JP2001185665A - Radiating plate made of silicon carbide and metal composite material and board for module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiating plate capable of being suitably used as a board for a module for mounting a semiconductor element having a large heating amount, excellent durability for a temperature cycle due to substantially equal thermal expansion coefficient to that of an aluminum nitride board having sufficiently highly thermal conductivity. SOLUTION: The radiating plate comprises a silicon carbide and metal composite material impregnated with a metal in open pores existed in a porous texture constituted of a silicon carbide crystal. In this case, the mean grain size of the crystal is 20 μm or more, its porosity is 30% or less, its thermal conductivity is 100 W/m.K or more. The plate comprises 15 to 50 pts.wt. of metal to 100 pts.wt. of the silicon carbide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat radiating plate having excellent heat radiating characteristics, and a module substrate for mounting a semiconductor element having a large heat value, using the heat radiating plate.

[0002]

2. Description of the Related Art An insulating substrate and a heat sink are provided as a substrate on which a power semiconductor element such as an IGBT (insulated gate bipolar transistor) or an SIT (static induction transistor) which generates a large amount of heat during operation is mounted. In addition, a module substrate having excellent heat dissipation characteristics is used.

FIG. 5 is a cross-sectional view schematically showing a power module using this type of module substrate. In the power module 20, a conductor circuit 15 is formed on one main surface of the insulating substrate 12, and a semiconductor element 16 is mounted on a part of the conductor circuit 15, and the other conductor circuit 15 and the semiconductor element 16 Are connected by wire bonding using the wires 15a. An external terminal 19 is connected to one end of the conductor circuit 15 via a solder layer 18.

On the other hand, a metal layer 13 is formed on almost the entire bottom surface of the insulating substrate 12, and a heat sink 21 is joined to the metal layer 13 via a solder layer 14.

In the power module 20, a large amount of heat is generated in the semiconductor element 16 by an operation such as switching, and the heat is radiated to the outside through the insulating substrate 12, the metal layer 14, and the heat radiating plate 11. Therefore, the semiconductor element 16
Excessive temperature rise can be prevented.

Conventionally, the conductor circuit 15 and the metal layer 13
Is used as a material for forming the insulating substrate 12, while ceramic such as alumina is used as a material for forming the insulating substrate 12.

However, in the power module 20 using such a material, when subjected to a temperature cycle due to a process such as soldering of the semiconductor element 16 or heat generation of the semiconductor element 16 during use, heat of copper and ceramic is generated. There is a problem that cracks occur in the insulating substrate 12 due to thermal stress caused by the difference in expansion.

In order to solve such a problem, a power module using aluminum having a small deformation resistance as a metal for a conductor circuit and using an aluminum nitride substrate having an excellent thermal conductivity as an insulating substrate 12. Is being developed. In this power module, so-called AlSiC in which aluminum is impregnated in a silicon carbide porous body is used as heat sink 11.

In a power module using these materials, it is possible to prevent the insulating substrate 12 from cracking due to a difference in thermal expansion between the conductor circuit 15 and the insulating substrate 12. In addition, since the heat radiating plate 11 made of AlSiC has a coefficient of thermal expansion relatively close to that of aluminum nitride, cracks and the like are not easily formed at the joint between the insulating substrate 12 and the heat radiating plate 11. Furthermore, since the heat sink 11 has a high thermal conductivity, the heat sink and a substrate composed of an insulating substrate and the like are:
Excellent heat dissipation characteristics.

However, the thermal expansion coefficient of the conventional heat radiating plate 11 made of AlSiC is 6.7 × 10 ⁻⁶ (/
C.), the thermal expansion coefficient of the insulating substrate 12 made of aluminum nitride is about 4.5 × 10 ⁻⁶ (/ ° C.), and the heat expansion coefficient of the heat radiating plate 11 is about ^1.10 ° C.). Because it is five times larger, it is hard to say that the thermal expansion coefficients of both are the same,
Moreover, the heat conductivity of the heat sink 11 was not sufficient.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a sufficiently high thermal conductivity and a substantially equal thermal expansion coefficient with an aluminum nitride substrate. It is an object of the present invention to provide a heat sink that can be suitably used as a substrate for mounting a semiconductor element that generates a large amount of heat, and a module substrate using the heat sink.

