JP2001339020A - Semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor module of which cooling performance is improved by directly bringing a cooling fluid in contact with a semiconductor module substrate, and which is inexpensive and can meet a specification for cooling and fatigue durability by giving a controllability to the physical property of a heat radiating substrate. SOLUTION: This semiconductor module is provided with a plurality of semiconductor elements 102 joined with a heat radiating substrate 104 by means of an insulation substrate 103. The heat radiating substrate 104 is made of composite material of copper (Cu) and criprous oxide (Cu2O).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor module used for, for example, a power converter or a computer.

[0002]

2. Description of the Related Art A conventional semiconductor module has a composite layer and a metal layer in a thickness direction, as described in, for example, Japanese Patent Application Laid-Open No. 10-150124. It consists of a matrix in which a low thermal expansion fibrous or particulate dispersion material is dispersed, the metal layer is made of the same metal as the metal matrix of the composite layer, and the metal of the metal layer and the metal matrix of the composite layer are continuous. It is known that the outer surface side of the composite layer is a mounting portion for a heat-generating semiconductor device or a low thermal expansion substrate on which the heat-generating semiconductor device is mounted.

[0003]

According to such a semiconductor module, no consideration has been given to improving the cooling performance. In such a semiconductor module, an example in which fins are formed in a metal layer portion to improve cooling performance is disclosed, but copper (C) is used as a material of the metal layer portion.
u) and aluminum (Al) are suitable. However, although Cu has a high thermal conductivity, it has a problem in machinability, and for example, it is very difficult to machine flat fins having an aspect ratio of 5 or more in parallel. A
Although l is more excellent in workability than Cu, it has a problem that the cooling performance is inferior to Cu since the thermal conductivity is about の of that of copper.

[0004] In view of the above problems, an object of the present invention is to provide an excellent cooling performance while maintaining the thermal fatigue life of a module joint,
Another object of the present invention is to obtain a semiconductor module that can be manufactured at low cost.

[0005]

SUMMARY OF THE INVENTION The above objects are achieved by a semiconductor module in which a plurality of semiconductor elements are bonded to the heat radiation substrate through an insulating substrate, a first copper oxide material of the heat radiation substrate and the copper (Cu) (Cu ₂ O) is achieved by using a composite material.

Another object of the present invention is to provide a semiconductor module in which a plurality of semiconductor elements are joined to a heat radiating substrate via an insulating substrate, wherein the material of the heat radiating substrate is copper (Cu) or copper (Cu) oxide (Cu).
A composite of ₂ O), copper from the element mounting surface of the radiating board toward the fin side (Cu) and the first oxide (Cu ₂ O) stepwise varied first copper oxide compounding ratio of (Cu _This is achieved by reducing the content of 2O).

Another object of the present invention is to provide a semiconductor module in which a plurality of semiconductor elements are joined to a radiating substrate via an insulating substrate, wherein the material of the radiating substrate is copper (Cu) and copper (Cu) oxide.
_This is achieved by forming a composite material of 2O) so that the crystal grains of cuprous oxide (Cu ₂ O) are rod-shaped and substantially perpendicular to the element mounting surface of the heat dissipation substrate.

Another object of the present invention is to provide a semiconductor module in which a plurality of semiconductor elements are joined to a heat radiating substrate, wherein the heat radiating substrate is made of a composite material of copper (Cu) and cuprous oxide (Cu ₂ O). This is achieved by forming an insulating layer made of only cuprous oxide (Cu ₂ O) so as to be parallel to the element mounting surface.

[0009] The above-mentioned solution can further improve the effect by forming radiating fins on the side opposite to the element mounting surface of the radiating substrate or by forming a flow path for flowing a cooling fluid inside the radiating substrate. Can be obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, referring to FIGS.
A first embodiment of the semiconductor module of the present invention will be described.
Here, a liquid-cooled power semiconductor module for a power conversion device and a mounting and cooling structure thereof are shown, FIG. 1 is a configuration diagram showing a semiconductor module and a mounting and cooling structure thereof, and FIG. , FIG. 3 shows B in FIG.
FIG. 4 is a cross-sectional view taken along line CC in FIG. 2. The present embodiment shows a power converter for a hybrid vehicle, and shows an example in which two independent inverter circuits are mounted to control two rotating electric machines. In these drawings, a semiconductor module and a heat sink for cooling the semiconductor module are mainly shown, and other electric components such as a capacitor and a microcomputer control circuit, wiring, and the like are omitted.

