JPH10173109A - Power semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel power semiconductor module having a high- reliability head sink which ensures a high thermal conductivity and small thermal expansion difference from an insulation board. SOLUTION: The semiconductor power module includes an insulation board which mounts semiconductor chips and electrodes and is mounted on a heat sink and has such a structure that all the components on the heat sink are sealed such as IGBT. The heat sink comprises Cu or Cu alloy high-thermal conductivity layers 3 and Fe-Ni alloy low-thermal expansion layers 1 alternately laminated amounting to 10 or more layers, pref. 50 or more layers to form a multilayer structure. The high-thermal conduction layers 3 at both sides of each low-thermal expansion layer 1 are connected through through-holes of this layer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power semiconductor module used for a motor drive and the like.

[0002]

2. Description of the Related Art A power semiconductor module includes a power supply semiconductor chip such as an IGBT element and an insulating substrate on which a plurality of collector, emitter and gate electrodes are mounted by soldering or soldering. The structure on the heatsink is sealed with resin and covered with a case made of resin or the like. In recent years, power semiconductor modules mounted with IGBT elements and the like have been used instead of GTO thyristors. These power semiconductor modules are required to have a characteristic of switching a high voltage and a large current at a high speed. As described above, a large current flows through the power semiconductor module,
Since switching is performed at high speed, a large amount of heat is generated.
This heat generation not only reduces the performance and life of the semiconductor chip, but also lowers the joining reliability of each part constituting the power semiconductor module. Therefore, a radiator plate is usually provided in the power semiconductor module.

An example of the structure of a power semiconductor module using a heat sink will be described with reference to FIG. An insulating substrate 9 made of ceramic such as alumina or aluminum nitride is arranged on the heat sink 8, and a plurality of power supply semiconductor chips such as IGBT elements and a plurality of collector, emitter and gate electrodes are mounted by brazing or soldering. Is done. Between the semiconductor chip 10 and the collector electrode 11,
For example, when the semiconductor chip 10 is made of silicon and the collector electrode 11 is made of Cu, a thermal stress buffer plate 14 is provided to alleviate the thermal stress caused by the high temperature during brazing,
They are joined together by brazing materials 17 and 18. Further, the collector electrode 11 and the insulating substrate 9 are joined by a brazing material 19. The emitter electrode 12 and the gate electrode 13 are also joined on the insulating substrate by brazing materials 16 and 20.
The emitter electrode 12 and the gate electrode 13 are connected to the semiconductor chip 1
In each of the regions 0, aluminum wires 21, 22 and the like are provided. The insulating substrate 9 on which the structure thus configured is mounted and the heat sink 8 are generally joined by a brazing material 15.

The structures on the heat sink 8 are covered with, for example, a resin cover 23. The bottom of the cover is substantial,
It becomes a heat sink. That is, the surface of the heat sink opposite to the insulating substrate is not covered with the cover. External electrode terminals 24 and 2 are provided on the cover.
5 and 26 and a control signal terminal 27 are provided, and are respectively wired to predetermined electrodes on the insulating substrate and inside the cover. The resin 28 is injected into the space surrounded by the cover and the heat radiating plate in order to protect the above-mentioned mounted components (semiconductor chips, electrodes, etc.) and various wirings on the insulating substrate. At this time, gel-like silicon or the like may be used instead of the resin. Further, the heat sink may be provided with mounting holes 29 and 30 as necessary.

At present, ceramics such as alumina or aluminum nitride are used for the insulating substrate of the power semiconductor module as described above. Therefore, the heat sink is
It is known that it is preferable to use a high thermal conductive material which has a small difference in thermal expansion from these ceramic insulating substrates and has excellent heat dissipation in order to maintain the bonding reliability with the insulating substrate. Therefore, in the past, only high thermal conductivity was considered,
Although a heat radiating plate made of a simple copper plate has been used, an expensive Mo plate or a composite material of Cu and W is used in some parts in order to ensure high thermal conductivity and low thermal expansion.