[0012]

According to the heat sink made of the silicon carbide / metal composite of the present invention, open pores are present in a porous structure composed of silicon carbide crystals, and the open pores are impregnated with a metal. A heat sink comprising a silicon carbide / metal composite, wherein the silicon carbide crystal has an average particle diameter of 20 μm or more, a porosity of 30% or less, and a thermal conductivity of 100 W / m · K.
As described above, 15 to 50 parts by weight based on 100 parts by weight of silicon carbide
It is characterized by being impregnated with parts by weight of metal.

Further, the module substrate of the present invention comprises an insulating substrate having a conductor circuit formed on one main surface thereof, and a heat radiating plate joined to the other main surface of the insulating substrate via a metal layer. A module substrate for mounting a semiconductor element, wherein a heat sink made of the silicon carbide / metal composite is used as a heat sink. Hereinafter, the present invention will be described in detail.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a radiator plate (hereinafter, simply referred to as a radiator plate) comprising the silicon carbide / metal composite of the present invention will be described. In the silicon carbide / metal composite (hereinafter, also simply referred to as composite) constituting the heat sink of the present invention, open pores exist in a porous structure composed of silicon carbide crystals, and metal exists in the open pores. An impregnated composite, wherein the silicon carbide crystal has an average particle size of 20 μm or more, a porosity of 30% or less, a thermal conductivity of 100 W / m · K or more, and 15 wt. It is characterized by being impregnated with ５０50 parts by weight of metal.

In the above-described composite, the average particle size of the silicon carbide crystal is set to a relatively large value of 20 μm or more, so that the thermal conductivity is higher than in the prior art. This is because the efficiency of heat conduction inside the crystal is generally higher than the efficiency of heat conduction between crystals, so that the larger the average particle size, the higher the thermal conductivity. Further, in the composite of the present invention, sintering progresses, and as shown in the scanning electron micrograph (SEM photograph) of FIG. 2, the neck connection is increased, so that the thermal conductivity is further increased. . However, as shown in the SEM photograph of FIG. 3, when the sintering does not proceed, the neck connection does not proceed, so that the thermal conductivity does not increase.

The fact that the porosity of the porous structure is set to a small value of 30% or less also contributes to the improvement of the thermal conductivity. That is, as the porosity decreases, the voids in the porous structure decrease, so that heat is easily conducted. Further, the fact that the metal is impregnated with 15 to 50 parts by weight with respect to 100 parts by weight of silicon carbide also contributes to the improvement of the thermal conductivity.

As a result of the above-described composite, the composite has a large value of thermal conductivity of 100 W / m · K or more, and is less likely to have a temperature variation. The value of the thermal conductivity is preferably from 180 to 280 W / m · K, and more preferably from 200 to 260 W / m · K. In the composite, the above-described preferable thermal conductivity can be achieved by setting the porosity of the open pores, the particle size of the particles, and the like to more preferable ranges.

The average particle size of silicon carbide constituting the composite is preferably 20 to 100 μm, more preferably 30 to 90 μm, and most preferably 40 to 70 μm. If the average particle size is too large, the composite may be excessively densified. The porosity of the open pores of the silicon carbide is preferably 5 to 30%, more preferably 10 to 20%, and most preferably 10 to 20%.

The composite has an average particle diameter of 0.1 to 0.1.
It contains 10 to 50% by volume of fine silicon carbide crystals (hereinafter, referred to as fine crystals) of 1.0 μm, and has an average particle size of 25 to
150 μm coarse silicon carbide crystal (hereinafter referred to as coarse crystal)
Is preferably 50 to 90% by volume.

