1. Although plated, it is omitted from the drawing. The radiator plate 4 and the circuit boards 3a and 3b are directly joined to the ceramic substrate 2 by plating or the like. The radiator plate 4 is formed by plating simultaneously with the circuit boards 3a and 3b.

The heat sink substrate 1 is made of copper or copper alloy,
It is composed of aluminum, aluminum alloy, or copper composite. Copper composites are made of copper (Cu) and copper (I) oxide (Cu).
₂ O) in an alloy containing dispersed by dispersion ratio of the copper and the first copper oxide, a material that can control the thermal expansion coefficient and thermal conductivity. That is, by utilizing the high thermal conductivity of copper and the low thermal expansion of copper (I) oxide, a material suitable as a heat sink material having low thermal expansion and high thermal conductivity can be obtained. In particular,
A sintered material in which particles of 50% by weight of copper (Cu) and 50% by weight of cuprous oxide (Cu ₂ O) are dispersed, or a plastically processed alloy thereof is preferable.

The low-temperature brazing material 5 is composed of Ag 50% by weight, Cu
An Ag-based alloy having 20% and 30% Sn. solder
For 6a and 6b, an alloy composed of Sn 37% by weight and the balance Pb was used.

The semiconductor power elements 7a and 7b are connected to the circuit boards 3a and 3b.
Since the first low-temperature solder joint is not damaged at all during the second solder joining, a power module having a high joining yield and a highly reliable joint can be realized.

FIG. 2 is a plan view of the power module of FIG. The following description will be made on the assumption that all the elements having the same numbers described later have the same functions. The previous figure shows a XX section of this figure. This power module is covered with a resin case (not shown in the figure), and then attached to a cooling member (also not shown in the figure) using a plurality of mounting holes 13. used.

In this embodiment, the ceramic substrate 2 provided with the circuit boards 3a and 3b and the heat radiating plate 4 and the heat sink substrate 1 joined to the heat radiating plate 4 have a melting point of 500-6.
It is performed by using an Ag-based alloy of any one of Ag-Cu-Sn-based, Ag-Cu-In-based and Ag-Cu-Sn-In-based at 00 ° C.
0% and a total of 20 to 40 of one or two of Sn and In
%, Which is performed by an Ag-based alloy containing
The heat sink substrate 1 is made of a composite material mainly composed of the aforementioned copper and copper oxide, and is made of an integrated composite substrate joined by an Ag-based alloy having a melting point of 500 to 600 ° C. (Embodiment 2) This embodiment is different from FIG. 1 in that a thickness of 0.05 to 0.2 mm and Si
% Or less, using a substrate clad with an Al-based alloy plate containing
A heat sink substrate similar to that of Example 1 was joined to a Cu circuit board with Ni plating on one surface and a low-temperature brazing material having a low melting point, respectively, as in Example 1. The Al-based alloy plate on the heat sink substrate has a function as a heat sink.

Also in this embodiment, as in the first embodiment, the first low-temperature solder joint is not damaged at all during the second soldering for joining the semiconductor power element to the circuit board, so that the yield of joining is low. And a power module with high reliability and high reliability of the joint can be realized. (Embodiment 3) FIG. 3 is a sectional view showing another embodiment of the power module according to the present invention. FIG. 3 differs from the one shown in FIG. That is, the semiconductor power element 7a
And 7b are joined to the circuit boards 3a and 3b using the low-temperature brazing materials 9a and 9b described in Example 1 having a high melting point, respectively. Next, as in the first embodiment, the heat sink 4 and the heat sink substrate 1 are joined with solder 8 having a low melting point. Also in the case of this drawing, the first low-temperature solder joint is not damaged at all during the second solder joining, so that a power module with a high joining yield and high reliability of the joint can be realized. (Embodiment 4) FIGS. 4 and 5 are sectional views showing another embodiment of the power module according to the present invention. These embodiments are directed to a heat sink substrate of the power module shown in FIG.
1 is a power module in which a groove 10 is machined to form a cooling fin 11 for water cooling (FIG. 4), and a power module in which a water channel 12 is formed (FIG. 5). Thus, the heat sink substrate 1 has a large size and a large heat capacity structure. Even if the production speed is increased without paying much attention to the temperature distribution of the power module at the time of joining, a power module having a high joining yield and a highly reliable joint can be obtained.

Similarly, in the heat sink substrate of the power module shown in FIG. 3, the use of a cooling body provided with cooling fins and water passages can further improve the cooling efficiency.

Also in this embodiment, a substrate in which an Al-based alloy plate is clad on both surfaces of the ceramic substrate described in Embodiment 2 is used, and a Cu circuit board plated with Ni on one surface and a heat sink substrate on the other surface are respectively provided. A material joined by using a low-temperature brazing material having a melting point can be used, and the same effect can be obtained.

