JP2000297301A - Silicon carbide-based composite material, powder thereof, and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al-SiC-based silicon carbide composite material having a high thermal conductivity, which is useful for a heat dissipation substrate, particularly for a semiconductor device. SOLUTION: This is a powder of a silicon carbide-based composite material containing a metal mainly composed of aluminum as a first component and particles mainly composed of silicon carbide as a second component, and has an average particle diameter of 5 to 100 μm. And the individual particles have an average particle size of 5
A plurality of particles of the first component cover the particle surface of the second component having a particle size of μm or less, and the amount of silicon carbide in the entire powder is 10 to 85.
It is a powder of a silicon carbide-based composite material in weight%. A silicon carbide-based composite material having a relative density of 90% or more and a thermal conductivity of 220 W / m · K or more obtained using this powder. This powder is obtained by mechanically alloying the first and second component powders.

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, and more particularly to a silicon carbide composite material having high thermal conductivity used for a heat dissipating substrate of a semiconductor device. The present invention relates to a powder, a silicon carbide-based composite material obtained from the powder, and a semiconductor device using the same.

[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. Therefore, the basic structure is usually 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 should be at least 200 W at room temperature.
/ M · K or more and 10 × 10 ⁻⁶ / ° C. or less, especially 8 × 10
A material having a low thermal expansion coefficient of ^-6 / ° C or less is required.

[0004] In particular, among power devices having a large heat value in practical use, the temperature of the heat radiation 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, not only its dimensional accuracy at the time of mounting but also its lowering at a high temperature is required. 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.

For such a substrate, a substrate made of, for example, a Cu-W or Cu-Mo composite alloy has been used. These substrates have a problem that the cost is high and the weight is large because the raw material is expensive. 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. In addition, pure Al, S which is usually commercially available
The density of iC alone is about 2.7 g / cm ³ ,
3.2 g / cm ³ , thermal conductivity 240 W
/ M · K, up to about 200 to 300 W / 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. Also pure Si
The thermal expansion coefficients of C alone and Al alone are 4.2 × 10
^-6 / ° C. and 24 × 10 ^-6 / ° C., and by combining them, the thermal expansion coefficient can be controlled in a wide range. Therefore, this point is also advantageous.

The Al-SiC-based composite alloy and the method for producing the same are described in (1) JP-A-1-501489, (2) JP-A-2-343729, and (3) JP-A-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 have disclosed in Japanese Patent Application No. Hei 9-136164 (5) an aluminum-silicon carbide composite material obtained by (5) 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% by weight of particulate SiC powder and Al powder, it contains 99% or more of nitrogen and has an oxygen concentration of 20% or more.
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.

[0009]

The composite material described above is used as a substrate requiring a large amount of heat radiation, particularly a heat radiation substrate having a relatively large practical size and a large amount of heat radiation, such as a substrate for a semiconductor power device. In order to do so, there remain some issues to be solved as described below. For example, in the method for producing an Al-SiC-based composite material described in the above (1), a casting method in which an Al melt is poured into a mold, and the SiC particles are dispersed and solidified. Therefore, the density difference between Al and SiC causes segregation of SiC particles in the compact during cooling, and the composition of the solidified body tends to be non-uniform. Therefore, it is inevitable that the surface of the solidified body is covered with a coating layer made of Al or an Al alloy (hereinafter, this layer is also referred to as an Al coating layer). Usually, the thickness of the coating layer varies considerably depending on the location on the surface of the solidified body. Further, since there is a considerable difference in the thermal expansion coefficient between the surface portion of the solidified body made of the coating layer and the inside thereof, when heat is transmitted to the interface between them, thermal stress is generated there. Therefore, if this material is used as a heat dissipation board for mounting semiconductor devices while leaving this coating layer, the substrate will be warped or deformed by the generated thermal stress, and as a result, cracks will occur between the semiconductor device and peripheral members and the substrate. Or a semiconductor element or a peripheral member is deformed or broken. Therefore, it is necessary to completely remove this coating layer in advance.
In addition, since the thickness of the coating layer varies as described above, the removal is processing of a portion where a soft ductile Al-based phase and a highly rigid SiC-based phase coexist.
Therefore, it becomes difficult to process.

