JP2001335859A - Aluminum-silicon carbide composite material and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al-SiC composite material capable of preventing deformation and damage by relaxing the strain of thermal stress caused by the diference in thermal expansion coefficients, easily joinable with the other parts at excellent strength, moreover having high thermal conductivity and suitable as a heat radiating substrate or the like. SOLUTION: This composite material is composed of metal consisting essentially of Al and particles consisting essentially of SiC, one end of which is provided with a metallic layer consisting essentially of Al, and in contact with the Al metallic layer, the other end of which is arranged with a compounded in which SiC is dispersed into an Al metal matrix. In the compounded layer, the amount of SiC is stepwise or continuously changed between one end and the other end, and preferably, the amount of SiC is stepwise or continuously increased from the metallic layer side of one end toward the other end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum-silicon carbide composite material suitable as a heat-radiating substrate for mounting a semiconductor element, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, market demands for high-speed operation and high integration of semiconductor devices are rapidly increasing. At the same time, the heat generated from the semiconductor element is more efficiently released to the heat dissipation board for mounting the semiconductor element of the device,
It has been required to further improve the thermal conductivity.

[0003] Also, regarding the thermal expansion coefficient of the heat dissipation board,
In order to further reduce the thermal strain between the element and other peripheral members in the semiconductor device disposed adjacent to the heat dissipation substrate, it is required that the members have a thermal expansion coefficient closer to those members. Specifically, the thermal expansion coefficients of Si and GaAs, which are usually used as semiconductor elements, are each 4.2 ×.
10 ⁻⁶ / ° C. and 6.5 × 10 ⁻⁶ / ° C., which is about 6.5 × 10 ⁻⁶ / ° C. of alumina ceramics usually used as an envelope of a semiconductor device. Is desired to be close to these values.

Further, with the remarkable expansion of the application range of electronic equipment in recent years, the range of use of semiconductor devices has been further diversified. Among them, applications to so-called semiconductor power device devices such as high-output AC converters and frequency converters are increasing. In these power devices, the heat generated by the semiconductor elements is several to several tens of times (typically, for example, several tens of watts) compared to ordinary semiconductor memories and microprocessors. It is even more important that the rate of thermal expansion be significantly improved, and that the coefficient of thermal expansion be consistent with the surrounding members.

Conventionally, as such a heat dissipation substrate for a semiconductor device, for example, a substrate made of a Cu-W or Cu-Mo composite alloy has been generally used. However, the heat-dissipating substrates made of these composite alloys have problems that the cost is high because the raw materials are expensive, and that they are heavy.

Therefore, recently, various aluminum (hereinafter, also simply referred to as Al) composite materials have been attracting attention as inexpensive and lightweight materials. Above all, Al-SiC-based composite materials containing Al and silicon carbide (hereinafter, also simply referred to as SiC) as main components are relatively inexpensive, light-weight, and have high thermal conductivity. Attention has been paid.

Incidentally, pure Al and S which are usually commercially available
In the case of iC alone, the densities are about 2.7 g / cm ^{3 and} about 3.2 g / cm ^3, respectively, and the thermal conductivity is 240 g / cm ^3.
Although it is up to about W / m · K, it is considered that the level of the thermal conductivity is further improved by adjusting the purity and the defect concentration. The thermal expansion coefficients of pure SiC alone and Al alone are about 4.2 × 10 ⁻⁶ / ° C. and 24 × 10
It is about ⁻⁶ / ° C., and by combining them, the thermal expansion coefficient can be controlled in a wide range.

[0008] Such an Al-SiC-based composite material and a method for producing the same are described in (1) JP-A-1-501489, (2) JP-A-2-343729, and (3) JP-A-61-222668. And (4) Japanese Patent Laid-Open No. 9-1
No. 57773. The above (1) uses Si
The present invention relates to a method in which Al in a mixture of C and Al is melted and solidified by a casting method. The above (2)
And (3) all relate to a method of infiltrating Al into the voids of a porous SiC body, and particularly (3) relates to a so-called pressure infiltration method of infiltrating Al under pressure. .