First, the configuration of the present embodiment will be described. In the semiconductor module 101, an insulating substrate 103 is attached to a back surface of a semiconductor element 102, and a heat radiation substrate 104 made of a composite material of copper (Cu) and cuprous oxide (Cu ₂ O) is provided on the back surface of the insulating substrate 103. Metals such as solder are mainly used for joining these components.
A plurality of holes for fastening bolts are provided in the frame portion of the heat radiating substrate 104, and the semiconductor module 101 and the heat sink 1 are fastened by inserting bolts 106 into the holes via a seal described later.

The radiating substrate 104 is provided with radiating fins 105 for increasing the contact area with the cooling liquid and improving the cooling capacity so as to be parallel to the flow direction of the cooling liquid. Further, an electrode 107 used for connecting the semiconductor module 101 to another electric component is provided on the side facing the heat dissipation surface of the heat dissipation board. In this drawing, wiring between the internal semiconductor element and this electrode is omitted.

The heat sink 1 has two of the above-described semiconductor modules 101 mounted thereon, and each module constitutes a main circuit of an independent inverter circuit. Note that such a configuration is also applied to a case where one large-capacity rotating electric machine is controlled, for example, and a case where two modules constitute one inverter main circuit. Although not shown, other electric components such as a capacitor are mounted on the heat sink.

The heat sink 1 includes a semiconductor module 1
A cooling flow path 2 for passing a cooling liquid for cooling the cooling fluid 01 is formed inside, and an inlet 3a and an outlet 3b for introducing and discharging the cooling liquid from outside the heat sink are provided at both ends of the flow path. Have been. At this time, part of the cooling channel
The opening 5 is provided so that the cooling liquid directly contacts the heat dissipation board 104 and the heat dissipation fins 105 of the semiconductor module 101. This opening is formed to be smaller than the outer size of the heat radiating substrate in order to close the cooling channel by mounting the heat radiating substrate 104 on the opening 5. Further, outside the opening, the semiconductor module 10
A plurality of bolt holes 8 for mounting 1 are arranged so as to surround the opening.

Further, a groove 6 is provided in an annular area between the opening 5 of the cooling channel and the bolt hole 8 so as to allow the coolant to flow, and is formed in parallel with the cooling channel of the groove. A plurality of holes 7 are discretely provided on the bottom surface of the portion where the groove is formed to communicate with the bottom surface of the heat sink 1 from the bottom surface of the groove. The contact region between the semiconductor module 101 and the heat sink 1 by the groove 6 is divided into two regions: a region sandwiched between the opening 5 and the inner periphery of the groove 6 and a region sandwiched from the outer periphery of the groove to the outer periphery of the heat dissipation board of the semiconductor module. It is divided and formed. For the two annular contact areas, the semiconductor module 10
A seal for maintaining the liquid tightness of the heat sink 1 and the heat sink 1 is inserted between the mounting surface of the semiconductor module and the heat sink 1.

According to the sealing method described above, even if the coolant leaks to the outside of the first seal portion 9 due to the deterioration of the durability of the first seal portion or the decrease in the pressing force due to the loosening of the bolt, the coolant is discharged to the liquid discharge groove 6. In addition, the high-voltage electrical components discharged to the outside of the heat sink through the liquid discharge holes 7 and mounted on the semiconductor module mounting surface side are prevented from being wetted and causing insulation failure.

Next, as an operation and effect of the present invention, cooling of a semiconductor element will be described. A conventional power semiconductor module is cooled by attaching it to a heat sink via a member such as a heat conductive grease or a heat conductive sheet on the back surface of the heat radiating board. The conductivity is at most a few W /
(mK). On the other hand, the semiconductor element 102 according to the present embodiment is solder-bonded to the finned heat-radiating substrate 104 via the insulating substrate 103, and the thermal conductivity of the solder at this time is on the order of several tens of W / (m · K). Therefore, by employing this embodiment, the cooling capacity can be significantly improved.

