JP2003073756A - Composite material and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a composite material having excellent low thermal expansibility. SOLUTION: The method for manufacturing the composite material is characterized by having a filling step of filling a SiC powder in dies as a dispersion material, a preheating step of preheating the dies to a reaction initiation temperature or higher, at which a molten metal of a matrix metal containing Al as a main component and SiC particles start the reaction, and a teeming process of teeming the molten metal of the matrix metal having a temperature equal to or higher than the reaction initiation temperature, into the dies after the filling process and the preheating process, pressurizing it, and impregnating the molten metal among the SiC powders. The molten metal temperature and the preheating temperature, both of which are made to be equal to or higher than the reaction initiation temperature, make the substance with low thermal expansibility crystallize or generate, to provide the composite material with low thermal expansibility, without greatly reducing thermal conductivity. The composite material is particularly suitable for a heat sink member for electronic instruments.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a composite material in which SiC particles are dispersed in a matrix metal containing Al as a main component. In particular, the present invention relates to a method of manufacturing a composite material suitable for a heat dissipation member for electronic devices that radiates heat of electronic devices such as semiconductor chips to the outside.

[0002]

2. Description of the Related Art Highly integrated semiconductor chips and modules in which they are densely arranged on a substrate are used for controlling various devices. A device such as a semiconductor chip or the like usually has a specified operating temperature range, and malfunctions occur when the temperature exceeds the range, so heat generated from the semiconductor chip or the like needs to be appropriately radiated. Therefore, conventionally, a heat dissipation member such as a heat sink has been provided on the lower surface of the semiconductor chip or the substrate. Therefore, such a heat dissipation member needs to have high thermal conductivity.

Further, the heat dissipating member is required to have low thermal expansion in addition to its high thermal conductivity. This is for suppressing thermal distortion of the heat dissipation member itself, separation of the heat dissipation member from the semiconductor chip or the substrate (for example, separation of solder), and the like.

When a single metal such as aluminum (Al) is used as the heat dissipation member, it is difficult to achieve both high thermal conductivity and low thermal expansion. When a Si-based ceramic material such as SiC is used, both characteristics can be balanced in a high dimension, but the ceramic alone has poor toughness and is weak against impact. In particular, the heat radiation member may be cracked or damaged by an impact applied to the heat radiation member during processing, assembly, use, or the like.

Therefore, a metal-ceramic composite material is used for a heat dissipation member in order to satisfy a good balance of high thermal conductivity, low thermal expansion property, high reliability and the like. For example, JP-A-11-228261 and JP-A-11-116363.
Japanese Patent Laid-Open No. 11-140560 or Japanese Patent Laid-Open No. 11-140560 discloses such a composite material. Each of these composite materials is manufactured by impregnating a preformed body (preform) obtained by molding and firing a ceramic powder mixed with a binder with a molten metal of a matrix metal under high pressure.

[0006]

By the way, in the case of the conventional composite material, the melt temperature of the matrix metal to be impregnated into the preform is merely selected in consideration of its impregnating property and the handleability of the melt. It was The thermal conductivity and coefficient of linear expansion of the obtained composite material are affected by the degree of impregnation of the molten metal, etc., and are the ratios of the metal and ceramics used, that is, those that substantially comply with the composite rules. It was

However, as a result of repeating various experiments, the inventor of the present invention has found that the linear expansion coefficient of the composite material has an influence on the melt temperature of the metal matrix and the preheating temperature of the mold filled with the ceramic particles, in addition to the simple composite rule. I found that it will be done.

The present invention has been made in view of such circumstances. That is, by utilizing this knowledge, a metal that can achieve both higher thermal conductivity and higher thermal expansibility than ever before.
An object of the present invention is to provide a method for producing a composite material made of a ceramic composite material.

[0009]

The present inventor has conducted further research based on the above findings. As a result, when the matrix metal (Al) and the ceramic particles (SiC) come into contact with each other at a predetermined temperature or higher, a low thermal expansion material (hereinafter,
It is called a "low thermal expansion material". ) Was crystallized or generated, high thermal conductivity was maintained, and the thermal expansion property of the entire composite material was confirmed to be reduced, and the present invention was completed. (Method for producing composite material) That is, the method for producing a composite material of the present invention is the method for producing a composite material in which SiC particles are dispersed in a matrix metal containing Al as a main component.
The filling step of filling the mold with iC powder and the preheating temperature of the mold are controlled by the melt of the matrix metal and the S in the SiC powder.
A preheating step at which the temperature of the iC particles starts the reaction or higher, and a mold after the filling step and the preheating step are poured with the molten metal of the matrix metal having the molten temperature of the reaction starting temperature or higher. A pouring step of pressing the SiC powder to impregnate the molten metal with the molten metal.