As described above, in the case of a composite containing fine crystals and coarse crystals in an appropriate ratio, the voids formed between the coarse crystals are filled with fine crystals as shown in the SEM photograph of FIG. It is easy to be in a state where the gap is formed, and the ratio of the substantial void is reduced. As a result, the thermal resistance of the composite becomes even smaller,
This is considered to have greatly contributed to the improvement of the thermal conductivity. On the other hand, as shown in the SEM photograph of FIG.
If there are no fine crystals around the coarse crystals, even if the neck coupling proceeds to some extent, the ratio of the voids increases, and the thermal conductivity does not improve much.

The average diameter of the fine crystals is 0.1 to 1.0 μm.
Is preferable, 0.2 to 0.9 μm is more preferable, and 0.
Most preferably, it is 3 to 0.7 μm.

If an attempt is made to reduce the average particle size of the fine crystals to an extremely small value, it is necessary to use expensive fine powder, which may lead to high boiling of the material cost. Conversely, if the average grain size of the fine crystals is too large, the voids formed between the coarse crystals cannot be filled, and the thermal resistance of the composite may not be sufficiently reduced.

In this composite, the fine crystals are 10 to 5
It is preferably contained at 0% by volume, more preferably 15 to 40% by volume, and more preferably 20 to 40% by volume.
Most preferably, it is included. If the content ratio of the fine crystals is too small, it becomes difficult to secure a sufficient amount of the fine crystals to fill the voids formed between the coarse crystals, and the thermal resistance of the composite cannot be reliably reduced. There is a risk. Conversely, if the content ratio of the fine crystals is too large, the amount of the fine crystals filling the voids becomes rather excessive, and the coarse crystals required to improve the thermal conductivity cannot be secured. Therefore, the thermal resistance of the composite may be rather increased.

In the above composite, the average grain size of the crude crystals is preferably 25 to 150 μm, more preferably 40 to 100 μm, and most preferably 60 to 80 μm. If an attempt is made to reduce the average particle size of the coarse crystals, the difference in particle size between the fine crystals and the fine crystals becomes small. As a result, the effect of reducing the thermal resistance by mixing the fine crystals and the coarse crystals may not be expected. Conversely, if the average grain size of the coarse crystals is too large, individual voids formed between the coarse crystals become large, so that even if there is a sufficient amount of fine crystals, the voids are sufficiently filled. It becomes difficult to do. Therefore, there is a possibility that the thermal resistance of the composite cannot be sufficiently reduced.

In the above composite, the crude crystals are 50 to 90
%, Preferably 60 to 85% by volume.
It is more preferably contained, and most preferably 60 to 80% by volume. When the content ratio of the coarse crystals is too small, the coarse crystals required to improve the thermal conductivity cannot be originally secured, and the thermal resistance of the composite may be rather increased. Conversely, when the content ratio of the coarse crystals is too large, the content ratio of the fine crystals becomes relatively small, and it becomes impossible to sufficiently fill the voids formed between the coarse crystals. Therefore, there is a possibility that the thermal resistance of the composite cannot be reliably reduced.

In the composite constituting the heat sink of the present invention, 15 to 50 parts by weight of metal is impregnated with respect to 100 parts by weight of silicon carbide. By performing the metal impregnation, the metal is filled in the open pores of the sintered body, and the metal becomes apparently dense, and as a result, the thermal conductivity and the strength are improved.

As the impregnating metal, metallic silicon is particularly preferred. Metallic silicon has a high thermal conductivity in itself, in addition to being a material that is well compatible with silicon carbide. Therefore, by filling metallic silicon into the open pores of the sintered body, it is possible to reliably achieve improvements in thermal conductivity and strength.

In this case, the metal silicon is silicon carbide 10
It is preferably impregnated with 15 to 45 parts by weight, more preferably with 15 to 39 parts by weight, based on 0 part by weight. If the impregnation amount is less than 15 parts by weight, the open pores cannot be sufficiently filled, and the thermal resistance of the composite may not be reduced reliably.
Conversely, if the impregnation amount exceeds 30 parts by weight, the ratio of the crystal part relatively decreases, and in some cases, the thermal conductivity may instead decrease.

