JP2000303126A - Diamond-aluminum composite material and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diamond-aluminum-based composite material having a high thermal conductivity which is useful for a heat dissipation substrate, especially for a semiconductor device. SOLUTION: This is a diamond-aluminum composite material containing diamond particles as a first component and a metal mainly composed of aluminum as a second component, and has a thermal conductivity at 25 ° C. of zW / m · m. K, when the content of the diamond particles is x% by weight, at 5 ≦ x, −
0.0029x ² + 0.141x + 281.08 ≦ z ≦
Diamond satisfy the relationship 0.2239x ² -12.017x + 593.93 - is an aluminum-based composite material. For this material, a raw material containing the first component and the second component is mixed and molded, and the molded body is pre-heated at a temperature equal to or higher than the melting point of the metal mainly composed of aluminum, and hot forged in a short time. Obtained by

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-dissipating substrate used for various devices and equipment, in particular, a diamond-silicon carbide composite material having high thermal conductivity used for a heat-dissipating substrate of a semiconductor device, and a semiconductor device using the same. About.

[0002]

2. Description of the Related Art In recent years, market demands for high-speed operation and high integration of semiconductor devices have been rapidly increasing. At the same time, the heat radiation board for mounting the semiconductor element of the device has been required to further improve the thermal conductivity in order to more efficiently release the heat generated from the element. Furthermore, other elements in the same device and the same device arranged adjacent to the same substrate
In order to further reduce the thermal strain between them and the (peripheral member), it is also required to have a thermal expansion coefficient closer to them. Specifically, Si usually used as the semiconductor element, the thermal expansion coefficient of GaAs are each ^{4.2 × 10 -6 /℃,6.5×10 -6 / ℃} ,
Since that of alumina ceramics usually used as an envelope of a semiconductor device is about 6.5 × 10 ⁻⁶ / ° C., it is desired that the thermal expansion coefficient of the substrate be close to these values.

[0003] Further, with the remarkable expansion of the application range of electronic equipment in recent years, the use range 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 devices, the heat generated by the semiconductor elements is several times to several tens times (typically, for example, several tens of watts) compared to semiconductor memories and microprocessors.
Extend to For this reason, it is important for the heat radiation board used in these devices to remarkably improve the thermal conductivity and to improve the matching of the thermal expansion coefficient with that of the peripheral members. On the other hand, there are devices such as semiconductor memories and microprocessors that do not generate as much heat as the power devices described above in practical use. Since such devices are manufactured in large quantities, they are required to be cheaper than power device devices. Therefore, the heat dissipation board used for this purpose does not need to have high heat dissipation as described above, but is inexpensive. As described above, the level of heat radiation required for the substrate varies depending on the output capacity of the device and its practical function level. Also, the degree of matching of the thermal expansion coefficient required for the substrate varies depending on the structure around the substrate in each device.

[0004] In the case of a power device, a typical basic structure is as follows, for example. First, a Si semiconductor element is mounted on a high thermal conductive aluminum nitride (hereinafter, also simply referred to as AlN) ceramic substrate which is a first heat dissipation substrate. Next, a second heat radiating substrate made of a metal having higher thermal conductivity such as copper is arranged under the first heat radiating substrate. Further, a heat dissipating mechanism capable of water cooling or air cooling is disposed below the second substrate. The above structure allows heat to escape to the outside without delay. Therefore, a complicated heat dissipation structure is inevitable. In this structure, assuming that AlN ceramics of about 170 W / m · K is used as the first heat radiation substrate, the second heat radiation substrate transfers the heat transmitted from the first substrate to the heat radiation thereunder. It is necessary to escape to the mechanism without delay. For this reason, the second substrate has a high thermal conductivity of at least 200 W / m · K at room temperature and a thermal expansion coefficient of at least 10 × 10 ⁻⁶ / ° C.
In particular, a material having a low coefficient of thermal expansion of 8 × 10 ⁻⁶ / ° C. or less is required.