The above (4) is a method of placing a compact of a mixed powder of SiC and Al or a hot-pressed compact in a mold and subjecting the compact to liquid phase sintering at a temperature equal to or higher than the melting point of Al in a vacuum. It is about. Also, the above (4) discloses a method in which a mixture of an Al powder and a SiC powder is hot-pressed to simultaneously perform molding and sintering.
The method is to form a mixed powder of 10 to 80% by volume of Al and the balance of SiC, and to form a mixed powder at a temperature equal to or higher than the melting point of Al.
Hot pressing is performed at a pressure of kg / cm ² or more, and an aluminum-silicon carbide composite material having a thermal conductivity of 150 to 280 W / m · K is obtained.

On the other hand, the present inventors have proposed (5)
335538, (6) JP-A-10-280082
Japanese Patent Application Publication, (7) Japanese Patent Application No. 11-28940 and (8) Japanese Patent Application No. 11-176807 propose Al-SiC-based composite materials. That is, in the above (5), the thermal conductivity obtained by the liquid phase sintering method is 180 W / m · K
The above-mentioned aluminum-silicon carbide composite material is presented. This composite material is formed, for example, by molding a mixed powder of 10 to 70% by weight of particulate SiC powder and Al powder, and then molding the mixed powder.
% Or more of nitrogen, an oxygen concentration of 200 ppm or less, and a dew point of −20 ° C. or less in a non-oxidizing atmosphere.
Obtained by sintering at ~ 750 ° C.

In the above (6), the thermal expansion coefficient is 18 × 10 ⁻⁶ / ° C. or less, and the thermal conductivity is 230 W / m 2.
A so-called net-shape aluminum-silicon carbide composite material having a size of K or more and a size after sintering is close to a practical size is presented. Further, (7) proposes a method combining the normal pressure sintering method and the HIP method, and (8) proposes a method of solidifying by high-temperature forging using high-purity SiC powder.

According to the above (7), for example, particulate SiC
Of Al-SiC-based mixed powder containing 10% to 70% by weight of Al in a non-oxidizing atmosphere containing 99% or more of nitrogen gas at atmospheric pressure within a temperature range of 600 ° C. or more and the melting temperature of Al or less. And then sealed in a metal container for 700
By performing the HIP at a temperature of not less than ° C., an aluminum-silicon carbide composite material having a uniform thermal conductivity of not less than 200 W / m · K can be obtained. Further, according to the above (8), for example, preheating is performed by means capable of rapidly increasing and heating, and hot forging is performed in a mold, so that 250 W /
It is possible to obtain an aluminum-silicon carbide composite material having a m · K or more.

[0013]

As described above, Al-SiC-based composite materials can be obtained by various methods.
When these materials are mounted on a semiconductor device as a heat dissipation board or the like, for example, an aluminum-based metal material having a large thermal expansion coefficient is arranged on one surface, and a ceramic material having a small thermal expansion coefficient is arranged on the other surface. There are many things to do.
In such a case, as the Al-SiC-based composite material disposed between the metal material and the ceramic material, a material having a thermal expansion coefficient intermediate between the two is usually used.

However, at the connection interface between the Al-SiC-based composite material and the metal material or the ceramic material, the distortion of the thermal stress generated due to the difference in the thermal expansion coefficient is not sufficiently relaxed at the time of mounting and thereafter during practical use. It is easy to remain. As a result, there has been a defect that the substrate is deformed after mounting or the substrate is easily damaged by a cooling / heating cycle in practical use.

Further, when mounting the Al-SiC-based composite material as a heat dissipation board or the like, other components are often connected by solder or brazing material. In this case, the surface of the composite material is finished by grinding, but since the SiC particles fall off during the processing and the surface irregularities are likely to become large, plating on the surface becomes difficult to place, or a component bonded to the surface There is also a problem that the connection strength with the cable is likely to decrease.

The present invention has been made in view of such a conventional situation,
During mounting on a semiconductor device and its practical use, the strain of thermal stress due to the difference in thermal expansion coefficient can be relaxed to prevent deformation and damage, and it can be easily joined with other parts with excellent strength and has high thermal conductivity. Al-SiC suitable as a heat dissipation substrate
It is an object to provide a system composite material and a method for producing the same.