Incidentally, other than metal silicon, for example,
When metal aluminum is selected, its impregnation amount is
It is preferably 20 to 50 parts by weight based on 100 parts by weight of silicon carbide. If the impregnation amount is outside the above range, the thermal conductivity may decrease and the coefficient of thermal expansion may increase.

Next, a method of manufacturing a heat sink made of such a composite will be described. The heat sink is manufactured through a material preparation step of mixing a fine powder with a coarse powder at a predetermined ratio, a molding step, a firing step, and a metal impregnation step.
The metal impregnation step may be performed before the firing step, or may be performed after the firing step.

In the material preparation step, the average particle size is 5
Α-type silicon carbide fine powder having an average particle size of 0.1 to 1.0 μm is added to α-type silicon carbide coarse powder of
100 parts by weight are mixed and uniformly mixed.

The average particle size of the coarse powder of α-type silicon carbide as a raw material is preferably 5 to 100 μm, more preferably 15 to 75 μm, and even more preferably 25 to 60 μm. Also, α
The average particle size of the fine silicon carbide powder is 0.1 to 1.0 μm
Is preferable, and 0.1 to 0.8 μm is more preferable.
Most preferably, it is 2 to 0.5 μm.

The amount of the fine powder relative to 100 parts by weight of the coarse powder is preferably 10 to 100 parts by weight, more preferably 15 to 65 parts by weight, and most preferably 20 to 60 parts by weight.

In this material preparation step, in addition to the above-mentioned silicon carbide powder, a molding binder such as polyvinyl alcohol and acrylic resin and a dispersing solvent such as alcohol, water and benzene are blended as required, and this is mixed with a vibration mill. After mixing by kneading using a kneader or the like,
Prepare raw material slurry.

The raw material slurry preferably further contains 1 to 10% by weight, more preferably 6 to 9% by weight, of an organic substance as a carbon source in terms of carbon weight. That is, the carbon derived from the organic substance adheres to the surface of the silicon carbide of the sintered body, so that the metal silicon and the carbon that have entered react with each other, and silicon carbide is newly generated there. Therefore, strong necking occurs there, thereby improving the thermal conductivity and strength (see FIG. 4).

Examples of the organic substance include phenolic resin, carbon black, acetylene black, pitch, tar and the like. Among them, phenolic resin is advantageous in that raw materials can be uniformly mixed when a ball mill is used.

In the forming step, silicon carbide granules are formed using the raw material slurry, and then formed into a predetermined shape using a mold or the like. As a method of granulating the silicon carbide powder, a conventionally known method such as a granulation method by spray drying (spray drying method) can be used. Further, the molding pressure is preferably ^{1.0~1.5t / cm 2, 1.1~1.4t / cm} 2 is more preferable. The density of the resulting molded article, 2.0 g / cm ³ or more preferably, 2.2~2.7g / cm ³ is more preferable.

In the firing step, the obtained molded body is
It is fired in a temperature range of 700 to 2400 ° C. to produce a porous body. The firing temperature is preferably from 2000 to 2400 ° C, more preferably from 200 to 2300 ° C. At this time, the inside of the firing furnace is maintained in a non-oxidizing atmosphere such as argon, helium, or nitrogen or an inert atmosphere. At this time, the inside of the firing furnace may be in a vacuum state.

Further, at the time of firing, it is preferable to suppress the volatilization of silicon carbide from the compact in order to promote the growth of the neck portion. As a method for suppressing the volatilization of silicon carbide from the molded body, there is a method of charging the molded body into a heat-resistant container capable of blocking invasion of the outside air. As a material for forming the heat-resistant container, graphite or silicon carbide is preferable.

