JP2003306730A - Al-SiC-BASED COMPOSITE AND HEAT-DISSIPATING COMPONENT - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Al-SiC-based composite which is capable of keeping gastightness of its inside by suppressing melting of metal containing aluminum as a main component when a DBA (direct brazing aluminum) substrate is joined by using an aluminum-based brazing material, sufficiently dissipating heat generated from semiconductor chips to the outside, and further preventing the generation of shrinkage cavities or cracks after the metal containing aluminum as the main component has been impregnated under pressure, and to provide a heat-dissipating component. <P>SOLUTION: The Al-SiC-based composite is obtained by impregnating the metal containing aluminum as the main component into a porous body mainly comprising silicon carbide, and the initial crystallization temperature of the metal containing aluminum as the main component is ≥615°C. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite of aluminum and silicon carbide (Al-) formed by impregnating a porous body mainly composed of silicon carbide (SiC) with a metal containing aluminum (Al) as a main component. SiC-based composite).
INDUSTRIAL APPLICABILITY The Al-SiC composite of the present invention has low thermal expansion and high thermal conductivity characteristics, and is suitable for a heat dissipation component used for a semiconductor device such as a heat dissipation substrate, a heat sink, a package.

[0002]

2. Description of the Related Art In recent years, in the field of industrial equipment, development of a high power module device for efficiently exchanging and controlling a large power to an optimum power by using a semiconductor switching device has been advanced. For example, high voltage as an inverter for electric vehicles,
There is an IGBT module capable of high current operation. The heat generated from the semiconductor chip is also increasing in accordance with such a high power module. The semiconductor chip is vulnerable to heat, and if the heat generation increases, malfunction or destruction of the semiconductor circuit will be caused. Therefore, a heat dissipation component such as a heat sink is provided on the back surface of a circuit board for mounting electronic components such as semiconductor chips, and the heat generated from the semiconductor chip is radiated to the outside through the heat dissipation component to stabilize the operation of the semiconductor circuit. Is being done. Circuit boards for mounting electronic components include silicon nitride (Si ₃ N ₄ ) and aluminum nitride (A
DBC (Dire) in which a copper (Cu) plate is brazed to a ceramic plate such as 1N) or aluminum oxide (Al ₂ O ₃ ).
ctBonding Cupper) substrate is mainly used.

Conventional materials for heat dissipation components include copper, molybdenum, and tungsten. The heat dissipation component made of molybdenum or tungsten is expensive, and since the specific gravity of metal is large, the weight of the heat dissipation component becomes heavy, which is not preferable for applications in which weight reduction of the heat dissipation component is desired.

Further, since the heat dissipation component made of copper has a large difference in coefficient of thermal expansion between the heat dissipation component and the DBC substrate joined to the heat dissipation component, the heat dissipation component and the DBC substrate may be heat-bonded to each other or due to a thermal cycle during use. Destruction of solder layer, blocking of heat flow path, D
The BC substrate is easily cracked. In other words, heat dissipation parts and DB
The C substrate is brazed with solder, and is heated to a temperature higher than the melting point of the brazing material and then cooled to room temperature. At that time, they are fixed to each other at the freezing point of the brazing material, and then the heat radiating component and the DBC board shrink according to their own coefficients of thermal expansion while they remain fixed, and thermal stress and thermal strain remain at their joints and warp etc. Causes deformation. When thermal stress is repeatedly applied during use of the module device and superposed on residual thermal stress and thermal strain, the thermal flow path is blocked due to fatigue failure of the solder layer and cracks in the mechanically brittle DBC substrate occur. Occurs.

As a material for heat dissipation parts replacing conventional materials such as copper, Al having low thermal expansion and high heat conduction characteristics in which silicon carbide is dispersed in aluminum or aluminum alloy.
-SiC-based composites are receiving attention (Japanese Patent Publication No. 7-261).
74, JP-A-64-83634 and the like). Al-S
As a method for producing the iC-based composite, a porous body (preform) formed of silicon carbide powder or silicon carbide fibers is used, the porous body is placed in a space in a mold, and an aluminum ingot is brought into contact with the nitrogen atmosphere. There is a molten metal impregnation method in which a porous body of silicon carbide is impregnated by pouring aluminum that has been heated and melted under pressure or without pressure into a space in a mold and then cooled. According to this manufacturing method, the content of silicon carbide can be selected within the range of 20 to 90% by volume. In addition, the silicon carbide porous body has a high degree of freedom in the shape, and has an advantage that a product having a complicated shape can be formed into a net shape.