In the above-mentioned methods (2) and (3) for producing an Al—SiC composite material, Al is infiltrated into the voids of the porous SiC material. In this case, the melting A which is generated during the casting of steel
It is necessary to obtain a dense composite alloy by preventing shrinkage cavities of 1 and completely filling Al in the voids of SiC. For this reason, usually excess Al is disposed as an infiltrant on the outer periphery of the porous SiC body. After the infiltration, the excess Al is eluted and fixed on the outer periphery of the infiltrated body, and it takes a lot of trouble to remove it. In addition, a mixed powder containing Al and SiC as main components is previously molded and sintered.
In the method described in (5), when the sintering is performed at a temperature exceeding the melting point of Al, the same phenomenon occurs, albeit mildly.

Therefore, in order to prevent such elution and fixation of Al on the outer periphery, as described in (6) above,
Before infiltration, a thin layer made of a mixture of the anti-elution agent and an infiltration accelerator that promotes the infiltration is also applied and formed on the outer periphery of the porous SiC body. However, applying these layers and removing them after infiltration is troublesome.

In the pressure infiltration method (3), a porous SiC body is placed in a mold that can be uniaxially pressed, and Al or an Al alloy is placed on top of the porous body. The step of uniaxially applying the pressure from the outside and forcibly filling the SiC porous body is performed. In this case, finally, the infiltrated body is gradually cooled from the lower part with a temperature gradient. At this time, since the difference in thermal expansion coefficient between the SiC skeleton portion inside the infiltration body and the portion filled with Al is large, Al is pulled into the infiltration body during cooling and Al is not infiltrated (the above-mentioned shrinkage cavity). (Equivalent to). Therefore, a complicated control mechanism that can simultaneously and accurately control the temperature gradient at the time of cooling and the program of pressurization and heating is required. The device is therefore quite expensive.

Further, the method using hot pressing in a mold described in the above (4) has problems in production and quality as described below. For example, if a continuous type hot press device is used, a vacuum atmosphere and a temperature of A
In order to increase the melting point to 1 or more, it is necessary to suppress the outflow of the melt out of the mold. Therefore, in order to suppress the variation of the component amount and obtain a target having a uniform composition, an extremely expensive manufacturing apparatus is required. On the other hand, when the apparatus is of a batch type, the outflow of the melt out of the mold can be somewhat suppressed as compared with the continuous type. However, on the other hand, a series of steps of loading the molded body into the mold, holding and cooling at a predetermined temperature program are intermittently repeated,
This method lacks productivity.

As described in detail above, the conventional Al-SiC
There are some quality and production issues in the production of composite materials. Therefore, an Al-SiC-based composite material has been used as one of the substrates requiring high heat dissipation, such as a semiconductor power module, despite its recent promising performance. Any satisfactory casting method, infiltration method, sintering method, hot pressing method or any combination of these methods has not been able to obtain a satisfactory original performance level. The following can be considered as one of the reasons. That is, the wettability between Al and SiC is improved to promote spontaneous infiltration of the Al melt between the SiC particles, or a minor component such as Si is added to Al to suppress generation of voids. Or Al containing these minor components as impurities in many cases. For this reason, a decrease in the thermal conductivity of the composite material was unavoidable due to the interposition of these auxiliary components. Therefore, in order to ensure excellent thermal conductivity, it is important to use pure Al powder as much as possible and to ensure the wettability between the powder and the surface of the SiC particles.