Further, the heat dissipating substrate with fins is composed of a composite material of copper (Cu) and copper (I) oxide (Cu ₂ O), and contains copper (I) in an appropriate volume fraction with respect to copper. It is possible to realize a mounting structure that satisfies both the cooling performance required for the power conversion device and the fatigue life of the solder joint between the semiconductor element and the insulating substrate.

[0019]

[Table 1]

Table 1 shows the coefficient of linear expansion and the thermal conductivity at a typical compounding ratio of copper (Cu) and copper (I) oxide (Cu ₂ O) used in the present invention.

The linear expansion coefficients of Si and GaAs, which are typical examples of semiconductor device materials, are from 2.6 × 10 ^{-6 to} 3.
6 × 10 ⁻⁶ / ° C., 5.7 × 10 ^{−6 to} 6.9 × 10 ⁻⁶ / ° C., and AlN and Al ₂ which are typical examples of the material of the insulating substrate.
O _{3 has} a coefficient of linear expansion of about 5 × 10 ⁻⁶ / ° C. On the other hand, the coefficient of linear expansion of Cu and Al, which are conventional heat dissipation board materials, is 17 × 10 ⁻⁶ to 23 × 10 ⁻⁶ / ° C. Therefore, the difference in linear expansion coefficient between the heat dissipation substrate and the semiconductor element and the insulating substrate is large, and this difference causes distortion in the solder joining the above-mentioned members, and as a result, cracks and peeling occur in the solder, resulting in the semiconductor module. The heat radiation was significantly reduced.

On the other hand, in consideration of the cooling performance and durability required for the semiconductor module, the composition is appropriately selected from Table 1 and used as a heat-radiating substrate. Since it can be made smaller than a heat-dissipating substrate made of a single metal, the difference in linear expansion coefficient between an insulating substrate and a semiconductor element soldered on the heat-dissipating substrate can be reduced, resulting in cracks and peeling of the solder. It is possible to have a hard and long life structure. Further, in the composition shown in Table 1, the Vickers hardness of cuprous oxide (Cu ₂ O) was 3
By controlling the ratio to be equal to or less than 00, the machinability at the time of forming the fin on the heat dissipation substrate is improved, and the fin having a high aspect ratio can be processed in a short time.

Further, regarding the material composition of the heat dissipation board 104, the mixing ratio of copper (Cu) and copper oxide (Cu ₂ O) is changed stepwise from the element mounting surface side to the fin side to change the material ratio of copper oxide (Cu ₂ O). By lowering the content of Cu ₂ O), the coefficient of linear expansion is kept low near the element mounting surface to reduce the difference in the coefficient of linear expansion between the semiconductor element and the insulating substrate, and the heat conductivity is reduced near the heat radiating surface. A configuration that increases the heat dissipation is realized,
A mounting structure that satisfies both the cooling performance and the fatigue life of the solder joint can be realized.

Further, the material structure of the heat dissipation substrate 104 is such that the crystal grains of cuprous oxide (Cu ₂ O) are formed in a rod shape and substantially perpendicular to the element mounting surface of the heat dissipation substrate. The coefficient of linear expansion is reduced in the direction parallel to the mounting surface, that is, the deformation direction that generates thermal stress in the solder part, and the thermal conductivity is increased in the direction perpendicular to the element mounting surface, that is, the direction that determines the main heat dissipation. And a mounting structure that satisfies both the cooling performance and the fatigue life of the solder joint is realized.