On the other hand, in recent years, as a circuit board, a DBA (Direct Brazing Aluminum) board has been applied instead of the DBC board. The DBA substrate is a substrate obtained by brazing and wiring a ceramic plate to an aluminum plate with an aluminum-based brazing material. Since the plastic performance of aluminum is higher than that of copper, it is attracting attention as a circuit board having excellent durability and reliability.

[0007]

When joining the DBA substrate to the heat dissipation component, an aluminum brazing material is usually used. In the case of heat dissipation components made of conventional metals such as copper, molybdenum, and tungsten, the melting temperature of these heat dissipation components is much higher than the melting temperature of the aluminum-based brazing filler metal, so no problem occurs during joining.

On the other hand, the Al-SiC composite according to the present invention comprises an Al-SiC composite main body formed by impregnating a porous body mainly composed of silicon carbide with a metal containing aluminum as a main component, and an Al-SiC composite main body. It is composed of an aluminum coating layer formed on the surface of the SiC composite main body and made of a metal containing aluminum as a main component. In the case of a heat dissipation component made of this type of Al-SiC composite, if the primary crystal temperature of the metal whose main component is impregnated aluminum is lower than a predetermined temperature,
A when joining DBA substrates using aluminum brazing material
The metal containing aluminum as the main component, which constitutes the 1-SiC composite, is melted, and a part thereof is melted out to the surface of the Al-SiC composite. As a result, the density inside the Al-SiC-based composite decreases, and not only the airtightness is no longer maintained, but also the thermal conductivity, bending strength, and Young's modulus decrease.
As a result, the heat generated from the semiconductor chip is hindered from being radiated to the outside, which causes a problem that the semiconductor circuit malfunctions or is destroyed.

Further, when pure aluminum without addition of an alloy is used to raise the melting temperature, the difference between the primary crystal temperature and the solidus temperature of aluminum is small, so after aluminum is press-fitted and impregnated, Shrinkage cavities are likely to occur on the surface of the aluminum coating layer of the Al-SiC composite. Further, there is a problem that cracks are likely to occur at the boundary between the Al-SiC composite main body and the aluminum coating layer.

The present invention has been made in view of these circumstances, and suppresses melting of a metal containing aluminum as a main component at the time of joining a DBA substrate using an aluminum-based brazing material, thereby suppressing Al-SiC-based metal. The airtightness inside the composite can be maintained, the heat generated from the semiconductor chip can be sufficiently dissipated to the outside, and the shrinkage cavities and cracks after the metal containing aluminum as the main component is press-fitted and impregnated can be prevented. It is an object to provide an Al-SiC based composite and a heat dissipation component.

[0011]

The Al-SiC composite of the present invention is formed by impregnating a porous body mainly composed of silicon carbide with a metal containing aluminum as a main component.
The C-based composite is characterized in that the primary crystal temperature of the metal containing aluminum as a main component is 615 ° C. or higher.

In the present invention, the solidus temperature of the metal containing aluminum as a main component is preferably 560 ° C. or higher. Further, it is desirable that the difference between the primary crystal temperature and the solidus temperature of the metal containing aluminum as the main component is 15 ° C. or more. Further, the content of silicon carbide in the Al-SiC composite is preferably 40% by volume or more. Still another aspect of the present invention is a heat dissipation component made of the Al—SiC composite of the present invention and a semiconductor module device including the heat dissipation component.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A porous body mainly composed of silicon carbide is impregnated with various kinds of metals containing aluminum as a main component.
As a result of making various studies on the l-SiC-based composite, when the primary crystal temperature of the metal containing aluminum as the main component was 615 ° C. or higher, aluminum was used as the main component when joining the DBA substrate using the aluminum-based brazing material. The metal that does not melt, A
It was possible to prevent the l-SiC-based composite from leaching on the surface. Therefore, the airtightness can be maintained without a decrease in the density inside the Al-SiC-based composite, and the thermal conductivity, bending strength, and Young's modulus of the Al-SiC-based composite are not deteriorated, and are generated from the semiconductor chip. The generated heat can be sufficiently dissipated to the outside. The primary crystal temperature of a metal containing aluminum as a main component is 615 to 6
50 ° C. is more preferable.