[0017]

In order to achieve the above object, an aluminum-silicon carbide based composite material provided by the present invention comprises a metal mainly composed of aluminum and particles mainly composed of silicon carbide. An aluminum-silicon carbide composite material having a metal layer mainly composed of aluminum at one end of the composite material, and carbonized in a metal matrix mainly composed of aluminum at the other end in contact with the metal layer. A composite layer in which particles containing silicon as a main component are dispersed is arranged, and in the composite layer, the amount of silicon carbide is changed stepwise or continuously between the metal layer side and the other end. It is characterized by the following.

[0018] In particular, in the aluminum-silicon carbide based composite material of the present invention, the composite layer is characterized in that the amount of silicon carbide increases stepwise or continuously from the metal layer side to the other end. Features. Further, in this case, the amount of silicon carbide in the composite layer is 50% by volume or less at one end where the composite layer is in contact with the metal layer, and 75% by volume or less at the other end of the composite layer. Is preferred.

The method for producing an aluminum-silicon carbide composite material according to the present invention is a method for producing an aluminum-silicon carbide composite material comprising a metal mainly composed of aluminum and particles mainly composed of silicon carbide. A step of preparing a metal powder containing aluminum as a main component and a silicon carbide powder as raw material powders; and preparing a plurality of types of aluminum-silicon carbide mixed powders having different amounts of silicon carbide by mixing these raw material powders. And placing a layer of a metal powder containing aluminum as a main component at one end, and viewing a layer of a plurality of types of aluminum-silicon carbide-based mixed powder on the other end of the metal powder layer from the metal powder layer side. A step of arranging the silicon carbide content in ascending order, and pressing to form a molded body;
Sintering the molded body in an inert gas at a temperature equal to or higher than the melting point of the metal containing aluminum as a main component contained in the molded body to form a sintered body.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum-silicon carbide composite material of the present invention has a metal layer containing aluminum as a main component at one end, and contacts the metal layer with aluminum as a main component at the other end. A composite layer in which particles containing silicon carbide as a main component are dispersed in a metal matrix to be formed is disposed.
Moreover, the composition of the composite layer has a gradient composition in which the amount of silicon carbide changes stepwise or continuously. Particularly preferably, the amount of silicon carbide in the metal matrix is changed from one end in contact with the metal layer to the other end. It is increasing stepwise or continuously.

Here, the metal containing aluminum as a main component (hereinafter, also simply referred to as an Al-based metal) is used in a sense that it includes not only aluminum alone but also an alloy with another metal containing aluminum as a main component. Particles containing silicon carbide as a main component (hereinafter also simply referred to as SiC-based particles) are made of SiC.
In addition to the particles, the meaning includes SiC particles containing other ceramic components.

In the present invention, the amount of SiC in the composite layer having the gradient composition is preferably 50% by volume or less at one end in contact with the Al-based metal layer. If the amount of SiC at one end in contact with the Al-based metal layer exceeds 50% by volume, the joint between the Al-based metal layer and the composite layer is easily broken after sintering. On the other hand, if the SiC content in the composite layer exceeds 75% by volume, the Al content is too small, so that the wetting of Al and SiC is significantly reduced, and the thermal conductivity is rapidly reduced.
In a preferred embodiment in which the C content is at most 75% by volume or less, particularly in a preferred embodiment in which the silicon carbide content increases stepwise or continuously from one end in contact with the metal layer to the other end, SiC on the opposite side of the Al-based metal layer 75% by volume of SiC at the other end with the largest amount
It is preferable to set the following.

The Al-SiC of the present invention having such a structure
Based composite material has a thermal conductivity of 150 W / m · K at 20 ° C.
As described above, it is preferably 180 W / m · K or more, and has excellent thermal conductivity. In addition, since an Al-based metal layer is provided at one end and a composite layer having a graded composition in which the amount of SiC is changed is provided at the other end, thermal stress due to a difference in thermal expansion coefficient during mounting on a semiconductor device and its practical use. Can be alleviated, and deformation and damage of the substrate can be prevented. In addition, A
Since the l-based metal layer is provided, other components can be easily and easily bonded to the Al-based metal layer using solder or brazing material with excellent strength.