In particular, among power devices which generate a large amount of heat in practical use, the temperature of the radiating substrate itself may rise to 100 ° C. or more, so that a high thermal conductivity at such a temperature is required. In some cases. Therefore, a material having a thermal conductivity of 150 W / m · K or more is required even at such a temperature. Also, the larger the capacity, the more S
The size of the i semiconductor element also increases. Therefore, the heat dissipating substrate on which it is mounted must be enlarged. For example, a substrate for a personal computer has a size of at most about 20 to 40 mm square, while a power device having a large capacity is required to have a size exceeding 200 mm square. In such a large substrate, it is required that not only the dimensional accuracy at the time of mounting but also the accuracy does not decrease at high temperatures. That is, when the substrate is warped or deformed at a high temperature, a gap is formed at an interface with a heat radiation mechanism (such as a radiator or a fin) disposed below the substrate, thereby lowering the heat radiation efficiency. In the worst case, the semiconductor element may be destroyed. Therefore, ensuring excellent thermal conductivity of the heat dissipation board at high temperatures is an important issue.

As the heat radiation substrate used in the various devices described above, for example, a substrate made of a composite alloy of, for example, Cu-W or Cu-Mo has been used. These substrates are expensive because the raw materials are expensive. There is a problem that the weight is further increased. Therefore, recently, various aluminum (hereinafter, also simply referred to as Al) composite alloys have been attracting attention as inexpensive and lightweight materials. Above all, Al-SiC-based composite alloys containing Al and silicon carbide (hereinafter also simply referred to as SiC) as main components are relatively inexpensive, lightweight, and have high thermal conductivity. Note that the density of pure Al and SiC which are usually commercially available are about 2.7 g / cm ^{3 and} about 3.2 g / cm ³ , respectively, and the thermal conductivity is about 240 W / m · K and 200 to 300 W, respectively.
/ M · K, but it is expected that the level of thermal conductivity will be further improved by further adjusting its purity and defect concentration. Therefore, it is a material that has received special attention. The thermal expansion coefficients of pure SiC alone and Al alone are about 4.2 × 10 ⁻⁶ / ° C. and about 24 × 10 ⁻⁶ / ° C., respectively. It becomes controllable in the range. Therefore, this point is also advantageous.

[0007] The Al-SiC-based composite alloy and the method for producing the same are described in (1) Japanese Patent Application Laid-Open No. 1-1501489, (2) Japanese Patent Application Laid-Open No. 2-343729, and (3) Japanese Patent Application Laid-Open No. Sho 6
1-222668 and (4) JP-A-9-1577.
No. 73 is disclosed. (1) relates to a method in which Al in a mixture of SiC and Al is melted and solidified by a casting method. (2) and (3) are both Si
The present invention relates to a method of infiltrating Al into voids of a C porous body. (3) relates to a so-called pressure infiltration method in which Al is infiltrated under pressure. Further, (4) relates to a method of sintering a compact of a mixed powder of SiC and Al or a hot-pressed compact thereof in a mold and subjecting the compact to a liquid phase sintering at a temperature equal to or higher than the melting point of Al in a vacuum. It is.

The present inventors disclosed in Japanese Patent Application No. Hei 9-136164 (5) an aluminum-silicon carbide composite material obtained by a liquid phase sintering method and having a thermal conductivity of 180 W / m · K or more. Is presented. This composite material is, for example, 10-7
After molding a mixed powder of 0 wt% of particulate SiC powder and Al powder, it contains 99% by volume of nitrogen and has an oxygen concentration of 20%.
It is obtained by a step of sintering at 600 to 750 ° C in a non-oxidizing atmosphere having 0 ppm or less and a dew point of -20 ° C or less. Further, the present inventors have disclosed in Japanese Patent Application No. 9-93467 that (6) its thermal expansion coefficient is 18 × 10 ⁻⁶ / ° C. or less, its thermal conductivity is 230 W / m · K or more, A so-called net-shaped aluminum-silicon carbide composite material whose subsequent dimensions are close to practical dimensions is also proposed. Further, the present inventors have proposed in Japanese Patent Application No. 10-41447 a method (7) for producing the same composite material by combining the normal pressure sintering method and the HIP method. According to this, for example, a compact of an Al—SiC-based mixed powder in which 10 to 70% by weight of particulate SiC is mixed is placed in a non-oxidizing atmosphere containing 99% or more of nitrogen gas.
By normal pressure sintering in the temperature range of 600 ° C. or more and Al melting temperature or less, and then sealed in a metal container and HIPed at a temperature of 700 ° C. or more, it is homogeneous and has a thermal conductivity of 200 ° C.
An aluminum-silicon carbide based composite material of W / m · K or more has been obtained.