Furthermore, as a high thermal conductive and low expansion material replacing the Mo plate, Japanese Patent Publication No. 7-80272 discloses a copper or copper alloy plate rolled and integrated on both sides of a low thermal expansion metal plate having a through hole in the thickness direction. There has been proposed a composite material for a heat spreader having a five-phase structure in which copper or a copper alloy is further exposed and a copper or copper alloy plate is further rolled thereon. The heat spreader having this structure can ensure high thermal conductivity in the stacking direction, which cannot be obtained by a simple laminate, by using copper or a copper alloy filled in the through-hole portion, and is excellent in heat dissipation characteristics. Also, for example, Toshiba Technical Publication Vol. 13
As described in -85, an attempt has been made to arrange a low thermal expansion material in a lattice or mesh on the bonding surface side of a heat sink and an insulating substrate to achieve both low thermal expansion characteristics and high thermal conduction characteristics. Is

[0007]

When a heat radiating plate made of a simple copper plate is used, since the thermal expansion difference between the above-mentioned ceramic insulating substrate and the copper plate is large, the heat radiating plate warps after heating by brazing or soldering. (Adhesion in a state where the joint surface side with the insulating substrate expands) occurs. When such a power semiconductor module is mounted and used on a motor drive device or the like, a gap is generated in the mounting portion due to the warp of the heat radiating plate, thereby lowering the thermal conductivity and lowering the heat radiation of the entire power semiconductor module. In addition, due to the temperature change during the operation of the power semiconductor module, thermal fatigue occurs in the solder or solder at the joint between the insulating substrate and the heat sink due to the difference in thermal expansion, and the joining reliability is significantly reduced.

On the other hand, the above-mentioned Toshiba Technical Publication Vol. 1
The heat dissipation plate described in 3-85 is a ceramic insulation substrate in which a low thermal expansion material (42 alloy or molybdenum) is arranged in a lattice or mesh on the bonding surface side or both surfaces of the copper heat dissipation plate with the insulating substrate. In this case, the difference between the thermal expansion characteristics and the thermal expansion characteristics is reduced. However, according to the study of the present inventors, the Toshiba Technical Publication Vol. In the heat sink described in 13-85, the thickness of the low thermal expansion layer is at most 20% of the entire thickness of the heat sink, and the heat from the insulating substrate side end surface does not uniformly suppress the expansion of the heat sink, and warp. Is likely to occur.

Further, since the heat sink having the above structure uses brazing or soldering as a joining method of the low thermal expansion material and the copper heat sink, the problem of thermal fatigue of the brazing or solder at the joining interface is newly added. In some cases, and was still insufficient as a heat sink for power semiconductor modules. Further, when the Mo plate is used as a heat radiating plate, the difference in thermal expansion from the insulating substrate is suppressed, but the thermal conductivity is lower than that of copper, and there is a problem in heat radiation. Further, the Mo plate is expensive, which increases the cost of the power semiconductor module as a whole.

According to the study of the present inventors, a copper or copper alloy plate is rolled and integrated on both surfaces of a low thermal expansion metal plate having through holes in the thickness direction described in Japanese Patent Publication No. 7-80272. The material has a structure of at most five layers, and there is a problem that the end face is likely to be warped due to a difference in thermal expansion characteristics of each layer. Further, the manufacturing method described in Japanese Patent Publication No. 7-80272 discloses that By cold rolling,
Even if diffusion annealing is applied after lamination, the diffusion layer formed between the layers is thin, and a part of the unbonded portion may be generated, which is not necessarily excellent in terms of bonding reliability. The present invention has been made in view of the above-described problems, and has an object to provide a new power semiconductor module including a highly reliable heat radiating plate that can ensure high thermal conductivity and has a small difference in thermal expansion from an insulating substrate. And

[0011]

Means for Solving the Problems The present inventors have studied to prevent a difference in thermal expansion characteristics between an insulating substrate and a heat radiating plate in a power semiconductor module. Then, by employing a method of hot pressure bonding, the Fe-Ni-based alloy layer having a plurality of through holes and a copper or copper alloy layer are combined to form a multilayer structure of 10 or more layers, It has been found that a structure in which a plurality of through holes are filled with the above-described copper or copper alloy layer can be obtained. The present inventors have found out that the multilayer structure having 10 or more layers can solve the problem of warpage and reduce the difference in thermal expansion characteristics between the insulating substrate and the present invention.