Next, a second embodiment of the semiconductor module of the present invention will be described with reference to FIG. Here, an air-cooled power semiconductor module for a power converter and a mounted cooling structure thereof are shown. Even in the case of the air-cooled type, dust mixed with the cooling fluid may cause the housing 108 in which the module is mounted.
It is necessary to provide the seal 10 so as not to enter the inside of the device. Since the heat transfer rate of air cooling is smaller than that of liquid cooling, the aspect ratio of the fin needs to be even larger than that of liquid cooling in order to achieve the same cooling capacity as liquid cooling. However, as described above, the heat dissipation substrate is made of copper (C
By comprising a composite material of u) and cuprous oxide (Cu ₂ O), the machinability at the time of forming the fin is improved, and the fin having a high aspect ratio can be processed in a short time.

Next, a third embodiment of the semiconductor module of the present invention will be described with reference to FIG. Here, an air-cooled power semiconductor module for a power converter and a mounted cooling structure thereof are shown.

Regarding the material composition of the heat radiation substrate 104 in this embodiment, the surface of the element mounting surface has copper oxide (Cu).
The ₂ O) only the insulating layer 104a is formed in place, a semiconductor element 102 was directly bonded on the insulating layer 104a.
This makes it possible to omit the conventionally used insulating substrate and to realize a configuration in which the coefficient of linear expansion near the element mounting surface is kept low, so that a semiconductor module with low cost and high reliability can be obtained.

Next, a fourth embodiment of the semiconductor module of the present invention will be described with reference to FIG. Here, a liquid-cooled power semiconductor module for a power converter and a mounted cooling structure thereof are shown.

In this embodiment, a number of cooling channels are formed inside the heat dissipation substrate 104. That is, the heat sink 1 and the heat dissipation board 104 shown in the first embodiment are integrated. In this case, no sealing portion is required between the heat sink and the heat radiating substrate, so that a structure that does not essentially leak water is provided, and the reliability of the device is improved.

In the above embodiments, an example in which a composite material of copper (Cu) and copper (I) oxide (Cu ₂ O) is applied to the function as a heat dissipation board has been described. In some cases, it has both the role of a heat dissipation board and the role of an electrode. Since the present invention uses copper having excellent conductivity as a basic component, the same effect as that of the above-described embodiment can be obtained even when the present invention is applied to such a function of an electrode and a heat dissipation substrate.

[0031]

According to the semiconductor module of the present invention, the cooling fluid can be brought into direct contact with the heat radiating substrate which is a component of the semiconductor module, and at the same time, the linear expansion coefficient and the thermal conductivity of the semiconductor module can be controlled. Control of the heat dissipation board according to the cooling and fatigue durability specifications of the semiconductor module, thereby simultaneously improving both the cooling performance of the semiconductor module and the fatigue life of the solder joint at low cost. Can be done.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a semiconductor module cooling unit according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA 'in FIG.

FIG. 3 is a sectional view taken along the line BB ′ in FIG. 2;

FIG. 4 is a sectional view taken along the line CC ′ in FIG. 2;

FIG. 5 is a configuration diagram of a semiconductor module cooling unit according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a semiconductor module cooling unit according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram of a semiconductor module cooling unit according to a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat sink, 2 ... Cooling channel, 3a ... Coolant inlet,
3b: Coolant outlet, 4: Cooling channel side wall, 5: Cooling channel opening, 6: Liquid discharge groove, 7: Liquid discharge hole, 8: Bolt hole, 9
... first seal, 10 ... second seal, 11 ... water leak sensor,
12 ... heat sink cover, 13 ... spacer, 14 ...
Disturbance promoter, 101: power module, 102: semiconductor element, 103: insulating substrate, 104: heat dissipation substrate, 104
a: insulating layer in the heat dissipation board, 105: heat dissipation fin, 106 ...
Bolt, 107: electrode, 108: housing.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazutaka Okamoto 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Research Laboratory Co., Ltd. F-term in the Automotive Equipment Group of Hitachi, Ltd. (Reference) 5F036 AA01 BA05 BB01 BD00 BD01 BD13

Claims (1)

[Claims] 1. A semiconductor module in which a plurality of semiconductor elements are joined to a heat radiating substrate via an insulating substrate, wherein the material of the heat radiating substrate is made of a composite material of copper (Cu) and cuprous oxide (Cu ₂ O). A semiconductor module characterized by the above-mentioned.