Further, (8) Japanese Patent Application Laid-Open No. 9-157773 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 500 kg /
Hot pressing is performed at a pressure of ² cm ² or more. According to this method, an aluminum-silicon carbide composite material having a thermal conductivity of 150 to 280 W / m · K is obtained.

However, in the Al-SiC-based composite material described above, the thermal conductivity is at most about 300 W / m · K when the amount of SiC is 80% by weight or less. The lower limit of the coefficient of thermal expansion is about 5 × 10 ⁻⁶ / ° C. Therefore, there is a need for a heat sink material having a thermal expansion coefficient closer to that of a semiconductor element and having a higher thermal conductivity. Under such circumstances, attempts have been made to add diamond having a high thermal conductivity as a third component to them. Diamond may be 20 depending on the crystal system.
A thermal conductivity of 00 W / m · K is also obtained.

For example, Key Engineering
Materials, Vol. 127-131 (1997), pp. 141-152, report the results of research on diamond-Al-SiC systems. The method is as follows. After molding a mixture of 55% by volume diamond powder and 20% by volume SiC powder,
The particle surface of the compact is coated with SiC by a gas phase method to form a preform, and then aluminum is infiltrated into the pores. By this method, an almost dense composite material is obtained. However, its thermal conductivity is at most 325 W / m.
K.

The results of an investigation by the present inventor for the cause are as follows. The reactivity between diamond and molten aluminum is very high. Therefore, at the time of infiltration, aluminum carbide (Al ₄ C ₃ ) having a low thermal conductivity is formed at both interfaces. As a result, the high thermal conductivity of diamond cannot be utilized. In the infiltration method, molten aluminum is usually infiltrated into a formed body having a thickness of about several mm to 10 mm. In order to sufficiently infiltrate the molten aluminum in the thickness direction, it takes several tens of hours for spontaneous infiltration and several minutes for pressure infiltration, and the amount of the above product increases with time. Therefore, in order to lower the surface tension of aluminum and infiltrate aluminum in a shorter time, heating to about 900 ° C., which is considerably higher than its melting point, may be considered. However, as the temperature increases, the formation reaction of the compound proceeds more rapidly. In the method of the above document, the surface of diamond particles is coated with SiC to suppress the reaction, but the effect is small. In any case, the infiltration method including the method of the above-mentioned literature inevitably produces the above-mentioned product to some extent. This problem can also be avoided by a method of sintering a mixture of three components (sintering method), a method of hot pressing (hot pressing method), and a method of melting aluminum in the mixture and casting it into a mold (casting method). I can't.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide an unprecedented heat-sink material having excellent thermal conductivity, which makes use of the high thermal conductivity of diamond. Therefore, the problem is to suppress the reaction between diamond and a metal mainly composed of aluminum as described above, and to reduce the SiC.
An object of the present invention is to provide a diamond-silicon carbide composite material in which the interface between the components, including both, is completely adhered.

[0014]

Means of the present invention for solving the above problems are as follows. That is, the composite material of the present invention is a diamond-aluminum-based composite material containing diamond particles as a first component and a metal mainly composed of aluminum as a second component, and has a thermal conductivity at 25 ° C. of the composite material. Assuming that zW / m · K and the content of diamond particles are x% by weight, z is a diamond-aluminum composite material satisfying the relationship of the following formula (1) when 5 ≦ x. −0.0029x ² + 0.141x + 281.08 ≦ z ≦ 0.2239x ² -12.017x + 593.93 Formula (1) Further, in the present invention, the first component,
A composite material which contains a third component composed of silicon carbide particles in addition to the second component, and in which the total amount of the first component and the third component is within a range satisfying 30 to 80% by weight is also included.

In the present invention, within the above range,
When x is 10% by weight or more, a diamond-aluminum-based composite material satisfying the relationship of the following formula (2) is also included. −0.0074x ² + 1.162x + 291.18 ≦ z ≦ 0.2239x ² -12.017x + 593.93 Formula (2) Further, within the above range, when x is 30% by weight or more, z is A diamond-aluminum-based composite material that satisfies the relationship of the following formula (3) is also included. −0.0136x ² + 5.0264x + 246.19 ≦ z ≦ 0.2239x ² -12.017x + 593.93 Equation (3)

Further, the present invention includes a semiconductor device using any of the above-mentioned consolidation materials.