That is, the present invention provides a power semiconductor module having a structure in which an insulating substrate on which a plurality of semiconductor chips and a plurality of electrodes are mounted is mounted on a radiator plate, and a structure on the radiator plate is sealed. The heat sink has a high thermal conductive layer of copper or copper alloy and a low thermal expansion layer of Fe-Ni alloy alternately laminated, and has a multilayer structure of 10 or more layers,
The high thermal conductive layer sandwiching the low thermal expansion layer is a power semiconductor module continuous through a plurality of through holes formed in the low thermal expansion layer. The heat sink preferably has a multilayer structure of 50 or more layers.

The above-described heat radiating plate of the present invention comprises a thin plate made of, for example, copper or a copper alloy, and a Fe—Ni having a plurality of through holes formed therein.
After laminating the alloy thin plates alternately and filling the can body,
After reducing the pressure to less than minus the third power Torr, sealing is performed, and then 100 MPa in a temperature range of 700 to 1050 ° C.
A bonding process is performed by applying pressure as described above, and copper or a copper alloy is filled in the through-holes and diffusion-bonded, followed by hot rolling and cold rolling to finish to a predetermined thickness.

Preferably, the low thermal expansion layer has a thickness of 0.1
The power semiconductor module is provided with a heat radiating plate having a thickness of not more than 1 mm. Further, a continuous high heat conductive layer of copper or copper alloy is laminated on the outermost layer of the heat sink, or Fe-
It is desirable to laminate a continuous low thermal expansion layer of a Ni-based alloy.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One of the features of the present invention is that a heat radiating plate applied to a power semiconductor module has a multilayer structure of 10 layers or more, preferably 50 layers or more. An object of the present invention is to suppress deformation such as warpage of a heat radiating plate due to a difference in thermal expansion coefficient between a conductive layer and a low thermal expansion layer of an Fe-Ni alloy.

The present inventor has studied the heat sink applied to the power semiconductor module as shown in FIG. 4 in order to make the above-mentioned multi-layer structure of 10 or more layers into reality, and inserts a low thermal expansion layer. In order to make the high thermal conductive layer continuous through the plurality of through holes formed in the low thermal expansion layer, after lamination, the can is filled in a can body, and the pressure is reduced to 10 -3 Torr or less, and then sealed. In this temperature range, the bonding process is performed by applying a pressure of 50 MPa or more. Thus, the composite material having the high thermal conductive layer connected to the through-hole without applying the rolling compression bonding method, which has conventionally been limited to the five-layer structure, by performing the vacuum bonding and the heat bonding under the high pressure. Can be made into 10 layers or more at once.

In the present invention, the thickness of the low thermal expansion layer is preferably reduced to 0.1 mm or less. By forming such a thin, low-thermal-expansion layer in multiple layers, it is possible to more reliably suppress deformation such as warpage due to a difference in the coefficient of thermal expansion. Preferably, a continuous high thermal conductive layer of copper or a copper alloy is laminated on the outermost layer, or Fe-N
A continuous low thermal expansion layer of an i-based alloy is laminated. By forming a continuous high thermal conductive layer of copper or a copper alloy having no through hole in the outermost layer or a continuous low thermal expansion layer of an Fe-Ni-based alloy, non-uniformity of the surface during plating treatment is eliminated, and a favorable Plating property can be obtained. Whether the outermost layer is a high thermal conductive layer or a low thermal expansion layer can be arbitrarily selected depending on the required characteristics of the element to be radiated. For example, the outermost layer may be a low thermal expansion layer when low thermal expansion characteristics of the bonding surface are particularly required, and may be a high thermal expansion layer when high thermal conductivity characteristics are particularly required.