In the subsequent metal impregnation step, the porous body is impregnated with metal as follows. For example, when impregnating metal silicon, it is preferable to impregnate the sintered body with a carbonaceous substance in advance. Such carbonaceous materials include:
For example, various organic substances such as furfural resin, phenolic resin, lignin sulfonate, polyvinyl alcohol, corn starch, beet sugar, coal tar pitch, alginate and the like can be mentioned. It should be noted that pyrolytic substances such as carbon black and acetylene black can also be used.

By impregnating the carbonaceous material in advance, a new silicon carbide film is formed on the surface of the open pores of the sintered body, whereby the bond between the molten silicon and the porous body is strengthened. It becomes something. Further, the impregnation of the carbonaceous material increases the strength of the sintered body.

As a method of filling the open pores with the metallic silicon, for example, a method of impregnating the metallic silicon by heating and melting can be mentioned. Alternatively, a method in which finely divided metal silicon is dispersed in a dispersion medium, the dispersion is impregnated in a porous body, dried, and heated to a temperature equal to or higher than the melting temperature of metal silicon can also be applied. The impregnation of the metal may be performed on the compact before firing. Thereafter, if necessary, the sintered body is cut and polished to obtain a plate-shaped body having a predetermined shape, thereby producing a radiator plate.

The heat radiating plate made of the silicon carbide / metal composite having a new structure thus obtained has a thermal conductivity of 1
It has excellent thermal conductivity of 00 W / m · K or more and also has excellent mechanical strength because it contains metal. further,
Depending on the manufacturing conditions, the thermal conductivity is 180 to 280 W / m ·
K, 200 to 260 W / m · K. Such a radiator plate is most suitable as a radiator plate used for a module substrate described below.

Next, a description will be given of a module substrate using the above-mentioned heat sink. A module substrate according to the present invention includes: a semiconductor element including: an insulating substrate having a conductive circuit formed on one main surface; and a heat sink joined to another main surface of the insulating substrate via a metal layer. A module substrate for mounting the silicon carbide.
A heat radiating plate made of a metal composite is used.

FIG. 1 is a cross-sectional view schematically showing a power module using the module substrate of the present invention.

In this power module 10, a conductor circuit 15 is formed on the upper surface of the insulating substrate 12, and a semiconductor element 16 is connected and fixed to a part of the conductor circuit via a solder layer 17. Other parts and semiconductor element 1
6 is connected by wire bonding using a wire 15a. An external terminal 19 is connected to one end of the conductor circuit 15 via a solder layer 18.

On the other hand, a metal layer 13 is formed on almost the entire bottom surface of the insulating substrate 12, and the heat radiating plate 11 made of the composite of the present invention is directly joined to the metal layer 13 made of aluminum or the like. Heat sink 11 is cooling unit 2
It is attached to 0. The radiator plate 11 may be joined to the metal layer 14 via a brazing material having a thermal expansion coefficient close to that of aluminum or the like and to which Al-Si is added.

The cooling unit 20 may be air-cooled or water-cooled. In case of water cooling type,
Normally, a coolant such as water flows in a portion in contact with the heat sink 11.

In this power module 10, the insulating substrate 12 having the conductor circuit 15 and the metal layer 13 and the heat sink 11 constitute the module substrate of the present invention. As the heat radiating plate 11, a heat radiating plate made of the above-described silicon carbide / metal composite is used. This heat radiating plate has an extremely high thermal conductivity of, for example, 200 to 260 W / m · K by selecting manufacturing conditions. As well as excellent mechanical properties. The heat sink 11 has a thermal expansion coefficient of 3.5 × 10 ^{−6 to} 5.0 × 10 ⁻⁶ (/ ° C.) from room temperature to 800 ° C., and aluminum nitride (thermal expansion coefficient: about 4.5 × 10 ⁶ ). ^-6 / ℃)
And so on, so that they exhibit excellent durability even with temperature cycles. The thickness of the heat radiating plate 11 is usually preferably 3 to 4 mm.

