JPH104160A - Heat radiating material for semiconductor substrate and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide heat radiating material for a semiconductor substrate and its manufacturing method which can reduce a manufacturing cost and can attempt a high performance of a material quality. SOLUTION: A two element mixture of metal particles and ceramic particles is sealed into sheath material by vacuum seal without adding such a third element as Ag and so on, by cold working the mixture and by heat working after a sudden heating. Compounds caused by isolating Si can be suppressed, sinter density is improved and thermal conductivity is improved. Additionally, the metal particles can largely be deformed by a high pressure during heating condition, and can tightly be contacted with a phase boundary with the ceramic particles, and the sinter density and the thermal conductivity are further improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a heat radiating material used for an LSI package, an optical semiconductor package or the like.

[0002]

2. Description of the Related Art Conventionally, Cu-W based heat radiating materials have been generally used. However, tungsten (W) is expensive, has a large specific gravity, and has a problem that the whole product becomes heavy. . In addition, as a method of manufacturing, the W powder is sintered by a hot press method, then impregnated with Cu, and ground to a predetermined shape. This increases the number of steps and lowers the material yield, thereby increasing productivity. And the production cost rises.

[0003] Therefore, Cu-SiC-based composite materials and Cu-C-based composite materials have attracted attention in place of W, which has a high raw material cost and a large specific gravity.
The hot press method is mainly used to form the heat radiating material as in the case of the W-based material, and since this method is a batch process, there remains a problem that productivity is poor (production cost is high). In addition, in a certain system, there is a problem that the characteristics of the sintered body are deteriorated when the heating time by the hot press is prolonged.

FIGS. 4 (a) to 4 (c) show characteristics of a Cu--SiC hot press sintered body. In this material system, the thermal conductivity is reduced by heating at a high temperature for a long time. this is,
This is because free Si in SiC reacts with Cu to produce a compound that becomes a resistance at the interface. In the case of the hot pressing method, it is necessary to add a eutectic melting point element such as Ag, Sn, or Si in order to improve the sintering density and the thermal conductivity of the two elements of Cu-SiC. , Especially A
In a system containing g, Ag is precipitated and expanded by heating at a high temperature for a long period of time, which also reduces the thermal conductivity. Here, as shown in FIG. 4C, as the pressure increases, the characteristics become better, but it is usually difficult to increase the pressure too much due to the limitation of the strength of the sintering jig using carbon.

[0005] It is also conceivable to combine cold pressing and continuous sintering.
In the case of a system, high density cannot be obtained because the ductility of SiC is extremely low. For example, even when a Cu—SiC—Ag system is applied with a high pressure of 784 MPa by cold pressing, only a low density of 74% relative density before heat treatment and 73% after heat treatment can be obtained.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and its main purpose is to reduce the manufacturing cost and improve the performance of the material. It is an object of the present invention to provide a heat radiating material for a semiconductor substrate and a manufacturing method thereof.

[0007]

For this purpose, a Cu-SiC two-element material to which no third element such as Ag is added is used, the heating rate is increased, the heating holding time is shortened, and the compound of free Si is used. Must be suppressed. Also,
It is necessary to significantly deform Cu by applying a pressure of at least 100 MPa or more in a heated state and to make the Cu adhere to the interface with the SiC particles.

[0008] The above object is achieved according to the present invention by providing a Cu—S
A heat dissipating material for a two-element semiconductor substrate of iC, comprising metal (Cu) particles and ceramic (SiC) encapsulated in a sheath material
The mixture with the particles is cold-worked, hot-worked after rapid heating, the sintering density is at least 94%, the thermal conductivity is at least 120 W / mK, and the metal particles are stretched (aspect ratio). (2: 3 or more), a heat dissipating material for a semiconductor substrate, and a mixture of metal particles and ceramic particles encapsulated in a sheath material, which is cold-worked and rapidly heated. This is achieved by providing a method of manufacturing a heat radiating material for a semiconductor substrate, which has a step of performing hot working later.

[0009]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a main part of a manufacturing process of a heat radiating material for a semiconductor substrate to which the present invention is applied.

First, the vicinity of one end (the right side in the drawing) of a tube (sheath material) made of SUS having a circular cross section is pressed from the side, and the end is closed by TIG welding. Then, from the other side (left side in the figure), copper powder (Cu) and silicon carbide powder (SiC)
After tapping the mixed powder of the above, pressing from the side in the same manner as described above while evacuating, cutting, and then closing the end face by TIG welding, mixing the above copper powder (Cu) and silicon carbide powder (SiC). The powder is vacuum-sealed. Hereinafter, the rolling reduction in the powder sheath rolling method is defined as follows. Reduction rate = ((thickness before rolling-thickness after rolling) / thickness before rolling)
× 100% In particular, when the sheath material is cold-rolled, the thickness before rolling is the outer diameter of the sheath material.