In the manufacturing method of the present invention, the preheating temperature in the preheating step and the molten metal temperature in the pouring step are set to be equal to or higher than the reaction start temperature at which the molten metal of the matrix metal and the SiC particles in the SiC powder start the reaction. As a result, we succeeded in lowering the expansion coefficient of the composite material without significantly lowering its thermal conductivity. Although the details of this mechanism are not always clear, it is considered that low thermal expansion substances (Si and Al ₄ C ₃ ) are newly crystallized and generated at the interface between the SiC particles and the matrix metal. Therefore,
The "reaction" in the present invention means a state that enables the low thermal expansion material to effectively appear in the pouring step or the subsequent cooling and solidifying steps. In other words, not only chemical reactions,
Elution into the metal matrix of SiC is included in the reaction here.

The reaction initiation temperature is generally 800 ° C. or higher, although it depends on the composition of the metal matrix. Therefore, for example, the preheating temperature or the molten metal temperature is set to 8
00 ° C, 850 ° C, 875 ° C, 900 ° C, 925 ° C, 9
It can be selected from 50 ° C and the like. More specifically,
When the matrix metal is pure Al or Al alloy containing 90 mass% or more of Al, it is more preferable to set the preheating temperature and the molten metal temperature to 850 to 1000 ° C. The upper limit of the preheating temperature is 1000 ° C,
If it exceeds 1000 ° C., the strength of the mold is lowered and the amount of deformation thereof is increased, which is not preferable. Also,
There is no special upper limit on the melt temperature, but it is 1000.
It is not economical to maintain above ℃.

The preheating step according to the present invention may be one in which the mold and SiC powder are heated to a predetermined temperature or higher before the start of the pouring step. Therefore, the preheating step may be started not only after the completion of the filling step but also during the filling step or before the start of the filling step.

By the way, in the present invention, the mold and the SiC
Since the preheating temperature of the powder and the temperature of the molten metal are sufficiently high, even if the molten metal of the matrix metal comes into contact with the mold or the SiC powder during the pouring process, the molten metal does not easily solidify and the S
It becomes possible to sufficiently impregnate the iC powder. In other words, the generation of unimpregnated parts that causes a decrease in the thermal conductivity of the composite material is suppressed,
To be prevented.

Further, in the manufacturing method of the present invention, in the filling step, the cavity of the mold is directly filled with SiC powder,
There is no need for molding and firing steps of preforms. Therefore, a high-performance composite material can be efficiently obtained at low cost. Further, since the production of the preform can be omitted, it is possible to prevent a binder or the like having low thermal conductivity or high thermal expansion from being mixed into the composite material.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to embodiments. (1) In the filling step and the SiC powder filling step, the SiC powder filled in the mold may be one kind of powder or a mixture of plural kinds of powder.
SiC has a much smaller linear expansion coefficient and a larger thermal conductivity than matrix metals such as Al. Therefore, SiC
The more the powder is filled into the matrix metal (the larger the filling rate is), the more the low thermal expansion property and the high thermal conductivity of the composite material can be compatible with each other.

However, the thermal conductivity (thermal conductivity) is affected not only by the filling rate but also by the area of the interface formed between the matrix metal and the SiC particles. Therefore, it is preferable to increase the filling rate and reduce the area of the interface in order to obtain high thermal conductivity of the composite material. If the SiC particles having a large average particle size are simply dispersed, the area of the interface is reduced, but the filling rate is also decreased and the desired linear expansion coefficient cannot be obtained. On the other hand, when SiC particles having a small average particle size are dispersed, even if the packing rate can be increased, the area of the interface increases and the thermal conductivity decreases. Further, SiC particles having an average particle size that is too small tend to agglomerate and rather reduce the filling rate.