Next, a method for producing the aluminum-silicon carbide composite material of the present invention will be described. First, an Al-based metal powder and SiC-based particles (powder) are prepared and dry-mixed at a predetermined ratio to produce a plurality of Al-SiC-based mixed powders having different SiC contents.

Thereafter, an Al-based metal powder containing no SiC particles is charged into a mold, and is subjected to dry press molding. Without removing the molded body from the mold, A
The l-SiC-based mixed powder is charged and molded in the same manner. By repeating this, a molded body having one end composed of the Al-based metal powder layer and having several layers of Al-SiC-based mixed powder having different compositions continuous with the Al-based metal powder layer on the other end side is obtained. Can be In addition, as a molding method, a method may be used in which a plurality of powders as described above are sequentially loaded into a mold, and then the whole is molded at once. The order of loading the powders into the mold is not limited to the specific example described above, and the powders may be loaded in order from any one side.

In molding the Al—SiC mixed powder, SiC particles which are hard particles and aluminum oxide (Al ₂ O ₃ ) present on the surface of the Al metal particles come into contact with each other during molding,
When the Al ₂ O ₃ film is destroyed, a new surface of Al is generated. The Al nascent surface comes into direct contact with SiC, and the molten Al and Si
C wetting occurs. However, when the molding pressure is less than 400 MPa, a new surface of Al is unlikely to appear, so that wetting does not easily occur during sintering, and the thermal conductivity tends to be slightly lower. Therefore, the molding pressure in the above molding step should be 400 MPa or more. preferable. The molding pressure may be as high as over 400 MPa, but the effect is saturated at about 1000 MPa.

The obtained compact is heated to a temperature higher than the melting point of the Al-based metal used in an inert gas such as nitrogen or argon and sintered to form an Al-SiC-based composite material. Can be. The sintering temperature T (° C.)
When the melting point of the base metal is Tm (° C.), Tm <T <(T
(m + 15). Sintering temperature T
When (Tm + 15) or more, the Al-based metal portion and the portion having a low SiC content are easily deformed during sintering,
This is because it becomes difficult to maintain the shape of the molded body.

The atmosphere during sintering may be normal pressure. With a composition of 100 vol% Al-based metal powder,
Nearly 100% relative density can be obtained even under normal pressure sintering. However, as the amount of SiC increases, it comes to contain pores,
In general, the coefficient of thermal expansion decreases as the amount of porosity increases.
In particular, as described above, when the amount of SiC exceeds 75% by volume, the thermal conductivity sharply decreases. Note that even in such a case, by using a high-purity SiC powder having a high thermal conductivity, a decrease in the thermal conductivity can be suppressed.

If pressure sintering is performed instead of normal pressure sintering, the relative density is improved, and the thermal conductivity of the Al—SiC composite material is also improved. For example, after pre-heating the molded body in an inert gas at a temperature equal to or higher than the melting point of the Al-based metal, by hot forging, the densification proceeds regardless of the SiC content, and a high thermal conductivity is obtained. Can be As described above, the sintering temperature at the time of pressure sintering is also Tm <T <
It is preferable to be in the range of (Tm + 15).

In the method of the present invention, a plurality of Al-SiC-based mixed powder layers having different amounts of SiC are arranged on the other end side of the Al-based metal powder layer to thereby obtain an Al-SiC-based mixed powder layer obtained by sintering. Since the thermal expansion coefficient of the composite material changes stepwise or continuously, the thermal stress generated during sintering, the cooling process after sintering, and during practical use can be reduced, and Al-S
Deformation and breakage of the iC-based composite material can be prevented. still,
In the Al-SiC-based composite material of the present invention, the amount of SiC may be inclined not only in one direction but also in a plurality of directions if it is stepwise or continuous. For example, depending on the place of use, a structure may be adopted in which a central portion has a high SiC content, and the SiC content decreases gradually toward both ends. Conversely, there may be a structure in which a portion having a small SiC content is provided at the center portion, and the SiC content is gradually increased toward both ends. Furthermore, a structure combining these may be used.