FIG. 1 shows a basic structure of a composite material serving as a radiator plate used in the present invention in which a high thermal conductive layer of copper or a copper alloy and a low thermal expansion layer of an Fe—Ni alloy having a plurality of through holes are laminated. As shown. FIG. 1 shows a portion where a low thermal expansion layer 1 and a high thermal conductive layer 3 of a composite material 5 having a multilayer structure are joined. As shown in FIG. 1, the high thermal conductive layers 3 on both sides of the low thermal expansion layer 1 are continuous with copper or a copper alloy filled in the through holes 2. An ideal cross section is shown on the right side of FIG. By doing so, F
This ensures heat transfer across the low thermal expansion layer of the e-Ni alloy. Further, as shown in FIG. 2, in the present invention, the outermost layer 4 of the composite material 5 is a continuous high heat conductive material of copper or copper alloy having no through-hole or Fe-free having through-hole.
It is possible to arrange a continuous low thermal expansion material of a Ni-based alloy.

In the present invention, in order to increase the bonding reliability between the low thermal expansion layer and the high thermal conductive layer, specifically, to obtain a sufficiently thick diffusion layer having a thickness of 10 μm or more, the thickness of the layer is set to 700 to 700 μm.
A pressure of 50 MPa or more is applied in a temperature range of 1050 ° C. When a high pressure of 50 MPa or more is applied, it is possible to form a diffusion layer having a thickness of 10 μm or more, which is significantly thicker than that formed by conventional cold rolling and compression bonding and annealing, in a temperature range of 700 to 1050 ° C. The pressure is preferably as high as possible,
From the viewpoint of device performance, 200 MPa or less is realistic, and is preferably in the range of 80 to 150 MPa. In the present invention, at a temperature of 700 ° C. or less, diffusion becomes insufficient and sufficient bonding strength cannot be obtained. At a temperature of 1050 ° C. or more, the surface oxidation of copper or a copper alloy becomes remarkable, and a sufficient bonding strength cannot be obtained, and the copper or the copper alloy may be dissolved, which is not preferable. Therefore, in the present invention,
The temperature range was defined as 700 to 1050 ° C.

Further, in the present invention, prior to the above-described bonding process, after filling in a can body, 10 minus 3 power To
A step of sealing after reducing the pressure to a value lower than rr is provided. In the present invention, if gas remains in the through-hole formed in the Fe-Ni-based alloy material, it becomes impossible to sufficiently fill the through-hole with copper or a copper alloy. Further, in the present invention, after the above-described joining processing, the sheet is finished to a predetermined thickness by hot rolling and cold rolling. In the present invention, the bonding treatment is performed under a high pressure, but it is difficult to sufficiently fill the through-hole with copper or a copper alloy by this alone. Thus, the present invention provides hot rolling and cold rolling after the joining process.
The cold rolling is performed to obtain cleanliness and flatness that can be used as a composite material for electronic components.

In the present invention, the first purpose of the low thermal expansion layer of the Fe—Ni alloy is to reduce the thermal expansion of the composite material of the present invention. Preferably,
The composite material should be 3 to approximate the coefficient of thermal expansion of the insulating substrate.
It is desirable to arrange so that the coefficient of thermal expansion at 0 ° C. to 300 ° C. is in the range of 4 to 11 × 10 −6 / ° C. As an Fe-Ni alloy specifically used, Fe
-42% Ni alloy, so-called invar alloy of Fe-36% Ni alloy, so-called super-invar alloy of Fe-31% Ni-5% Co alloy, Fe-29% Ni-17% C
o 30% to 60% of Ni such as alloy, with the balance being Fe or Ni
Can be used in which a part of is replaced by Co as a basic element.