In general, the thermal conductivity of a substance is a function of the density, specific heat, and thermal diffusivity of the substance as shown in the following equation. Thermal conductivity = Density x Specific heat x Thermal diffusivity Formula (1) Here, in the case of a composite material, the specific heat is determined by the composition ratio of the components. Therefore, if the composition is the same, it is necessary to increase the density and the thermal diffusivity in order to improve the thermal conductivity. In the above-mentioned conventional Al-SiC-based composite material, even if its density is 99% or more, its thermal conductivity is about 200 W / m · K.
In particular, it is necessary to improve the thermal diffusivity.

It is considered that the thermal diffusivity of the Al-SiC-based composite material is determined by the thermal diffusivity of Al and SiC and the state of adhesion between the two phases. The degree of adhesion at the interface between the two phases basically improves as the density increases. Therefore, as one direction to improve the thermal diffusivity of the Al-SiC-based composite material, it is important to ensure the wettability of both components while maintaining the purity of both components.

In order to solve the above-mentioned conventional problems, the present inventors have repeatedly studied with an emphasis on improving the thermal conductivity particularly in a composition region having a large amount of SiC. As a result, in Japanese Patent Application No. 10-260003, it has been expected that this problem can be overcome by reducing the amount of defects and impurities in SiC particles. However, in this method, in order to secure the high thermal conductivity, A having a relatively small amount of surface oxygen is used.
It is necessary to prepare 1 powder and high-purity SiC powder in advance, and the preparation thereof is troublesome. Further, since the purity of both components is high, the surface of the Al powder is particularly easily oxidized. Therefore, in order to ensure wettability during firing, high pressure is usually applied during molding to break the oxide film on the surface,
It is necessary to sufficiently adhere both component particles. Therefore, the mold is quickly consumed by the SiC powder. Therefore, this method can provide a material having excellent heat conductivity, but requires means with higher productivity.

On the other hand, when a commercially available Al powder having a large surface oxygen content is used, the raw material cost is reduced. However, even in that case, Si
In order to ensure the wettability with the C powder and to precisely combine the two, it is necessary to break the oxide film on the surface in advance.
For this reason, it is necessary to mold at a higher pressure than the above method, and the consumption of the mold is still a problem. Therefore, the present inventors have proposed a manufacturing method in which a heat treatment is added for deoxidizing a powder compact mainly containing Al and compaction can be performed at a relatively low pressure in Japanese Patent Application No. 10-369300. However, this method has a problem that voids remain due to insufficient wetting between the two components inside the molded body, and the originally high thermal conductivity cannot be obtained.

As described in the above (7) and (8), if the method is pressure sintering under hot pressure, it is possible to obtain a dense and highly heat-conductive material. However, these methods lack productivity. Therefore, Si
In the composition range where the C content is 50% by weight or more, a material having a high thermal conductivity exceeding 200 W / m · K has not yet been obtained by inexpensive firing under normal pressure.

[0020]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to overcome the above-mentioned problems in quality and production of the conventional silicon carbide composite material and to provide a material having a high thermal conductivity exceeding 200 W / m · K. Is provided at low cost by firing under normal pressure.

That is, the powder of the silicon carbide-based composite material provided by the present invention is a powder containing a metal containing aluminum as a main component as a first component and particles containing silicon carbide as a main component as a second component. The average particle size is 5 to 100 μm, and the individual particles have a plurality of particles of the first component covering the particle surface of the second component having an average particle size of 5 μm or less. The amount is from 10 to 85% by weight.

The silicon carbide composite material of the present invention is a material obtained by using the above powder, having a relative density of 90% or more and a thermal conductivity at room temperature of 220 W / m · K or more.
The present invention also includes a semiconductor device using the silicon carbide composite material.

The silicon carbide-based composite material powder according to the present invention is preferably a silicon carbide powder having an average particle diameter of 10 to 200 μm as a first component, and a metal powder containing aluminum as a main component as 15 to 90% by weight as a first component. It is manufactured by a method including a step 1 of preparing 10 to 85% by weight and a step 2 of mechanically alloying these powders in a non-oxidizing atmosphere until the average particle diameter of the second component becomes 5 μm or less. The method for producing a powder of the present invention also includes means for performing the mechanical alloying in Step 2 at an acceleration of 10 G or more.