In the method for producing a consolidated material according to the present invention, a step 1 of preparing a raw material containing the first component and the second component is mixed with the raw material so that the amount of the first component is 5% by weight or more. Step 2 of forming a mixture by mixing, and Step 3 of forming the mixture into a molded body, and Step 4 of preheating the molded body at a temperature equal to or higher than the melting point of the second component and forging to form a forged body. Is the way. Also, in the present invention, the first component in the above step 1,
In addition to the second component, a third component material consisting of silicon carbide particles is prepared. In step 2, the amount of the second component is 20 to 70% by weight, and the total amount of the first component and the third component is A method in which the mixture is mixed to be 30 to 80% by weight to form a mixture is also included. Further, the present invention includes a method of using diamond powder containing Ib-type or IIa-type crystal particles as a raw material of the first component prepared in the above step 1.

[0018]

DETAILED DESCRIPTION OF THE INVENTION The diamond-aluminum system provided by the present invention (hereinafter simply referred to as diamond-Al
In the composite material, the second component is made of a metal containing aluminum (hereinafter, also simply referred to as Al) as a main component. Conventional consolidation materials containing silicon carbide as a main component have been produced by the infiltration method, the sintering method, the casting method, and the hot pressing method as described above. However, since the heating time is relatively long in either method, the above-mentioned Al
The reaction product of low thermal conductivity, aluminum carbide (Al ₄ C ₃ ), is formed at many portions of the interface between diamond and diamond.
This reaction also occurs between Al and SiC.

The present inventors have already filed Japanese Patent Application No. Hei 10-2600.
In No. 03, the heating time was shortened between Al and SiC,
In order to suppress these mutual reactions, Al-
A composite of SiC-based material was proposed. However, in this method, it is necessary to use relatively pure SiC powder in order to obtain a material having a high thermal conductivity exceeding 300 W / m · K. For this reason, special treatment is required to select high-purity SiC powder or to increase the purity of commercially available SiC powder. The upper limit of the thermal conductivity is 350 W /
m · K. In order to obtain an even more thermally conductive Al-SiC-based material, the present inventor referred to the knowledge of the hot forging method described above and changed the total amount of SiC or a part thereof to diamond. As a result of research on Al-based composite materials, the present invention has been completed.

As already mentioned, the diamond of the present invention
The Al-based composite material contains diamond particles in an amount of 5% by weight or more. Below this amount, the effect of improving the thermal conductivity by adding diamond is small. Thermal conductivity zW / m of this material
-There is a relation of the formula (1) between K and the diamond content x. Furthermore, the present invention provides, within the above range,
A third component comprising silicon carbide particles is contained in addition to the first component and the second component, and the total amount of the first component and the third component is 30.
Composite materials in the range satisfying 〜80% by weight are also included. If the amount is less than the lower limit, the shape of the molded body is likely to collapse when the metal mainly containing aluminum is melted by heating after molding. If the amount exceeds the upper limit, the amount of the metal containing aluminum as a main component to be melted becomes small, and it is difficult to proceed with densification. As is clear from the formula (1), in the above composition range, a material having a thermal conductivity of at least 273 W / m · K can be obtained.

FIG. 1 shows the relationship between the equations (1) to (3). The bottom line is z = -0.0029x ² +0.141
x + 281.08 (where x ≧ 5), and the line above it is z = −0.0074x ² + 1.162x + 291.1
8 (where x ≧ 10), and the line above z = −0.
0136x ² + 5.0264x + 246.19 (where x ≧ 30), and the top line is z = 0.223
9x ² -12.017x + 593.93 (provided that 80 ≧
(x ≧ 5). For example, x =
50, ie when the amount of diamond particles is 50% by weight,
The value of z is 28 in W / m · K unit from the bottom in order.
1, 301, 464, and 1065. Therefore, for example, when the amount of diamond is 50% by weight, the thermal conductivity is 28%.
Materials in the range of 1-1065 W / mK are included in the present invention.

The present invention also includes a diamond-aluminum composite material satisfying the relationship of the formula (2) when x is 10% by weight or more within the above composition range. As is clear from the formula (2), in this composition range (the range of the amount of diamond is 10 to 80% by weight), a material having a thermal conductivity of at least 297 W / m · K or more can be obtained. Further, the present invention provides x within the above composition range.
Is 30% by weight or more, z includes a diamond-aluminum-based composite material satisfying the relationship of the formula (3). As is clear from the equation (3), in this composition range (the range of the diamond amount is 30 to 80% by weight), at least 3
A material having a thermal conductivity of 85 W / m · K or more can be obtained.