It is also possible to include other additional elements. For Cr, 15% by weight or less, and elements of the 4A, 5A, and 6A groups according to various requirements such as thermal expansion characteristics and mechanical strength. It can be added as long as an austenite structure that does not impair the low thermal expansion characteristics can be maintained. For example,
Cr, which is effective for forming an oxide film, is 15% by weight or less, and Nb, T is 5% by weight or less as an element for improving strength.
i, Zr, W, Mo, Cu, 5% by weight or less of Si, Mn or 0.1% by weight as an element for improving hot workability
The following Ca, B, Mg can be used.

In the present invention, the high heat conductive layer of the heat sink applied to the power semiconductor module is defined as copper or a copper alloy. Pure copper is extremely excellent in terms of thermal conductivity and is effective as a heat sink for heat conduction, but it may be used for mechanical strength, solderability, silver brazing properties, heat resistance, etc. It is possible to add alloying elements to improve the properties accordingly. For example, Sn or Ni can be dissolved in copper or a copper alloy to improve mechanical strength. Also, when Ti is added in a composite with Ni, it precipitates as a compound of Ni and Ti in the copper matrix, and improves mechanical strength and heat resistance. Zr improves solder weather resistance. It is known that Al, Si, Mn, and Mg improve the adhesion to the resin. Since the purpose of the present invention is to impart heat dissipation to the copper or copper alloy layer, the above-mentioned additional element that reduces the heat dissipation is preferably 10% by weight or less.

[0024]

The present invention will be described below with reference to examples. As the material for the low thermal expansion layer of the heat sink used in the power semiconductor module of the present invention, Fe-42% Ni alloy, Fe-36%
Ni alloy, Fe-31% Ni-5% Co alloy and Fe
A -29% Ni-17% Co alloy was selected, and cold rolling and annealing were repeated to obtain a 0.2 mm-thick Fe-Ni-based alloy sheet. Through holes of 0.8 mm in diameter and 1.0 mm in pitch were formed in the entire surface of the thin plate by photoetching in the Fe-Ni-based alloy to obtain a material for a low thermal expansion layer shown in FIG. Pure copper (oxygen-free copper), Cu-2.4% Fe-0.07% P-0.12% as a material for the high thermal conductive layer
Zn alloy (Cu alloy A) and Cu-2.0% Sn-
0.2% Ni-0.04% P-0.15% Zn alloy (C
u alloy B) was selected to obtain a thin plate having a thickness of 0.35 mm. Each of these thin plates was slit to a width of 120 mm, and then cut to a length of 800 mm by a fixed-size cutting machine to obtain a material 7 for a high heat conductive layer shown in FIG. Note that Cu
The composition of the alloy is% by weight.

Next, these sheets were combined in the combination shown in Table 1 so that a high thermal conductive layer of copper or a copper alloy sandwiched a low thermal expansion layer of an Fe—Ni alloy in a 5 mm thick SC material case. The laminate was alternately laminated to obtain a laminate in which the outermost layer having 50 low thermal expansion layers and 51 high thermal conductive layers was a continuous high thermal conductive layer. Further, as another example, the same material as that of the low thermal expansion layer constituting the laminate, which is formed on the outside of the laminate structure A and has a thickness of 0.3 m, which does not form a through hole, is further provided.
m to obtain a laminate in which the outermost layer is a low thermal expansion layer having no through holes. (Referred to as laminated structure B)

Next, the case of the S10C material was hermetically sealed by welding after reducing the pressure to less than 10.sup.-3 Torr. The S10C case (hereinafter referred to as a can material) having the degassed laminate was joined and integrated by hot isostatic pressing at a temperature shown in Table 1 at 1,000 atm. The S10C case material on the upper and lower surfaces of the can material after the hot isostatic pressing was removed by grinding to obtain a material before hot rolling. 750-900 ° C
Hot rolling was performed in the above temperature range to obtain a plate having a thickness of 6 mm. The plate was further subjected to descaling by pickling, and then cold-rolled to obtain a final plate having a thickness of 4.5 mm. The thickness of each layer was about 45 μm.