The silicon carbide-based composite material of the present invention is formed into a compact by molding the powder obtained by the above-described procedure into a molded body, and the sintered body is sintered in a non-oxidizing atmosphere to form a sintered body. Step 4
And a production method comprising:

The firing temperature in the above step 4 is 500
The present invention also includes a method in which the temperature is higher than or equal to ° C. and a method in which the temperature is higher than the melting point of a metal containing aluminum as a main component. Further, in the production method of the present invention, the molding pressure in the above step 3 is 6 t.
on / cm ² or more, and the molding is warm,
In particular, a method performed at 100 to 200 ° C is also included.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The powder of a silicon carbide composite material provided by the present invention and the composite material obtained by using the same are those in which the first component is composed of a metal containing aluminum as a main component (hereinafter referred to as Al-SiC). Based composite material or simply A
1-SiC-based and Al-based). The present invention focuses on this material and has been made to improve the thermal conductivity of a heat dissipation substrate (heat sink), particularly a heat dissipation substrate for a semiconductor device.

The average particle size of the powder of the silicon carbide composite material provided by the present invention is 5 to 100 μm. The individual particles are composite particles in which a plurality of particles of the first component cover the surface of the second component SiC particles having an average particle size of 5 μm or less. The amount of SiC particles in the whole powder of the present invention is 10 to 85% by weight. As described below, this powder is obtained by mechanically alloying a mixture of both components (Mech alloy).
(animal Alloying, hereinafter also referred to as MA)
It is obtained by doing. The reason why the average particle size of the mechanically alloyed and composited powder is within the above range is that the molding density does not increase below the lower limit, the amount of aluminum increases above the upper limit, and the mechanically alloyed container becomes This is because the powder adheres strongly and it becomes difficult to recover the powder, and as a result, the recovery rate of the powder decreases.
The preferred average particle size is 50 to 100 μm. The reason why the average particle diameter of the silicon carbide particles incorporated therein is 5 μm or less is that if the average particle diameter exceeds 5 μm, the density of the compact does not sufficiently increase and the thermal conductivity decreases. Preferably 3 μm
It is as follows. 10 to 85% by weight of silicon carbide in powder
If the first component is melted when the molded body is fired below the lower limit, it is difficult to maintain its shape. On the other hand, if it exceeds the upper limit, the amount of the melt of the first component decreases, and the densification during firing does not proceed sufficiently.

The silicon carbide-based composite material of the present invention is a material obtained by using the above powder, having a relative density of 90% or more and a thermal conductivity at room temperature of 220 W / m · K or more.
When the relative density is less than 90%, the thermal conductivity sharply decreases.
Preferably it is 94% or more. The relative density is the ratio of the measured density to the theoretical density calculated from the composition by the compound rule.

The silicon carbide-based composite material powder of the present invention comprises 15 to 90% by weight of a metal powder mainly composed of aluminum or copper as a first component and silicon carbide having an average particle diameter of 10 to 200 μm as a second component. It is manufactured by a method including a step 1 of preparing powders 10 to 85% by weight and a step 2 of mechanically alloying these powders in a non-oxidizing atmosphere until the average particle size of the second component becomes 5 μm or less. . The reason why the average particle diameter of the second component before the mechanical alloying is set in the above range is that if the average particle diameter is less than the lower limit, the amount of oxygen on the surface of the silicon carbide particles increases, and the oxygen reacts with the surface of the aluminum particles to form an oxide of aluminum. Is generated, and the chemical adhesion between the two components due to mechanical alloying described later is impaired. If the upper limit is exceeded, the silicon carbide is not pulverized to fine particles, and the compounding of both components becomes insufficient. As a result, in any case, a dense and excellent heat conductive material cannot be obtained.