If the solidus temperature of the metal containing aluminum as the main component is 560 ° C. or higher, cracks or Al-SiC may occur at the boundary between the Al-SiC composite main body after aluminum impregnation and the aluminum coating layer. It is possible to suppress the occurrence of shrinkage cavities on the surface of the aluminum coating layer of the composite material. A more preferable solidus temperature of a metal containing aluminum as its main component is 560 to 600 ° C. Further, if the difference between the primary crystal temperature and the solidus temperature of the metal containing aluminum as the main component is 15 ° C. or more, cracks at the boundary between the Al—SiC composite main body and the aluminum coating layer, or the surface of the aluminum coating layer. It is even more effective in preventing the occurrence of shrinkage cavities.

If the difference in thermal expansion coefficient between the ceramic substrate and the Al-SiC composite is large, the solder joint surface may peel off. Therefore, the thermal expansion coefficient of the Al-SiC composite should be close to that of the ceramic substrate. The content of silicon carbide therein is preferably 40% by volume or more, and more preferably 50 to 80% by volume. When the content of silicon carbide is less than 40% by volume, the coefficient of thermal expansion becomes large, and when it exceeds 80% by volume, the strength and fracture toughness decrease and the thermal conductivity decreases, which is not preferable.

(Example 1) A heat dissipation component made of an Al-SiC composite according to the present invention was manufactured as follows. First,
A binder and a solvent for a shape-retaining agent were added to silicon carbide powder having an average particle size of 60 μm and a purity of 98% or more, and the mixture was mixed with a stirrer to obtain a silicon carbide slurry. This slurry was poured into a mold having a desired shape, molded, and then cooled to remove the mold. This was dried to prepare a silicon carbide porous body.

Then, the porous body of silicon carbide was loaded into the mold while a predetermined gap was secured between the porous body of silicon carbide and the inner wall of the mold. Then, the heat-melted aluminum was press-fitted and impregnated into a mold charged with a porous body of silicon carbide. After completion of impregnation and cooling, the mold was disassembled to produce a plate-shaped heat dissipation component made of an Al-SiC-based composite having a silicon carbide content of 50% by volume.

The obtained Al-SiC-based composite has a gap between the porous body of silicon carbide and the inner wall of the mold in which the porous body of silicon carbide is charged when the porous body of silicon carbide is impregnated with aluminum. By passing a part of the impregnated aluminum, a metal-rich coating layer containing impregnated aluminum as a main component was formed over the entire surface of the Al—SiC-based composite. The thickness of the coating layer is 50 μm on average, and
No exposure of silicon carbide powder was found on the surface of the 1-SiC-based composite.

In the production of such a heat radiating component, a heat radiating component of the present invention and a comparative example having different kinds of impregnated aluminum were produced. As impregnated aluminum of Inventive Example 1, Al-5.0Si-1.2Cu (primary crystal temperature 625
C., solidus temperature 580.degree. C.) were used. As the impregnated aluminum of the comparative example, the comparative example 1 is Al-7.0Si-.
0.3 Mg (primary crystal temperature 610 ° C., solidus temperature 555
C), Comparative Example 2 is Al-12.0Si (primary crystal temperature 585).
C., solidus temperature 575 ° C.) were used.

Using the heat dissipating component made of these Al--SiC composites, the DBA substrate is heated to a temperature (brazing temperature 590 ° C.) for brazing with an aluminum brazing material, held for a certain period of time, and then cooled. Let After that, each Al
The density, thermal conductivity, bending strength (4-point bending test) and Young's modulus of the -SiC composite were measured. Table 1 shows the measurement results.