The present invention also includes a semiconductor device using the above-described composite material as a member, particularly, a heat dissipation substrate.
For example, there is a power module shown in FIG. FIG.
Wherein 1 is a second heat radiation substrate made of the above-described composite material of the present invention, 2 is disposed on the substrate, and an electrically insulating first material made of ceramics (not shown) formed with a copper circuit (not shown) on its upper surface. Reference numeral 3 denotes a Si semiconductor element, and reference numeral 4 denotes a heat radiating structure disposed below the second heat radiating substrate. The jacket is usually composed of a water-cooled jacket, an air-cooled fin, or the like. It should be noted that wiring and the like around the semiconductor element are omitted in FIG. As described above, the composite material of the present invention has an extremely high thermal conductivity than before, and has a thermal expansion coefficient of a ceramic envelope material such as Si and other semiconductor elements and its surrounding alumina and aluminum nitride. Or, because of good matching, it is particularly useful as a heat dissipation board for the power module described above.

The composite material of the present invention is manufactured by the above-described manufacturing method. Diamond powder prepared in step 1, S
The powder containing iC particles as the main component and the powder containing aluminum as the main component may be generally commercially available, and have a particle size,
There are no restrictions on the purity and crystal form, but it is desirable that the thermal conductivity of the substance itself be high. Therefore, it is desirable that all powders have as high a purity as possible. As the diamond powder, it is desirable to use powder composed of Ib-type or IIa-type crystal type particles having high purity and particularly high thermal conductivity among diamonds. For the above-mentioned reason, the amount of the first component is in the range of 5 to 80% by weight. When the first component and the third component are used together, their total amount is
It is desirable that the content be in the range of 30 to 80% by weight.

The mixing method in step 2 may be any known means. When mixing means involving grinding are used, for example, the walls of the container in direct contact with the powder must be free of impurities (such as transition metal impurities and their oxides) that reduce wear and impair the thermal conductivity of the final product. In order to avoid this, it is desirable to devise a material such as SiC as a main component or coating with diamond. In order to avoid mixing of impurities from the vessel wall at the time of mixing, it is desirable to employ a mixing method without pulverization. In the case of the wet mixing method, the solvent is preferably a non-aqueous solvent to prevent oxidation of aluminum. When a medium is used for mixing (for example, a ball of a ball mill), it is desirable to perform the same contrivance as the above-described container wall.

The molding method in step 3 may be a known method, but in the case of molding regardless of a wet type or a dry type, a mold or a vessel wall which becomes a passage of powder due to the molding is made of a wear-resistant material. I do. Therefore, if possible, the wall is
It is desirable to devise a material containing C as a main component or coating with diamond.

In step 4, the compact is heated to a temperature equal to or higher than the melting point of the metal containing aluminum as a main component and then hot forged.
When forging is performed at a temperature lower than the melting point, adhesion with other component particles is not completed and the density is reduced. In this case, the heating
It is desirable to use a method capable of heating the inside at high speed and uniformly. For example, there is an electromagnetic induction heating method or a plasma heating method. By adopting such a heating method, both quality and productivity can be satisfied. In order to prevent the above-described interfacial reaction between Al and diamond from progressing, the shorter the holding time at the maximum temperature, the better. The reason is,
At the time of heating before forging, the surface of a metal particle mainly composed of aluminum is usually covered with a thin film made of aluminum oxide, and the film suppresses an interfacial reaction with diamond. However, at the time of forging, a high pressure is applied, so that the film is instantaneously broken, and the molten aluminum adheres to the diamond, so that the reaction between the two easily proceeds more quickly. The heating time before forging is not more than 15 minutes as long as the temperature is uniform. Forging is desirably performed quickly and in a short time in a preheated mold in a state where a metal mainly composed of aluminum is molten. The standard of the preheating temperature of the mold is usually 200 to 5
Preferably, the temperature is set to 00 ° C. If the temperature is lower than the lower limit of the temperature range, the molten metal may be too cold and complexation and densification may not proceed. If the temperature exceeds the upper limit temperature, the effect may not be improved. It is particularly desirable to use a material such as a cemented carbide for the purpose of extending the life of the mold.