The material of the insulating substrate 12 is not particularly limited.
For example, alumina, silicon nitride, aluminum nitride and the like can be mentioned, and among these, aluminum nitride having excellent thermal conductivity is preferable. When the insulating substrate 12 is made of aluminum nitride, the aluminum nitride sintered body
It may contain 0.1 to 10% by weight of a metal oxide such as an alkali metal oxide, an alkaline earth metal oxide and a rare earth oxide. These oxides include, for example, Y ₂ O
₃ , CaO, Li ₂ O, Rb ₂ O _{3 and the} like.

The material of the conductor circuit 15 and the metal layer 13 includes, for example, copper and aluminum, but aluminum having relatively high conductivity and low deformation resistance is preferable. In particular, when aluminum is used for the metal layer 13, it can be directly joined to the heat sink 11. In particular, when aluminum or silicon is used as the metal to be impregnated in the heat radiating plate 11, the aluminum and silicon in the heat radiating plate are melted and mixed with each other at the bonding interface, so that the two are strongly bonded. The bonding between the insulating substrate and the conductor circuit is performed, for example, using Al-
It can be performed using a brazing material containing Si.

The semiconductor element mounted on the module substrate of the present invention is not particularly limited.
Because of its excellent heat dissipation characteristics, it is most suitable for mounting semiconductor elements that generate a large amount of heat during operation. Examples of such a semiconductor element include IGBT and SIT. As described above, the module substrate of the present invention has excellent heat dissipation characteristics and also has excellent durability against thermal shock such as a temperature cycle.

[0053]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 First, as starting materials, a coarse powder of α-type silicon carbide having an average particle diameter of 30 μm (# 400) and a fine powder of α-type silicon carbide having an average particle diameter of 0.3 μm (GMF-15H2) Was prepared.
Then, 30 parts by weight of the fine powder were blended with 100 parts by weight of the coarse powder, and were uniformly mixed.

Next, 5 parts by weight of polyvinyl alcohol, 3 parts by weight of phenol resin, and 50 parts by weight of water are blended with 100 parts by weight of this mixture, and then mixed in a ball mill for 5 hours to obtain a uniform mixture. Obtained.

After the mixture was dried for a predetermined time to remove a certain amount of water, an appropriate amount of the dried mixture was collected and granulated. At this time, the water content of the granules was reduced to about 0.8% by weight.
It was adjusted to become. The granules of this mixture are then
It was formed at a pressing pressure of 1.3 t / cm ² using a metal stamping die. The density of the obtained plate-shaped green compact was 2.6 g.
/ Cm ³ .

Next, the compact was placed in a graphite crucible and fired using a tanman type firing furnace. The firing was performed in an argon atmosphere at 1 atm. In addition, at the time of baking, heating was performed to a maximum temperature of 2200 ° C. at a rate of 10 ° C./min, and thereafter, the temperature was maintained for 4 hours.

Next, the obtained porous sintered body was previously impregnated with a phenol resin (carbonization ratio: 30% by weight) under vacuum,
Drying was performed. Thereafter, the surface of the porous sintered body was coated with a slurry containing metallic silicon. Here, 100 parts by weight of metal silicon powder having an average particle diameter of 20 μm and a purity of 99% by weight or more,
% Acrylic acid ester / benzene solution (60 parts by weight) was used. Then, the porous sintered body coated with metallic silicon is placed in an argon gas stream for 450 minutes.
The mixture was heated at a rate of temperature rise of 1 ° C./hour and maintained at a maximum temperature of 1450 ° C. for about 1 hour. By such a treatment, metallic silicon was permeated into the porous sintered body to obtain a silicon carbide / metal composite. Here, the content of metallic silicon with respect to 100 parts by weight of silicon carbide was set to 30 parts by weight.

The substrate comprising the obtained silicon carbide / metal composite has an open porosity of 20% in the porous structure,
The overall thermal conductivity was 210 W / m · K, and the overall density was 3.0 g / cm ³ . The average particle size of the silicon carbide crystal was 30 μm. Specifically, it contained 20% by volume of fine crystals having an average particle size of 1.0 μm and 80% by volume of coarse crystals having an average particle size of 40 μm.