[0021] Table 1               density        Thermal conductivity    Bending strength    Young's modulus             (G / cc) (W / mK) (MPa) (GPa) Invention Example 1 2.98 190 420 200 Comparative Example 1 2.88 150 340 170 Comparative Example 2 2.80 130 300 150

From Table 1, in the case of the heat-dissipating component made of the Al-SiC composite of Example 1 of the present invention, since the primary crystal temperature of the metal containing aluminum as the main component is 615 ° C or higher, the main component of aluminum is And the metal does not melt, Al
It did not elute on the surface of the —SiC-based composite, and the density did not decrease. Therefore, the thermal conductivity, bending strength, and Young's modulus of the Al-SiC composite could be maintained at high values.
On the other hand, in Comparative Example 1 and Comparative Example 2, the metal containing aluminum as the main component was melted and melted out on the surface of the Al-SiC-based composite, so that the density was lowered, the thermal conductivity, the bending strength,
All of the Young's moduli were lower than those of Example 1 of the present invention.

(Example 2) In the same manner as in Example 1 described above, a plurality of heat radiating components of the present invention and the comparative example in which the kinds of impregnated aluminum were different were prepared. As the impregnated aluminum of Inventive Example 2, Al-5.0Si-1.2Cu (primary crystal temperature 625 ° C., solidus temperature 580 ° C.) was used. The impregnated aluminum of Comparative Example 3 has a purity of 99.
7% or more pure Al (primary crystal temperature 657 ° C, solidus temperature 64
6 ° C.) was used.

Table 2 shows Al-Si of the present invention and comparative examples.
The result of having evaluated a C type complex is shown. In Table 2, "crack" represents the rate of occurrence of cracks at the boundary between the Al-SiC composite main body and the aluminum coating layer after completion of impregnation. The "shrinkage cavity" represents the rate of occurrence of shrinkage cavity generated on the surface of the aluminum coating layer of the Al-SiC composite.

[0025]

From Table 2, in the Al-SiC composite of Inventive Example 2, the solidus temperature of the metal whose main component is impregnated aluminum is 560 ° C or higher, and the primary crystal temperature and the solidus temperature. Is 15 ° C or more. Therefore, A after impregnation is completed
No cracks were generated at the boundary between the 1-SiC composite main body and the aluminum coating layer, and no shrinkage cavities were observed on the surface of the aluminum coating layer of the Al-SiC composite. In Comparative Example 3, since the difference between the primary crystal temperature and the solidus temperature of aluminum was as small as 11 ° C., cracks and shrinkage cavities were observed.

[0027]

According to the Al-SiC based composite of the present invention, it is possible to prevent the metal containing aluminum as a main component from being melted at the time of joining a DBA substrate using an aluminum based brazing material, and to suppress the Al-SiC based composite. The airtightness inside the body can be maintained and the heat generated from the semiconductor chip can be sufficiently dissipated to the outside.
Further, it is possible to prevent shrinkage cavities and cracks from being generated after press-fitting and impregnating a metal containing aluminum as a main component.

Claims (6)

[Claims] 1. An Al- which is formed by impregnating a porous body mainly composed of silicon carbide with a metal containing aluminum as a main component.
An Al-SiC-based composite, which is a SiC-based composite, wherein a primary crystal temperature of the metal containing aluminum as a main component is 615 ° C or higher. 2. The Al—SiC based composite according to claim 1, wherein the solid phase temperature of the metal containing aluminum as a main component is 560 ° C. or higher. 3. The Al-SiC composite according to claim 1, wherein the difference between the primary crystal temperature and the solidus temperature of the metal containing aluminum as a main component is 15 ° C. or more. 4. The Al-SiC composite according to claim 1, wherein the content of silicon carbide in the Al-SiC composite is 40% by volume or more. 5. The Al- according to any one of claims 1 to 4.
A heat dissipation component comprising a SiC-based composite. 6. A semiconductor module device comprising the heat dissipation component according to claim 5.