Forging is performed in the shortest possible time for the above-mentioned reason. It is desirable that the pressurization time be within one second. For example, if a friction press is used, usually 0.1
Densification and compounding can be achieved almost in seconds. The forging pressure is preferably at least 1 ton / cm ² .
If the pressure is less than this, the oxide film on the aluminum surface is not sufficiently broken, and the adhesion to the diamond particles tends to be insufficient. As a result, the aluminum may not uniformly cover the particle surfaces of SiC or diamond. As a result, some holes remain, and the thermal conductivity tends to decrease. Although it depends on the shape of the molded body to be forged and the material of the mold, a more preferable pressure is 5 ton / cm ² or more. The upper limit is 9
ton / cm ² .

[0029]

(Example 1) The average particle size is 50 μm, and the crystal type is I.
b type diamond powder (raw material 1), average particle size is 30μ
An aluminum alloy powder containing 10% by weight of Si and 0.4% by weight of Mg (raw material 2) and an aluminum powder having a mean particle size of 30 μm and a purity of 99% (raw material 3) were prepared. These powders were weighed out at the ratios shown in the column of "blending amount" in Table 1 and mixed by a dry ball mill. Note that "A" in the table
"1 alloy" and "pure Al" are raw materials 2 and 3, respectively. The mixed powder was vacuum-dried, pressurized at a low pressure, and then classified into a granular powder by a pressure granulation method of classifying the powder. This powder is pressed at a pressure of 8 ton / cm ^{2 to} a diameter of 100
After being dry-formed into a shape having a thickness of 10 mm and a thickness of 10 mm, this was placed in an induction heating furnace, heated at a heating rate of 600 ° C./min, and heated at a temperature in the range of 600 to 850 ° C.
Hold for 2 seconds. Next, each sample was immediately placed in a die steel die preheated to 450 ° C., which was placed in a friction press hot forging apparatus, and 8 ton / cm ^2.
And hot forging. Samples 10 to 13 in Table 1 were obtained by changing only the preheating holding temperature, and samples 14 to 17 were obtained by changing the forging pressure.

As comparative examples, test pieces of the same shape were prepared by the infiltration method or the hot press method with the composition shown in Table 2. Samples 19 to 22 were prepared by mixing and molding a diamond-Al powder to which the raw material of the second component was added in an amount of 10% by weight in the same manner as described above. It was placed in contact. Then 85
The temperature was raised to 0 ° C. and maintained for 4 hours (14400 seconds), and the melt of the second component was infiltrated into the voids of the molded body to obtain an infiltrated body having the component composition ratio shown in the same table. Sample 23 was prepared by placing the same molded body as that of Sample 3 of the present invention in an alumina mold.
In a nitrogen atmosphere, a pressure of 1 ton / cm ² at 850 ° C.
Sintering was performed for 0 minute (3600 seconds).

Tables 1 and 2 show the evaluation results of each sample prepared by the above procedure. The relative density is a ratio of the measured density confirmed by the underwater method to the theoretical density of the same composition. The interface layer in the table is a layer made of aluminum carbide formed at the interface between the diamond particles and the second component particles, and the presence or absence and the thickness of the layer were confirmed by a transmission electron microscope. The thermal conductivity was confirmed by a laser flash method, and the coefficient of thermal expansion was confirmed by a differential transformer type thermal expansion measuring device.

[0032]

[Table 1]

[0033]

[Table 2]

The following can be understood from the above results. According to the hot forging method of the present invention, a diamond-aluminum-based composite material which is denser than conventional infiltration methods and hot press methods and has remarkably high thermal conductivity can be obtained. This is because aluminum carbide having low thermal conductivity is hardly generated at the interface between the diamond particles and the second component particles containing aluminum as a main component, and the interface between both is rapidly pressed with a high pressure, so that they are sufficiently adhered to each other. Because.

Example 2 The average particle size was 50 μm and the crystal type was
IIa type diamond powder (raw material 5), average particle size 40μ
m, SiC powder having a crystal type of 6H (raw material 6) and powders of the second components of raw materials 3 and 4 used in Example 1 were prepared. These powders were weighed at the ratios shown in the column of "Blending Amount" in Table 3 and mixed and molded in the same procedure as in Example 1. Thereafter, this was placed in an induction heating furnace, heated at a heating rate of 600 ° C./min, and kept at a temperature in the range of 600 to 850 ° C. shown in Table 2 for 10 seconds. Next, each sample was immediately put into a die steel mold preheated to 450 ° C., which was placed in a hot forging device of a friction press system, and 8 tonnes were prepared.
/ Cm ^{2 at} a pressure of 10 seconds for hot forging. Samples 12 to 14 in Table 3 were obtained by changing only the preheating holding temperature, and samples 15 to 19 were obtained by changing the forging pressure.