The mechanical alloying atmosphere is performed in a non-oxidizing atmosphere in order to avoid oxidation of the first component. In this case, a normal ball mill may be used, but if a planetary ball mill having a large crushing energy is used, MA can be performed in a short time. For example, both component powders and balls of a grinding medium are filled into pots of these apparatuses, and the pots are revolved around themselves and mixed and pulverized. It is preferable that the rotational acceleration of the pot be 10 G or more. If it is less than 10 G, the crushing energy is not so different from that of a normal ball mill, the crushing efficiency is reduced, and the crushing may take too much time. The higher the rotational acceleration is, the higher the crushing efficiency is, but in the present invention, it is at most about 150G. Beyond that, the grinding energy becomes SiC
Is not consumed in the milling of the particles, but rather distorts the particles, resulting in a decrease in thermal conductivity. The material of the pot lining and the crushing medium may be a material having excellent wear resistance, but it is preferable to use, for example, a SiC-based material which is a main component of the composite material, or a material coated therewith. .

In the mechanical alloying process of the present invention, the SiC particles having an average particle diameter of 10 to 200 μm become finer as they proceed. On the other hand, the particles of the first component, whose initial average particle diameter is usually several tens to several hundreds of micrometers, cover around the SiC particles that have been plastically deformed and miniaturized. When this is repeated, as shown schematically in FIG. 1, secondary composite particles are formed in which the entire surface of the fine SiC particles is covered by a large number of particles of the first component. Although the oxide layer is formed on the initial surface of the first component particles as described above, the layer is broken by MA to expose a reactive surface composed of pure first component metal. On the other hand, the surface of the broken SiC particle also becomes a reactive surface. These active surfaces come into direct contact with each other under the repetitive load of high energy, and a solid-phase reaction occurs at their interface, resulting in a chemically bonded state.

The size of each atomized SiC particle is as small as 1 μm or less, and further down to about 50 nm in the case of a small one. MA is performed until the average particle size becomes 5 μm or less. If it exceeds 5 μm, the compressibility of the composited particles is reduced, and the rate of increase in the molding density with an increase in pressure is undesirably reduced. This is because when the first component undergoes plastic deformation due to the pressure during molding, the smaller the SiC particles, the easier it is to move in response to the deformation. In this way, the composited particles themselves have SiC embedded therein.
Since it is easily deformed without being hindered by particles, molding can be performed even at a relatively low pressure. FIG. 2 schematically shows this state in comparison with a mixed powder of simple mixing without performing MA. (A) of the figure shows the case of the powder not subjected to MA, and (b) shows the case of the powder of the present invention subjected to MA.
With conventional powder, if the first component is plastically deformed during molding,
The adhesion of the particles progresses only at the portion where the deformation reaches, and the first component cannot cover the entire surface of the large SiC particle that does not follow the deformation, and the first component does not take in the same. As a result, voids remain in some parts of the surface of the SiC particles after molding. On the other hand, in the powder of the present invention, since the SiC particles are atomized, the SiC particles rearrange in accordance with the flow of the plastic deformation of the first component. For this reason, even if molded at the same pressure, the compressibility is significantly different as shown in the figure. Heating the molded article of the present invention in which both components adhere at a wide interface at a temperature equal to or higher than the melting point of the first component,
The surface of the melt of the first component and the surface of the SiC particles are easily wetted even under normal pressure, and voids at the interface between them are greatly reduced. As a result, even with the same composition, the thermal conductivity increases dramatically.