[0031]

【Example】Example 1  Commercially available SiC powder having an average diameter of 80 μm and melting point of 659 ° C.
Of pure Al (99.9%) powder was prepared. This SiC powder
Powder and Al powder are mixed so that the amount of SiC is
0 (Al powder), 30, 50, 70 each mixture
A powder was made.

Next, the above-mentioned Al is placed in a mold having an inner diameter of 35 mm.
The powder was charged and pressed at a pressure of 400 MPa. On the molded body in the mold leaving the obtained molded body as it is,
The above mixed powder was charged and press-molded similarly. As described above, the charging and press molding of each of the above-mentioned powders were repeated, and finally a molded body having a gradient composition was produced.

With respect to the molded body thus produced,
660 ° C., 674 ° C., 681 in a nitrogen gas atmosphere
Heating was performed at each temperature of 700C and 700C for 2 hours, and sintering was performed to produce Al-SiC-based composite materials each having a gradient composition. As a result, those sintered at 660 ° C. and 674 ° C. did not deform or break, but those sintered at 681 ° C. and 700 ° C. expanded the Al layer portion in the radial direction, and the diameter of the portion was changed to 38 mm. I was FIG. 1 schematically shows the sectional structure of each layer of the sample sintered at 674 ° C. In each layer of this sample, the SiC amount was 0% by volume from the left side of FIG.
The order of each layer of 30% by volume, 50% by volume, and 70% by volume is in that order.
C.

As a comparative example, only a mixed powder (70% by volume of SiC) mixed with the Al powder was charged into a mold, pressed and sintered in the same manner as described above, and a composite material consisting of only two layers was prepared. Was prepared. However, the composite material of this comparative example was broken at the interface with the composite material during sintering.

From each part having the above composition of each of the Al-SiC-based composite materials of the above embodiments, a diameter of 10 mm
A sample having a shape of × 2 mm in thickness and 5 mm in diameter × 10 mm in thickness was cut out, and the thermal conductivity and the coefficient of thermal expansion at 20 ° C. were measured. Table 1 shows the Al sintered at 674 ° C.
-For a SiC-based composite material sample, the relative density, the thermal conductivity at 20 ° C, and the thermal expansion coefficient of each of the composition parts are shown.

[0036]

TABLE 1 sets formed relative density heat conductivity thermal expansion coefficient unit content (%) (W / m · K) (ppm / K) 100 238 23 98 225 17.5 94 203 12 89 156 7.5

For the purpose of comparison, the layers in contact with the Al-based metal layer are omitted from the layers of FIG.
A sample A in which a layer of 70% by volume was formed as a layer of
A sample B having a layer of 78% by volume of SiC instead of the layer having the largest C content was sintered at 674 ° C. in the same manner as described above. As a result, in sample A, the Al-based metal layer and the SiC
A minute gap was confirmed at a part of the outer diameter of the interface with the 55% by volume layer. In sample B, the relative density of the 78% by volume SiC layer was 79%, and the thermal conductivity of that portion was 102%.
W / m · K. The same commercially available SiC powder was previously immersed in hydrofluoric nitric acid to remove 100 ppm of cation impurities such as Fe.
In Sample C sintered at 674 ° C. in the same configuration as Sample B using a higher purity SiC powder reduced to below pm, the relative density was 88%, but the heat of the layer of 78% by volume of SiC was The conductivity increased to 120 W / m · K, and the thermal conductivity of the other layers also improved to 170 W / m · K or more.

[0038]Example 2  Commercially available SiC powder having an average diameter of 80 μm and a melting point of 635 ° C.
No. 6061 Al alloy powder was prepared. This Al alloy powder
And SiC powder are mixed so that the amount of SiC is
Each of 0 (Al alloy powder), 20, 40, 60
A mixed powder was prepared. Next, the above mold was placed in a mold with an inner diameter of 35 mm.
And press at 800MPa
Molded. The mold in the mold leaving the obtained compact as it is
Load the above mixed powder on the form and press similarly
Molded. Thus, the loading and pressing of
Molding, and finally a molded body with a gradient composition
Produced.