Therefore, the present inventor has developed, in addition to the above-described manufacturing method, a SiC powder capable of further balancing low thermal expansion and high thermal conductivity in a high dimension. That is, the SiC powder is composed of SiC coarse particles having a large average particle diameter and SiC fine particles having a small average particle diameter.
The volume ratio of coarse particles to SiC fine particles is 1.5 to 4, S
The average particle size ratio of the iC coarse particles to the SiC fine particles is 10 to
It was found that a value of 15 is more preferable. And
It was also found that the filling rate (the ratio of the SiC powder when the entire composite material is 100% by volume) at this time is preferably 65 to 75% by volume. More preferably, the average particle size ratio is 11
-14, the volume ratio is 2-3, and the filling rate is 68-72% by volume, which is more preferable.

If the average particle size of the SiC particles is specifically described, if the average particle size of the SiC coarse particles is 50 to 300 μm and the average particle size of the SiC fine particles is 5 to 30 μm,
It is suitable. The average particle size of the SiC coarse particles is 50 to 200 μ.
m, 75 to 150 μm, and more preferably 75 to 125 μm. In addition, the average particle size of the SiC particles is 5
More preferably, it is set to -20 μm, 5 to 15 μm, and further 7 to 10 μm.

Here, the average particle size is an average of particle sizes measured by a sieving test method and an electric resistance method (JIS R6002).

It should be noted that such a SiC powder may be any one in which coarse SiC particles and fine SiC particles are mixed, and the method for producing the same is not limited. SiC may be mechanically or chemically pulverized to be produced, or commercially available SiC powders having different average particle sizes may be mixed. Further, within a range not departing from the gist of the present invention, the composite material or SiC powder is
Third particles (SiC particles having different particle diameters, other ceramic particles, etc.) other than the SiC fine particles and the SiC coarse particles may be included. (2) Pouring Process The molten metal temperature of the metal matrix is as described above.
In the case of the present invention, since the temperature of the molten metal is sufficiently high, the impregnability of the molten metal between the SiC powders is good. However, unless the molten metal is pressed, the molten metal is not sufficiently impregnated between the SiC powders.
Therefore, a pressure of about 50 to 150 MPa is applied to the molten metal. For example, when the pure Al melt is used, the pressure is preferably 70 to 120 MPa.

The matrix metal preferably has low thermal expansion and high thermal conductivity even after the reaction with SiC or after solidification. As long as it is such, alloy elements and the like are not particularly concerned, but in consideration of the reaction with SiC, for example, pure A
1 (purity of 98% or more) is preferable.

After the pouring process, cooling, solidifying process,
It goes without saying that the mold release step, the processing step and the like are appropriately performed. (3) Heat Dissipating Member for Electronic Equipment The composite material obtained by the manufacturing method of the present invention is preferably used for a heat radiating member for electronic equipment. This heat dissipation member for electronic devices transfers heat generated from the heat dissipation members to the outside in order to dissipate the heat from the electronic devices. However, it is not limited to so-called heat sinks. For example, it may be a member for thermal expansion matching that intervenes between a heat sink made of a metal such as an Al alloy and a ceramic substrate to transfer heat, a housing case for electronic equipment, and the like.

[0023]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. (Manufacturing Method of Composite Material) A plate-like Al—SiC composite material of 3 × 50 × 80 mm was manufactured by using the above-described manufacturing method according to the present invention.

Two types of Si having different average particle diameters of SiC particles
A SiC mixed powder prepared by mixing C powder (manufactured by Showa Denko KK) was prepared (“SiC powder” in the present invention). That is, SiC powder composed of coarse SiC particles having an average particle size of 100 μm and SiC powder composed of SiC fine particles having an average particle size of 8 μm were mixed at a volume ratio of 7: 3 (mixing step), A SiC mixed powder was prepared. In addition, this Si
The C mixed powder has an average particle size ratio of 12.5 and a volume ratio of 2.3.
Equivalent to.

Next, this SiC mixed powder was filled into a mold having a concave cavity along the shape of the composite material (filling step). At the time of this filling, no particular pressure was applied and neither binder nor the like was mixed. However, if the filling process is performed while applying vibration to the mold, each SiC in the cavity is
The movement of the particles is promoted, and the particles are arranged so as to fill the gaps with each other, so that the bulk density and the filling rate of the composite material can be further improved.

Next, pure Al (J
A molten metal in which IS A1050: melting point 660 ° C.) was dissolved was prepared. This molten metal is heated in the range of 700 to 950 ° C. to 50
It was changed at each temperature of ℃, and the melt held at each temperature was poured from the pouring port of the mold and pressurized (pouring process). The pressure applied at this time was 100 to 140 MPa, which was common to all the melts.