The silicon carbide-based composite material of the present invention is obtained by molding the powder obtained by the above procedure into a molded body in step 3; and firing the molded body in a non-oxidizing atmosphere to form a sintered body. Step 4
And a production method comprising: The molding method is not limited, but dry powder molding is preferable in terms of production efficiency. The mold at the time of molding may be a wear-resistant material. For example, it is desirable that a surface that comes into contact with the powder be coated with a hard coating such as SiC, diamond, and diamond-like carbon.
The molding pressure is usually desirably 6 ton / cm ² or more.
It should be noted that an increase in the molding density cannot be expected even when a pressure of 10 ton / cm ² or more is applied. Promotes plastic deformation of the first component,
In order to increase the molding density, it is desirable to perform the warming. In the case of pure aluminum, the upper limit is about 150 ° C., but the preferred forming temperature is 100 to 200 ° C. When an alloy powder containing a small amount of a minor component such as Si or Mg in aluminum is used, the temperature may be raised to about 300 ° C. in order to facilitate its plastic deformation.

The firing temperature in step 4 of the present invention is usually desirably equal to or higher than the melting point of the first component metal. However, sintering is possible even at a temperature lower than the melting point of the same metal, and a material having relatively high thermal conductivity can be obtained. The reason is that the interface between the two components in the composite particles in the molded article is chemically bonded as described above, so that the contact between the two components is maintained to the extent that heat conduction is not hindered. is there. This effect is particularly apparent when the amount of SiC particles is 50%.
It becomes remarkable in the composition range of not more than% by weight. Incidentally, the lower limit of the firing temperature is 500 ° C. However, the melting point of the first component metal is usually desirable. In particular, the temperature is desirably up to 750 ° C. This is because if the temperature is exceeded, aluminum carbide (Al ₄ C ₃ ) having low thermal conductivity is formed at the interface between aluminum and the SiC particles, and the thermal conductivity tends to decrease. The baking atmosphere may be a non-oxidizing gas atmosphere such as nitrogen, but baking is possible even in a vacuum. In addition, the sintering may be usually performed under normal pressure.
Under a pressurized condition such as IP, densification becomes easier to proceed, and more excellent thermal conductivity can be obtained.

As the raw material of the first component mainly composed of aluminum, a commercially available one may be used. However, in order not to lower the thermal conductivity of the composite material, it is preferable to use a high-purity main component of the composite material, except when using a powder to which an alloy element is added. For example, it is desirable to use 99% or more. The raw material of the first component used in the present invention may be in any form such as a lump, a powder, or the like, but usually a powder is used. Except for the case where an alloying element is added, when a pure metal is used as the impurity species interposed in the raw material powder, a transition metal element which is easily dissolved in the main component metal of the first component, particularly a Group 8a element, is used. It is desirable that the number of components including the components is as small as possible. Furthermore, in order to further increase the purity of the main component of the first component metal powder, it is necessary to prepare a powder whose purity has been adjusted by a melt spraying method or a physical or chemical treatment method among commercially available powders.

[0036]

EXAMPLE 1 As a second component, "Si" in Table 1 was composed of 6H type crystal particles.
SiC powders having various average particle diameters described in the column of “C raw material”, pure aluminum powder having an average particle diameter of 25 μm, and aluminum alloy powder containing 5% by weight of Si were prepared as first components. Each component powder was weighed in the amount shown in Table 1 and subjected to MA. The compounding amount of the SiC powder was the parts by weight described in the “SiC raw material” column of Table 1, and the compounding amount of the first component was the rest. The type of the first component powder is the “first component” in Table 1.
The powder type described in the column was used. These powders were put into a stainless steel pot of a planetary ball mill together with a stainless steel ball having a diameter of 3 mm, and mixed and pulverized at the rotational acceleration and time of the pot for each sample shown in Table 1 to form a composite. Powder. Further, only the powder of the sample 1 was mixed with a raw material powder having the compounding amount shown in Table 1 by a usual ball mill. Each of the produced powders was embedded in a resin, and the cross section was observed at a magnification of 3000 times with a scanning electron microscope. As a result, each powder was found to have a first component mainly composed of aluminum around the micronized SiC particles. The powder had a structure coated with a plurality of particles. The average particle size of the SiC particles contained in the powder and the average particle size of the composite powder were measured, and the results are shown in the “Composite powder” column of Table 1. The average particle diameter was a value obtained by taking a photograph of a 3000-fold rectangular visual field, measuring the lengths of all particles cut by two diagonal lines, and arithmetically averaging them.