As comparative examples, test pieces having the same shape were prepared by the infiltration method or the hot press method with the composition shown in Table 4. Samples 20 to 23 were prepared by mixing and compacting a diamond-Al-based powder to which 10% by weight of the raw material of the second component was added in the same manner as described above, and placing the molded product and the same infiltrant of the second component as the compounding raw material in a nitrogen atmosphere furnace. It was placed in contact. Then 85
The temperature was raised to 0 ° C. and maintained for 4 hours (14400 seconds), and the melt of the second component was infiltrated into the voids of the molded body to obtain an infiltrated body having the component composition ratio shown in the same table. Sample 24 was prepared by placing the same molded body as that of the present invention sample 4 in an alumina mold,
In a nitrogen atmosphere, a pressure of 1 ton / cm ² at 850 ° C.
Sintering was performed for 0 minute (3600 seconds). Each sample produced by the above procedure was evaluated in the same manner as in Example 1, and the results are shown in Tables 3 and 4.

[0037]

[Table 3]

[0038]

[Table 4]

The following can be understood from the above results. According to the hot forging method of the present invention, a diamond that is denser than the conventional infiltration method or hot pressing method and has a part of diamond having much higher thermal conductivity replaced with SiC.
An aluminum-based composite material is obtained. This is because aluminum carbide having low thermal conductivity is hardly formed at the interface between diamond particles or SiC particles and the second component particles containing aluminum as a main component, and both interfaces are rapidly pressurized at a high pressure. This is because it adheres to.

(Example 3) The diamond-aluminum-based composite materials obtained by the same method as the sample numbers 3 to 5 in Table 1 and the sample numbers 5 to 7 in Table 3 of the above-described example were each 50 pieces long. 200mm in width, 200mm in width, 3m in thickness
The substrate was finished to a shape of m. This was mounted on a power module as schematically shown in FIG. 2 as a heat radiating board, and a temperature cycle test was performed including each mounting step. In the present embodiment, a module was used in which six Si semiconductor elements were mounted via the first ceramic substrate.

Since the first substrate cannot be directly soldered to the second substrate prior to mounting, an electroless nickel plating layer having an average thickness of 5 μm and an average thickness of 3 μm
An electrolytic nickel plating layer was formed. Each of the four specimens was a 5 mm diameter hemispherical Ag-
A copper wire having a diameter of 1 mm was attached in a direction perpendicular to the plating surface by Sn-based solder. The substrate body of this specimen was fixed to a jig, a copper wire was grasped and pulled in a direction perpendicular to the plating surface, and the adhesion strength of the plating layer to the substrate was confirmed. As a result, none of the plating layers of any of the substrates was peeled off even with a tensile force of 1 kg / mm ² or more. Also, 10 samples were taken out of another sample on which the plating layer was formed, and held at −60 ° C. for 30 minutes.
A heat cycle test was performed by repeating 1000 cycles of raising and lowering the temperature for 30 minutes at 50 ° C., and after the test, the same adhesion strength as above was confirmed. Obtained. From the above results, it was found that the adhesion of the plating to the substrate made of the composite material of the present invention was at a level having no practical problem.

Next, as a first ceramic substrate mounted on the second substrate, a thermal conductivity of 150 W / m · K,
Thermal expansion coefficient 4.5 × 10 ^-6 / ° C, three-point bending strength 450
A substrate made of aluminum nitride ceramics of MPa, thermal conductivity of 120 W / m · K, thermal expansion coefficient of 3.7 ×
10 ^-6 / ° C., first a substrate formed with two copper circuits of silicon nitride ceramic substrate B of 3-point bending strength 1300 MPa, were prepared by 18 each. Each of these substrates has a length of 90 mm, a width of 60 mm, and a thickness of 1 m.
m. These substrates were arranged at equal intervals in two rows and three columns on a 200 mm square main surface of the second substrate, and were fixed on the surface of the same substrate on which the nickel plating layer was formed by Ag-Sn solder. Next, the back surface of the second substrate of the assembly and the water-cooled jacket were fixed with bolts closed by applying a silicone oil compound to the contact surface thereof. In this case, the mounting holes of the first substrate were formed by irradiating a carbon dioxide gas laser to the prepared holes previously formed in the four corners at the material stage, and expanding the holes to a diameter of 3 mm. This processing is performed using other ceramic materials, Cu-W, Cu
-Higher accuracy and higher speed than in the case of Mo. This tendency was particularly remarkable as the thermal conductivity increased.