Before this pouring step, the mold is pre-set to 90
It was heated to 0 ° C. (preheating step). The same pouring process was performed also when the mold (preheating) temperature was 700 ° C. In this example, the mold was heated by an electric heater, and the temperature of the mold was set as the preheating temperature.

After these pouring steps, the mold was air-cooled to solidify the molten metal (solidification step), and then the cast product was taken out from the mold (mold release step) to obtain an Al-SiC composite material.

Although not carried out in the present embodiment, the composite material obtained is cut if necessary to secure the surface roughness and flatness of the surface in contact with the electronic device, and the heat dissipation member for the electronic device. Can also be (Measurement of Composite Material) The thermal conductivity and the coefficient of linear expansion of the composite material obtained from various molten metal temperatures were measured. Figure 1
And the melt temperature (° C) on the horizontal axis, thermal conductivity (W / mK)
And the linear expansion coefficient (× 10 −6 / ° C.) as the vertical axis,
The graph which plotted those relationships is shown.

The thermal conductivity was determined according to JIS R1611 using a laser flash method thermal constant measuring device (manufactured by Vacuum Riko Co., Ltd., TC-7000). The linear expansion coefficient was determined by mechanical analysis TMA120C (Seiko Instruments).

Further, when the filling rate of the SiC mixed powder of each composite material was determined by the Archimedes method, it was about 70% with respect to the whole. (Evaluation) From FIG. 1, the preheating temperature was set to 900 ° C., the molten metal temperature was set to 850 ° C. (reaction start temperature in this example) or more,
It can be seen that the linear expansion coefficient of the composite material obtained when the temperature is 900 ° C. or higher is extremely low. Moreover, at this time,
The thermal conductivity was about 210 W / mK or more, and it was confirmed that high thermal conductivity was secured.

On the other hand, when the preheating temperature was 700 ° C., the coefficient of linear expansion hardly changed even when the temperature of the molten metal increased, and maintained a high value. It is considered that this is because there was no crystallization or formation of the low thermal expansion material that reduces the linear expansion coefficient. (Composition of composite material) Next, the preheating temperature and the melt temperature are set to 9
Structure photographs of the composite materials of the above-mentioned examples manufactured at 00 ° C. are shown in FIGS. 2 (a) and 2 (b). Figure 2 (a)
[Fig. 3] is a microstructure photograph observed at a magnification of 50 with a metallurgical microscope. White dendritic (dendritic) substances are Si crystallized substances (crystallized Si). FIG. 2 (b) is a micrograph of a structure at a magnification of 1000 times observed with a metallurgical microscope. It can be seen that Si alone crystallizes at the interface of SiC particles having large and small particle sizes.

[0033]

According to the manufacturing method of the present invention, a composite material exhibiting a lower thermal expansion property is obtained by crystallizing or generating a low thermal expansion material while maintaining a high thermal conductivity.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a molten metal temperature, a thermal conductivity and a linear expansion coefficient according to this example.

FIG. 2 is a microstructure photograph of the composite material of this example. The figure (a) is a metallurgical microscope photograph of 50 times, and the figure (b) is a metallurgical microscope of 1000 times.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Chihei Sugiyama             2-1, Toyota-cho, Kariya City, Aichi Stock Association             Inside Toyota Toyota Industries (72) Inventor Takashi Yoshida             2-1, Toyota-cho, Kariya City, Aichi Stock Association             Inside Toyota Toyota Industries (72) Inventor Eiji Kono             2-1, Toyota-cho, Kariya City, Aichi Stock Association             Inside Toyota Toyota Industries F term (reference) 4K020 AA22 AC01 BB26

Claims (3)

[Claims] 1. A method of manufacturing a composite material in which SiC particles are dispersed in a matrix metal containing Al as a main component, wherein a step of filling a mold with SiC powder and a preheating temperature of the mold are the same as those of the matrix metal. Of the molten metal and the SiC particles in the SiC powder start the reaction at a temperature higher than the reaction start temperature, and the mold after the filling step and the preheating step has a temperature of the melt higher than the reaction start temperature. A pouring step of pouring a molten metal and pressurizing it to impregnate the SiC powder with the molten metal. 2. The matrix metal is 90 mass% of Al.
It is pure Al or Al alloy contained above, and the preheating temperature and the molten metal temperature are 850 to 1000.
The method for producing a composite material according to claim 1, wherein the temperature is ° C. 3. The method for producing a composite material according to claim 1, wherein the composite material is used for a heat dissipation member for electronic equipment.