Next, each of the powders was placed in a mold maintained at a temperature shown in the column of "Molding" in Table 1 and formed into a shape having a diameter of 35 mm and a thickness of 10 mm under the pressure shown in the table. Next, each of these sample powders was sintered under the conditions described in the “calcination” column of Table 1. Further, as for the powder of Sample 9, a sintered body in which only the firing temperature was 480 ° C. and 520 ° C. was manufactured under the same atmosphere and time. Sample 7 was found to have a composition that was difficult to commercialize due to its collapsed shape after firing. The relative densities of these sintered bodies, the thermal conductivity measured by the laser flash method, and the coefficient of thermal expansion measured by a working transformer type thermal elongation measuring apparatus are shown in the column of "Sintered body" in Table 1. The powder of sample 9 was
The relative densities of the samples sintered at 80 ° C. and 520 ° C. were 96.1% for the former and 97.5% for the latter. As a result, the thermal conductivity was 200 W / m · K for the former and 220 W / m · K for the latter.

[0038]

[Table 1]

The following becomes clear from the above results. That is, (1) the powder of the present invention in which the SiC particles are refined to 5 μm or less by performing MA and the periphery thereof is covered with particles of the first component containing aluminum as a main component is superior in compressibility as compared with a simple mixed powder. I have. Therefore, when molding is performed under the same pressure, a molded article having a higher molding density can be obtained. (2) The compact of this powder becomes a composite material having a higher thermal conductivity than that obtained by sintering a compact of a simple mixed powder. When the firing temperature is increased to 500 ° C. or higher, particularly to the temperature equal to or higher than the melting point of the first component, a composite material having a high thermal conductivity of 220 W / m · K or higher can be easily obtained. (3) The amount of SiC particles is 1
When sintering at a temperature higher than the melting point of the first component using less than 0% by weight of powder and more than 85% by weight of composite powder, the former cannot maintain its shape, and the latter has a relative density of less than 90%, and the thermal conductivity decreases. I do.

Example 2 Fifty sintered bodies obtained by the same manufacturing method as Samples 3, 4, 10, 14, and 18 of Example 1 were each 200 mm long and 200 m wide.
m and a thickness of 3 mm. This was mounted on a power module as schematically shown in FIG. 3 as a heat radiating substrate, and a temperature cycle test was performed including each mounting step. In FIG. 3, reference numeral 1 denotes a second heat radiation substrate made of the above-described composite material of the present invention, and 2 denotes a second heat radiation substrate disposed on the same substrate.
An electric insulating first substrate (not shown) made of ceramics on which a copper circuit is formed, 3 is a Si semiconductor device, and 4 is a heat dissipation structure disposed below the second heat dissipation substrate. The jacket is a water-cooled jacket in the present embodiment, but may also include air-cooled fins. It should be noted that wiring and the like around the semiconductor element are omitted in FIG. 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, 15 first substrates A and B were selected and subjected to a heat cycle test of 2,000 cycles under the same single cycle conditions as described above. The change in output was confirmed. As a result, all the modules continued the test up to 1000 cycles, which is considered to be no problem in practical use, and further up to 2000 cycles, but no decrease in output was observed. From the above results, it can be seen that the power module using the first substrate made of the silicon carbide-based composite material of the present invention has a practically acceptable level.

The material of the present invention was mounted and evaluated as a heat radiation board on a semiconductor device mounting device such as a personal computer having a low output and a low heat (cycle) load and a high capacity compared to this type of module. -There was no problem in practical performance.