The obtained compact was heated and sintered at 636 ° C., 649 ° C., and 655 ° C. for 2 hours in a nitrogen gas atmosphere.
A C-based composite material was produced. These composite materials were again heated to 655 ° C. in a high-frequency induction heating furnace in a nitrogen gas atmosphere, filled in a steel mold having an inner diameter of 36 mm kept at 450 ° C., and hot forged at a pressure of 900 MPa. as a result,
Those sintered at 636 ° C. and 649 ° C. had no deformation or breakage before forging, whereas those sintered at 655 ° C. had the Al alloy layer portion deformed to 37 mm in diameter before forging.

As a comparative example, only a mixed powder (60% by volume of SiC) with the above-mentioned Al alloy powder was charged into a mold, pressed and sintered in the same manner as described above, and a composite consisting of only two layers was formed. Materials were made. However, the composite material of this comparative example broke during sintering at the interface between the and layers.

From each part having the above composition of each of the Al-SiC-based composite materials (forged bodies) of the above embodiment, a diameter of 10 mm × a thickness of 2 mm and a diameter of 5 mm × a thickness of 10 mm
Was cut out, and the thermal conductivity and the coefficient of thermal expansion at 20 ° C. were measured. Table 2 below shows the relative densities, the thermal conductivities at 20 ° C., and the coefficients of thermal expansion at 20 ° C. for the Al—SiC-based composite material samples sintered at 636 ° C.

[0042]

Table 2 sets formed relative density heat conductivity thermal expansion coefficient unit content (%) (W / m · K) (ppm / K) 100 180 23 100 192 19.5 100 220 15 100 244 10

The same commercially available SiC powder was previously immersed in hydrofluoric acid to reduce the amount of cation impurities such as Fe to 100 ppm or less, and a higher purity SiC powder was used. In sample D prepared by the composite solidification method by sintering and forging, the thermal conductivity of each layer was 180, 205, 236, 259 W / m · K in the order from above.
And improved.

[0044]Example 3  Inclination obtained by the same manufacturing method as the samples of Examples 1 and 2 described above.
50 pieces of each of the Al-SiC-based composite materials having a composition of length 2
Finished on a base material of 00mm x 200mm x 6mm
Worked. Similarly, a single composition A containing 50% by volume of SiC
The l-SiC composite material (not the graded composition) was prepared in Example 2
After the same solidification method by sintering and forging as above,
A base material finished to the same shape as that described above was also prepared.

These substrates were mounted on a power module as schematically shown in FIG. 2 as a heat dissipation substrate, and a temperature cycle test was conducted including the mounting stage. In FIG. 2, 1
Is a radiating substrate made of a base material of each of the above composite materials, 2 is disposed on the radiating substrate 1, and an Al circuit (not shown) is provided on the upper surface thereof.
Electrically insulating ceramic substrate on which is formed, 3 is Si
The semiconductor element 4 is a heat dissipation structure disposed below the heat dissipation board 1. Although the heat radiation structure 4 is a water-cooled jacket made of an aluminum alloy, there are other air-cooled fins.
In FIG. 2, wirings around the Si semiconductor element 3 and the like are omitted. In this embodiment, a module in which six Si semiconductor elements 3 are mounted via the ceramic substrate 2 is used.

Prior to mounting, the ceramic substrate 2 cannot be directly soldered to the main surface of the heat radiating substrate 1 on the side where the amount of SiC is large, so that an electroless nickel plating layer having an average thickness of 5 μm and an electroless nickel plating layer having an average thickness of 3 μm An electrolytic nickel plating layer was formed. For each of the four specimens of each sample, a copper wire having a diameter of 1 mm was attached on a nickel plating layer by a hemispherical Ag-Sn-based solder having a diameter of 5 mm in a direction perpendicular to the plating surface. The heat radiating substrate 1 of this sample was fixed to a jig, the copper wire was grasped and pulled in a direction perpendicular to the plating surface, and the adhesion strength of the plating layer to the heat radiating substrate 1 was confirmed. As a result, the plating layer of any heat radiation substrate 1 was 1 kg /
It did not peel off even with a pulling force of ² mm or more.