Subsequently, the base material is subjected to a facing process by a conventionally known method, and then a polishing process or the like is performed to obtain a vertical length of 70 m.
m, width: 130 mm, thickness: 3 mm Preparation of the heat sink was completed.

Next, as an insulating substrate having a conductor circuit or the like, a conductor circuit made of aluminum having a thickness of 0.4 mm on one side is joined using a brazing material containing Al--Si, and the other side is made of aluminum. Using a 4 mm-thick aluminum nitride substrate to which the plate was joined using the same brazing material, the obtained heat sink and the above-mentioned aluminum nitride substrate were joined by heating and pressure bonding with the aluminum plate interposed therebetween. Thus, the fabrication of the module substrate was completed.

The obtained module substrate was subjected to a heat cycle test in which a heat cycle of maintaining the temperature at -55 ° C. and then maintaining the temperature at 150 ° C. 1,000 times was repeated 1,000 times. Microscope observation of the bonding state with the insulating substrate and the bonding state between the conductor circuit and the metal layer and the insulating substrate revealed no cracks or the like.

Next, an IGBT was added to this module substrate.
After mounting the element and attaching it to the cooling unit, the power module was actually operated and the temperature of the IGBT element was measured. The IGBT element maintained a temperature at which it could function sufficiently as an element.

Example 2 Crude powder of α-type silicon carbide having an average particle diameter of 35 μm (# 360)
And with respect to 100 parts by weight of the coarse powder,
40 parts by weight of the above fine powder were blended and uniformly mixed. Other conditions were basically the same as in Example 1.

As a result, the obtained substrate made of the silicon carbide / metal composite had a porosity of 17% of open pores in the porous structure, an overall thermal conductivity of 220 W / m · K,
The overall density was 3.0 g / cm ³ . Also,
The average particle size of the silicon carbide crystals was 36 μm. Specifically, it contained 20% by volume of fine crystals having an average particle size of 1.0 μm and 80% by volume of coarse crystals having an average particle size of 45 μm.

Using this silicon carbide / metal composite, a module substrate was prepared in the same manner as in Example 1, and a heat cycle test was performed. Then, the bonding state between the heat sink and the insulating substrate and the bonding of the conductor circuit were performed. The state was observed, but no cracks or the like were observed at all.

Further, an IGBT is provided on the module substrate.
The temperature of the IGBT element was measured by mounting the element and attaching it to the cooling unit and operating it.
The element maintained a temperature at which the element could function sufficiently.

Example 3 Coarse powder of α-type silicon carbide having an average particle size of 57 μm (# 240)
And with respect to 100 parts by weight of the coarse powder,
40 parts by weight of the above fine powder were blended and uniformly mixed. Other conditions were basically the same as in Example 1.

As a result, the obtained substrate composed of the silicon carbide / metal composite had a porosity of open pores in the porous structure of 15%, an overall thermal conductivity of 230 W / m · K,
The overall density was 3.1 g / cm ³ . Also,
The average particle size of the silicon carbide crystals was 65 μm. Specifically, it contained 20% by volume of fine crystals having an average particle size of 1.0 μm and 80% by volume of coarse crystals having an average particle size of 80 μm.

Using this silicon carbide / metal composite, a module substrate was prepared in the same manner as in Example 1, and a heat cycle test was performed. Then, the bonding state between the heat sink and the insulating substrate and the bonding of the conductor circuit were performed. The state was observed, but no cracks or the like were observed at all.

Further, an IGBT is provided on the module substrate.
The temperature of the IGBT element was measured by mounting the element and attaching it to the cooling unit and operating it.
The element maintained a temperature at which the element could function sufficiently.