[0026]

According to the present invention, it is possible to realize a power module having small joint deformation, high joint yield, and high reliability. Such a power module is used as an IGBT module in a vehicle-mounted board computer and is suitable for a hybrid vehicle.

[Brief description of the drawings]

FIG. 1 is a sectional view of a power module according to the present invention.

FIG. 2 is a plan view of the power module of FIG.

FIG. 3 is a sectional view showing another embodiment of the power module according to the present invention.

FIG. 4 is a sectional view showing another embodiment of the power module according to the present invention.

FIG. 5 is a sectional view showing another embodiment of the power module according to the present invention.

[Explanation of symbols]

1: heat sink substrate, 2: ceramic substrate, 3a, 3
b: circuit board, 4: heat sink, 5: low-temperature brazing material, 6a, 6b,
8: solder, 7a: semiconductor power element, 7b: semiconductor power element, 9a, 9b: low-temperature brazing material, 10: groove, 11: cooling fin,
12 ... water channel, 13 ... mounting hole.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Teruyoshi Abe 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Yasuo Kondo 7, Omikacho, Hitachi City, Ibaraki Prefecture No. 1-1 Inside Hitachi, Ltd.Hitachi Laboratory (72) Inventor Noriyuki Watanabe 1-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Laboratory (72) Inventor Takashi Suzumura Tsuchiura, Ibaraki Prefecture 3550 Kida Yomachi Ichichi Hitachi Cable, Ltd. Tsuchiura Plant (72) Inventor Kazuhiko Nakagawa 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Tsuchiura Plant F-term (reference) 5F036 AA01 BA23 BB01 BC06

Claims (11)

[Claims] 1. A ceramic substrate having a circuit board on one surface and a radiator plate on the other surface, and a metal bonding material A on the radiator plate.
In a power module having a heat sink substrate joined by a bonding method and a semiconductor power element joined to the circuit board by a metal joining material B, one of the metal joining materials A and B has a melting point of 500 to 600. ° C
Ag-Cu-Sn-based, Ag-Cu-In-based and A
A power module comprising any one of g-Cu-Sn-In-based Ag-based alloys and the other being solder. 2. A ceramic substrate provided with a circuit board on one surface and a heat sink on the other surface, and a metal bonding material A on the heat sink.
In a power module having a heat sink substrate joined by a bonding method and a semiconductor power element joined to the circuit board by a metal joining material B, one of the metal joining materials A and B has a weight of Cu10 to 30. %
And a Ag-based alloy containing one or two of Sn and In and a total of 20 to 40%, and the other is made of solder. 3. A ceramic substrate provided with a circuit board on one surface and a heat sink on the other surface, and a metal bonding material A on the heat sink.
In a power module having a heat sink substrate joined by the above and a semiconductor power element joined to the circuit board by a metal joining material B, the heat sink substrate is made of a composite material mainly composed of copper and copper oxide, and One of the joining materials A and B has a melting point of 500 to 6.
A power module comprising an Ag-based alloy having a temperature of 00 ° C. and the other being a solder. 4. The method according to claim 1, wherein
The melting point of the g-base alloy is 200 to 400 ° C. higher than the melting point of the solder.
Power module characterized by its high cost. 5. The power module according to claim 1, wherein the solder is a Pb-based alloy or a Sn-based alloy having a melting point of 180 to 330 ° C. 6. The power module according to claim 1, wherein the heat sink substrate is formed of a cooling fin or a cooling body having a water passage formed therein. 7. A power module according to claim 1, wherein said ceramics substrate comprises an alumina substrate or an aluminum nitride substrate. 8. A composite substrate having a ceramic substrate provided with a circuit board on one surface and a radiator plate on the other surface, and a heat sink substrate bonded to the radiator plate, wherein the bonding has a melting point of 500 to 600. Ag-Cu-Sn
A composite substrate characterized by being made of any one of an Ag-based alloy, an Ag-Cu-In-based alloy, and an Ag-Cu-Sn-In-based alloy. 9. A composite substrate comprising a ceramic substrate provided with a circuit board on one surface and a radiator plate on the other surface, and a heat sink substrate bonded to the radiator plate, wherein the bonding is made by weight of Cu10. A composite substrate made of an Ag-based alloy containing 30% and one or two of Sn and In in total of 20 to 40%. 10. A composite substrate comprising a ceramic substrate provided with a circuit board on one surface and a radiator plate on the other surface, and a heat sink substrate joined to the radiator plate, wherein the heat sink substrate is made of copper, copper oxide and Wherein the bonding is performed by using an Ag-based alloy having a melting point of 500 to 600 ° C. 11. A power module joining brazing material comprising an Ag-based alloy containing 10 to 30% by weight of Cu and one or two of Sn and In in total of 20 to 40% by weight.