Next, as the ceramic substrate 2 mounted on the heat radiating substrate 1, the thermal conductivity is 150 W / m · K, the thermal expansion coefficient is 4.5 × 10 ⁻⁶ / ° C., and the three-point bending strength is 450.
A substrate A made of aluminum nitride of MPa and a thermal conductivity of 1
20 W / m · K, coefficient of thermal expansion 3.7 × 10 ⁻⁶ / ° C, 3
A substrate B made of silicon nitride having a point bending strength of 1300 MPa,
Eight each of two types of substrates each having an Al circuit formed on the main surface were prepared. The shape of these ceramic substrates 2 is
In each case, the length was 90 mm × the width 60 mm × the thickness 1 mm. These ceramic substrates 2 are used as the heat radiation substrates 1
Were arranged at equal intervals in two rows and three columns on a 200 mm square main surface (side with a large amount of SiC), and fixed on the surface on which the nickel plating layer was formed by Ag-Sn solder. In addition, Si
A heat dissipation substrate composed of a base material of a single composition Al-SiC composite material (not a gradient composition) containing 50% by volume of C was similarly assembled.

Thereafter, a water-cooling jacket, which is a heat radiation structure 4, is opposed to the main surface made of Al on the opposite side of the ceramic substrate 2 of the heat radiation substrate 1 in these assemblies, and a silicone oil compound is applied to the contact surface between the two. Then, it was bolted and fixed. The mounting holes for the bolts were radiated with carbon dioxide laser to the prepared holes previously drilled at the four corners of the heat dissipation board at the material stage, and the holes were sized to 3 mm in diameter.
It was formed by a method of spreading out. This processing method could be performed with high accuracy and at high speed as compared with the case of using other ceramic materials and Cu-W or Cu-Mo. This tendency was particularly remarkable as the thermal conductivity of the heat-dissipating substrate as a processing material became higher.

From each of the obtained test pieces, 15 ceramic substrates 2 each having a substrate A and a substrate B were selected.
Under a single cycle condition of holding for 30 minutes at 150 ° C. and then for 30 minutes at 150 ° C., a heat cycle test was performed from 1000 cycles to 3000 cycles, which is considered to be practically no problem, and the output change of the module every 100 cycles was measured. confirmed. As a result, in the test piece using the heat dissipation substrate made of the two kinds of gradient composite materials of the present invention, no decrease in output was observed to the end. On the other hand, in the test piece using the heat-dissipating substrate made of a single-composite composite material (not a gradient composition) containing 50% by volume of SiC, a slight decrease in output was confirmed at the 2500th cycle, and the cross section of the interface on the water cooling jacket side was confirmed. A small crack was observed in the sample. From the above results, it can be seen that the power module using the heat-dissipating substrate made of the Al-SiC-based composite material having the gradient composition of the present invention can be put to practical use with considerably higher reliability than a practically acceptable level. I understand.

As described above, in the Al-SiC-based composite material of the present invention, since the composition of the Al-SiC-based composite layer has a gradient composition from the Al-based metal layer at one end to the other end, the thermal composition of the Al-SiC-based composite layer is inclined. The conductivity and the coefficient of thermal expansion change stepwise, so that deformation and destruction can be prevented, and high thermal conductivity can be exhibited. When one of the ceramic members has a small coefficient of thermal expansion and the other is a metal member having a large coefficient of thermal expansion, one of the ceramic members may be made of the Al material of the present invention.
When the side having a large amount of SiC of the SiC-based composite material is bonded and the Al metal side is bonded to the other metal member and used, compared with the conventional single-composition Al-SiC composite material, higher reliability is obtained. A semiconductor device can be provided.

Further, the gradient composition of the Al—SiC-based composite material of the present invention is not limited to the stepwise composition as in the above-mentioned specific example, and the composition change of each mixed powder is made fine, and a large number of mixed powder layers are formed. By arranging, it is also possible to obtain a gradient composition that changes continuously.