COMPARATIVE EXAMPLE 1 A coarse powder of α-type silicon carbide having an average particle size of 10 μm was used, and 45 parts by weight of fine powder of α-type silicon carbide having an average particle size of 0.7 μm were used with respect to 100 parts by weight of the coarse powder. Was blended and mixed uniformly.

After blending 5 parts by weight of polyvinyl alcohol and 50 parts by weight of water with respect to 100 parts by weight of this mixture, they were mixed in a ball mill for 5 hours to obtain a uniform mixture.

After the mixture was dried for a predetermined time to remove water to some extent, an appropriate amount of the dried mixture was collected and granulated. Next, the granules of this mixture were molded using a metal mold at a pressing pressure of 0.6 t / cm ² . The density of the obtained plate-shaped green compact was 2.0 g / cm ³ . Thereafter, the compact was impregnated with metallic silicon under the same conditions as in Example 1.

Next, the compact was placed in a graphite crucible and fired using a tanman firing furnace. The firing was performed in an argon atmosphere at 1 atm. In addition, at the time of sintering, heating was performed at a heating rate of 10 ° C./min to a maximum temperature of 1700 ° C., and thereafter, the temperature was maintained for 4 hours.

The base material comprising the obtained silicon carbide / metal composite has a porosity of 38% for open pores in a porous structure,
The overall thermal conductivity was 80 W / m · K, and the overall density was 2.8 g / cm ³ . The average particle size of the silicon carbide crystal was 10 μm.

Using this silicon carbide / metal composite, a module substrate was produced in the same manner as in Example 1. In addition, an IGBT element was mounted on the module substrate, and the IGBT element was mounted on a cooling unit and operated, and the temperature of the IGBT element was measured. It has exceeded the temperature at which it can function.

[0078]

As described above, the heat sink made of the silicon carbide / metal composite of the present invention has a sufficiently high thermal conductivity and a substantially high coefficient of thermal expansion with the aluminum nitride substrate. Since they are equal, they have excellent durability against temperature cycles and can be suitably used as a module substrate for mounting a semiconductor element that generates a large amount of heat. Further, since the module substrate of the present invention is configured as described above, it is excellent in heat radiation characteristics and durability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a module substrate of the present invention.

FIG. 2 is an SEM photograph showing a structure of a silicon carbide / metal composite constituting a heat sink of the present invention.

FIG. 3 is an SE showing the structure of a conventional silicon carbide / metal composite.
It is an M photograph.

FIG. 4 is an SEM photograph showing the structure of the silicon carbide / metal composite constituting the heat sink of the present invention.

FIG. 5 is an SE showing the structure of a conventional silicon carbide / metal composite.
It is an M photograph.

FIG. 6 is a sectional view schematically showing a conventional power module.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Power module 11 Heat sink 12 Insulating substrate 13 Metal plate 14, 17, 18 Solder layer 15 Conductor circuit 15a Wire 16 Semiconductor element 17, 18 Solder layer 19 External terminal

Claims (3)

[Claims] 1. A heat radiating plate comprising a silicon carbide / metal composite in which open pores are present in a porous structure composed of silicon carbide crystals and a metal is impregnated in the open pores, The average grain size of the crystal is 20 μm or more, the porosity is 30% or less, the thermal conductivity is 100 W / m · K or more, and 15 to 50 parts by weight of metal is impregnated with respect to 100 parts by weight of silicon carbide. A heat sink comprising a silicon carbide-metal composite, characterized by the following. 2. The composition contains 10 to 50% by volume of fine silicon carbide crystals having an average particle size of 0.1 to 1.0 μm and 50 to 90% by volume of coarse silicon carbide crystals having an average particle size of 25 to 150 μm. A heat sink comprising the silicon carbide / metal composite according to claim 1. 3. A semiconductor element comprising: an insulating substrate having a conductive circuit formed on one main surface; and a heat radiating plate joined to another main surface of the insulating substrate via a metal layer. 2. The module substrate according to claim 1, wherein the radiator plate includes:
A substrate for a module, wherein the radiator plate according to any one of the preceding claims is used.