Next, a cutting process is performed from this plate,
A radiator plate for a power semiconductor module having a size of × 100 (mm) was manufactured. Brazing with an alumina insulating substrate when manufacturing a power semiconductor module using the above heat sink
In the (heating at 830 ° C.) step, the heat sink has a warp of 40 μm.
m. On the other hand, for comparison, when a simple copper plate was used as the heat radiator plate of the same size, the warp of the heat radiator plate was as large as 300 μm, which was not preferable. The thermal characteristics of the radiator plate alone are as follows: the thermal conductivity is 120 W / m · K or more and the thermal expansion coefficient is 7 (× 10
(-6th power / ° C) or less was obtained. This is in good agreement with the coefficient of thermal expansion of the alumina insulating substrate. The thermal conductivity is measured by a laser flash method, and the coefficient of thermal expansion is a value obtained by measuring a value of α30 to 300 ° C. in a temperature range of 30 to 300 ° C. From the above characteristics, the power semiconductor module according to the present invention is excellent in heat dissipation, and even when the temperature changes during the operation of the power semiconductor module, the joining reliability between the insulating substrate and the heat-sink brazing portion can be made high. You can see that.

[0028]

[Table 1]

As shown in Table 1, the composite material for electronic parts of the present invention has a multilayer structure of more than 50 layers,
High thermal conductivity characteristics and low thermal expansion characteristics of 7 (× 10−6 / ° C.) or less could be obtained.

[0030]

As is clear from the above description, the present invention suppresses warping of the heat radiating plate by forming the heat radiating plate of the power semiconductor module into a multi-layer structure of 10 or more high thermal conductive layers and low thermal expansion layers. As a result, the heat dissipation of the power semiconductor module can be improved by eliminating the gap in the mounting portion. Further, it is possible to provide a power semiconductor module having excellent bonding reliability between the insulating substrate and the heat sink brazing portion.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a basic configuration of a composite material of the present invention.

FIG. 2 is a conceptual diagram showing a preferred example of an outermost layer of the composite material of the present invention.

FIG. 3 is a view for explaining a material of the composite material of the present invention.

FIG. 4 is a configuration example of a power semiconductor module to which the present invention is applied.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 low thermal expansion layer, 2 through hole, 3 high thermal conductive layer, 4 outermost layer, 5 composite material, 6 material for high thermal conductive layer, 7 material for low thermal expansion layer, 8 radiator plate, 9 insulating substrate, 10 semiconductor chip, 11 collector Electrode, 12 emitter electrode,
13 gate electrode, 14 thermal stress buffer, 15, 16,
17, 18, 19, 20 brazing material, 21, 22 Al
Wires, 23 covers, 24, 25, 26 external electrode terminals,
27 control signal terminal, 28 resin, 29, 30 mounting holes

Claims (4)

[Claims] 1. A semiconductor module having a structure in which an insulating substrate on which a plurality of semiconductor chips and a plurality of electrodes are mounted is mounted on a heat sink, and a structure on the heat sink is sealed. Or a copper alloy high thermal conductivity layer and F
The low thermal expansion layers of the e-Ni alloy are alternately laminated to form a multilayer structure of 10 or more layers, and the high thermal conductive layer sandwiching the low thermal expansion layer is continuous through a plurality of through holes formed in the low thermal expansion layer. A power semiconductor module, characterized in that: 2. The thickness of the low thermal expansion layer constituting the heat sink is as follows:
The power semiconductor module according to claim 1, wherein the power semiconductor module is 0.1 mm or less. 3. The power semiconductor module according to claim 1, wherein a continuous high heat conductive layer of copper or a copper alloy is formed on a surface of the heat sink facing the insulating substrate. 4. A surface of the heat sink opposite to the insulating substrate is provided with F
3. The power semiconductor module according to claim 1, wherein a continuous low thermal expansion layer of an e-Ni-based alloy is formed.