[0052]

According to the present invention, a metal layer mainly composed of Al is provided at one end, and a composite layer having an Al-SiC-based graded composition is provided at the other end, and has a high thermal conductivity. It is possible to provide an Al-SiC-based composite material in which the thermal conductivity and the coefficient of thermal expansion change stepwise or continuously. Therefore, the Al-SiC-based composite material of the present invention is suitable as a heat-radiating substrate mounted on a semiconductor device. Can be prevented, and other parts can be joined to the metal layer easily and with excellent strength.

[Brief description of the drawings]

FIG. 1 is a drawing schematically showing an Al—SiC-based composite material of the present invention and a cross-sectional structure of each layer thereof.

FIG. 2 is a cross-sectional view schematically showing a power module using the Al—SiC-based composite material of the present invention as a heat dissipation substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat dissipation board 2 Ceramics board 3 Si semiconductor element 4 Heat dissipation structure

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Claims (10)

[Claims] An aluminum-silicon carbide composite material comprising a metal containing aluminum as a main component and particles containing silicon carbide as a main component, and a metal layer containing aluminum as a main component at one end of the composite material. A composite layer in which particles mainly composed of silicon carbide are dispersed in a metal matrix mainly composed of aluminum in contact with the metal layer on the other end side, and the composite layer is An aluminum-silicon carbide-based composite material, wherein the amount of silicon carbide changes stepwise or continuously between the metal layer side and the other end. 2. The aluminum alloy according to claim 1, wherein the amount of silicon carbide in the composite layer increases stepwise or continuously from the metal layer side toward the other end.
Silicon carbide composite material. 3. The amount of silicon carbide in the composite layer is 50% by volume or less at one end where the composite layer is in contact with the metal layer, and 75% by volume or less at the other end of the composite layer. The aluminum-silicon carbide-based composite material according to claim 2, characterized in that: 4. The thermal conductivity at 20 ° C. is 150 W / m · K.
The aluminum-silicon carbide-based composite material according to any one of claims 1 to 3, wherein: 5. The thermal conductivity at 20 ° C. is 180 W / m · K.
The aluminum-silicon carbide composite material according to claim 4, wherein: 6. A semiconductor device using the aluminum-silicon carbide composite material according to claim 1 as a heat dissipation substrate. 7. A method for producing an aluminum-silicon carbide composite material comprising a metal mainly composed of aluminum and particles mainly composed of silicon carbide, wherein a metal powder mainly composed of aluminum is used as a raw material powder. A step of preparing silicon carbide powder, a step of mixing these raw material powders to prepare a plurality of types of aluminum-silicon carbide-based mixed powders having different amounts of silicon carbide, and a step of mixing metal powder containing aluminum as a main component at one end. Along with disposing the layers, layers of a plurality of types of aluminum-silicon carbide-based mixed powder are arranged on the other end side of the metal powder layer in ascending order of the silicon carbide content when viewed from the metal powder layer side, and pressure-formed. Forming a molded body, and sintering the formed body in an inert gas at a temperature equal to or higher than the melting point of a metal containing aluminum as a main component contained in the formed body to form a sintered body. A method for producing an aluminum-silicon carbide composite material, comprising: 8. The molding pressure in the step of forming a molded body is 40.
The method for producing an aluminum-silicon carbide composite material according to claim 7, wherein the pressure is 0 MPa or more. 9. A sintering temperature T for the step of forming a sintered body.
(° C.) is defined as Tm (° C.) where the melting point of a metal containing aluminum as a main component contained in the compact is Tm (° C.).
The method for producing an aluminum-silicon carbide composite material according to claim 7, wherein the relationship of (Tm + 15) is satisfied. 10. In the step of forming the sintered body, the formed body is preliminarily heated in an inert gas at a temperature equal to or higher than the melting point of a metal containing aluminum as a main component contained in the formed body. Characterized by being forged by:
10. The method for producing an aluminum-silicon carbide composite material according to any one of items 9.