From each of these test pieces, the first substrate was selected from 15 each of A and B, and a heat cycle test was performed for 2,000 cycles under the same single cycle conditions as described above. The change in output was confirmed. As a result, the output of all modules did not decrease until 1000 cycles, which is considered to be practically no problem.

From the above results, the diamond of the present invention
It can be seen that the power module using the first substrate made of the aluminum-based composite material has a practically acceptable level. The thermal conductivity is 170W / m · K separately.
These samples have lower power and lower heat than this type of module.
(Cycle) Mounting and evaluation as a heat dissipation board on a semiconductor device mounting device such as a personal computer with a high load capacity, but no problem in reliability and practical performance.

[0045]

As described in detail above, according to the present invention, the high heat conductivity of diamond is fully utilized by the hot forging, so that it has a high heat dissipation and a low coefficient of thermal expansion. A material for a semiconductor device can be provided. According to the present invention, at least 273 W / m · K or more, typically 50 or more, over a wide range of the amount of diamond or SiC.
A material having a high thermal conductivity exceeding 0 W / m · K can be obtained, and is useful as a heat dissipation substrate for various semiconductor devices. Especially 5
Those having a power of 00 W / m · K or more can also be used for extremely large capacity power modules.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the amount of diamond and the thermal conductivity of the composite material of the present invention.

FIG. 2 is a diagram schematically showing a semiconductor device (power module) using a material of the present invention for a substrate.

[Explanation of symbols]

 1: a first substrate made of a silicon carbide composite material 2: a second substrate 3: a semiconductor element 4: a heat dissipation structure

Claims (8)

[Claims] 1. A diamond-aluminum composite material containing diamond particles as a first component and a metal containing aluminum as a main component as a second component, wherein the composite material has a thermal conductivity at 25 ° C. of zW / m. -K, when the content of the diamond particles is x% by weight, at 5 ≦ x, −
0.0029x ² + 0.141x + 281.08 ≦ z ≦
0.2239x ² -12.017x + 593.93 diamond satisfy the relationship of - aluminum-based composite material. 2. The method according to claim 1, further comprising a third component comprising silicon carbide particles in addition to the first component and the second component, wherein a total amount of the first component and the third component is 30 to 80% by weight. The diamond-aluminum composite material according to claim 1, wherein the content of the two components is in the range of 20 to 70% by weight. 3. The thermal conductivity z at 25 ° C. is 10 ≦ x
At −0.0074 × ² + 1.162 × + 29
1.18 ≦ z ≦ 0.2239x2-12.017x + 5
The diamond-aluminum composite material according to claim 1 or 2, which satisfies a relationship of 93.93. 4. The thermal conductivity z at 25 ° C. is 30 ≦ x
At −0.0136 × ² + 5.0264 × + 24
6.19 ≦ z ≦ 0.2239x ² -12.017x + 5
The diamond-aluminum composite material according to claim 1 or 2, which satisfies a relationship of 93.93. 5. A semiconductor device using the diamond-aluminum composite material according to claim 1. 6. A method for producing a diamond-aluminum composite material containing diamond particles as a first component and a metal mainly composed of aluminum as a second component, wherein a raw material containing the first component and the second component is prepared. Step 1 of performing
Step 2 of mixing the raw materials so that the amount of the first component is 5% by weight or more to form a mixture; Step 3 of molding the mixture to form a molded body; Preheating at a temperature of 4 ° C. and forging into a forged body. 7. The step 1 is a step of preparing a raw material of a third component composed of silicon carbide particles in addition to the first component and the second component. Is 2
0 to 70% by weight, and the total amount of the first and third components is 30 to 8
The method for producing a diamond-aluminum-based composite material according to claim 6, which is a step of mixing the mixture so that the amount becomes 0% by weight to form a mixture. 8. The raw material of the first component is Ib type or II type.
The method for producing a diamond-aluminum-based composite material according to claim 6 or 7, which is a diamond containing a-type crystal particles.