[0045]

As described above in detail, according to the present invention, a powder mainly containing silicon carbide (SiC) particles and a powder mainly containing aluminum are subjected to mechanical alloying to form a powder having a particle size of 5 μm or less. By making the SiC particles finer to an average particle size and forming a composite powder around the particles covered by a plurality of particles of the first component, higher than conventional powders of the same composition simply mixed A compressible powder is obtained. By molding and sintering this powder,
An excellent silicon carbide composite material useful for an excellent semiconductor device having a relative density of 90% or more and a thermal conductivity of 220 W / m · K or more can be obtained. Therefore, the silicon carbide composite material of the present invention is useful as a heat-dissipating substrate on which a semiconductor element is mounted, particularly a highly reliable heat-dissipating substrate for a high-output power module.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a mechanical alloying process of the powder of the present invention.

FIG. 2 is a diagram comparing molding processes of a powder of the present invention and a conventional powder that is simply mixed, and schematically explaining the differences between the two.

FIG. 3 is a diagram schematically showing a semiconductor device (power module) using a material of the present invention for a substrate.

[Explanation of symbols]

 1. First substrate 2, second substrate 3, semiconductor element 4, heat dissipation structure made of silicon carbide composite material

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 32/00 C22C 32/00 Q H01L 23/373 H01L 23/36 M

Claims (12)

[Claims] A powder of a silicon carbide-based composite material containing a metal containing aluminum as a main component as a first component and particles containing silicon carbide as a main component as a second component. 100 μm, the individual particles having an average particle size of 5
A plurality of particles of the first component cover the particle surface of the second component having a particle size of μm or less, and the amount of silicon carbide in the entire powder is 10 to 85.
A powder of a silicon carbide-based composite material which is in weight%. 2. A silicon carbide-based composite material obtained by using the powder of the silicon carbide-based composite material and having a relative density of 90% or more and a thermal conductivity at room temperature of 220 W / m · K or more. 3. A semiconductor device using the silicon carbide composite material according to claim 2. 4. A method for producing a powder of a silicon carbide-based composite material comprising a metal having aluminum as a main component as a first component and particles having silicon carbide as a main component as a second component. Powder 15 of a metal mainly composed of aluminum
~ 90% by weight and an average particle size of 10-2 as a second component
A step 1 of preparing 10 to 85% by weight of silicon carbide powder of 00 μm and a step 2 of mechanically alloying these powders in a non-oxidizing atmosphere until the average particle size of the second component becomes 5 μm or less. A method for producing a powder of a silicon-based composite material. 5. The method for producing a powder of a silicon carbide composite material according to claim 4, wherein in the step 2, mechanical alloying is performed at an acceleration of 10 G or more. 6. A method for producing a silicon carbide composite material comprising a metal having aluminum as a main component as a first component and particles having silicon carbide as a main component as a second component, wherein aluminum is used as the first component. Metal powder 15 to 90 as main component
% By weight and an average particle size of 10 to 200 μm as the second component
Step 1 of preparing 10 to 85% by weight of silicon carbide powder
And 2) mechanically alloying these powders in a non-oxidizing atmosphere until the average particle size of the second component becomes 5 μm or less to obtain a powder of a silicon carbide composite material. And a step 4 of firing the compact in a non-oxidizing atmosphere to form a sintered body. 7. The method of manufacturing a silicon carbide composite material according to claim 6, wherein in the step 2, mechanical alloying is performed at an acceleration of 10 G or more. 8. The method for producing a silicon carbide composite material according to claim 6, wherein in step 4, the firing temperature is 500 ° C. or higher. 9. The method for producing a silicon carbide-based composite material according to claim 6, wherein the firing temperature is equal to or higher than the melting point of the first component. 10. The method for producing a silicon carbide-based composite material according to claim 6, wherein the step 3 is performed under a pressure of 6 ton / cm ² or more. 11. The method for producing a silicon carbide-based composite material according to claim 6, wherein the step 3 is performed during warm forming. 12. The molding temperature in the warm state is 100 to 100.
The method for producing a silicon carbide-based composite material according to claim 11, wherein the temperature is 200 ° C.