Next, after cold rolling is performed to increase the internal density, hot rolling is performed at a temperature of, for example, 800 ° C. to 850 ° C. to further increase the density to a flat plate shape, at least a sintered density of 94% or more. Then, the sheath material is removed and processed into a desired shape to be used as a heat radiating material for a semiconductor substrate. After the cold rolling and the hot rolling to a sintering density of 94% or more after the cold rolling, the thermal conductivity is 120 W / mK.
The above heat radiating material is obtained.

In this example, the procedure for producing a sheet material by rolling is shown. However, when producing rods and wires in accordance with applications and shapes, after extruding, rotary swaging or hole rolling, cold working and then hot working are performed. It may be processed during processing. As a method similar to the above-mentioned sheath rolling method, an HIP method is conceivable. However, since the heating speed is slow and the heating time is long, the characteristics of the heat dissipating material are deteriorated similarly to the hot press method.

[0014]

FIG. 2 compares the characteristics of the heat radiator obtained by the hot pressing method with the characteristics of the heat radiator obtained by the powder sheath rolling method according to the present invention.

In a Cu-SiC system having a volume ratio of SiC / Cu = 65/35, the relative density is 83 by hot pressing.
% And a thermal conductivity of 22 W / mK, but the powder sheath rolling method according to the present invention has a relative density of 98% and a thermal conductivity of 75%.
W / mK. In addition, the volume ratio of SiC / Cu =
In a 50/50 Cu-SiC system, the relative density is 95% and the thermal conductivity is 60 W / mK by the hot press method. However, in the powder sheath rolling method according to the present invention, the relative density is 98%, Thermal conductivity improved to 157 W / mK. Here, the density of the rolled powdered sheathed material is the rolling temperature, rolling reduction,
The density is affected by the roll diameter, the rolling speed, the strength of the sheath material, and the like. In general, the larger these values are, the higher the density is. FIG. 2 shows the results of using a sheath material having an outer diameter of 12 mm and a plate thickness of 1 mm, a roll diameter of 125 mm, a rolling speed of 22 m / min, a cold rolling rate = hot rolling rate = 50%, and a total rolling reduction rate of 75%. . Here, the influence of the strength of the sheath material appears greatly, and KOVAR (trademark: Fe-Ni-Co alloy developed by Westinghouse) having a large hot strength is used.
Excellent characteristics were shown when using. When the average rolling pressure is determined from the rolling load, the average KOVAR is about 200 MPa. In addition, about 100% of Cu having a low density of 94% is used.
a. However, this value is 2.5 times or more higher than that of the hot press method, and it is considered that the Cu particles are extended and the adhesion to the SiC particles is improved.

FIG. 3 shows a comparison of the structures of the heat dissipating material (FIG. 3 (a)) produced by the powder sheath rolling method of the present invention and the heat dissipating material (FIG. 3 (b)) produced by the conventional hot pressing method. In both cases, a Cu-SiC system having a volume ratio of SiC / Cu = 50/50 is used. In the powder sheath rolling method of the present invention, a SUS pipe is used as a sheath material, and after cold rolling at a rolling reduction of 50%, 1% at 850 ° C.
Immediately after heating for 0 minutes, hot rolling was performed at a rolling reduction of 44% (total rolling reduction of 72%, the outer diameter of the sheath material was reduced from 12 mm to a thickness of 3.36 mm after rolling). On the other hand, in the hot press method, 8
It was pressurized (39.2 MPa) at 60 ° C. for 2 hours.

Compared with the heat dissipating material obtained by the conventional hot pressing method shown in FIG. 3B, the heat dissipating material obtained by the powder sheath rolling method of the present invention shown in FIG. (2: 3 or more in aspect ratio).

As shown in Table 1, even when the powder sheath rolling method is used, the hot rolling is performed in two steps because the first step involves partial solidification without sufficiently increasing the overall density, or Since the heating time was prolonged, desired characteristics could not be obtained, and those subjected to only a simple heat treatment (850 ° C., 10 minutes) after cold rolling expanded and clearly had a poor density. Therefore, it is understood that a method of achieving a certain density by cold rolling and then further increasing the density by hot rolling is most excellent.

[0019]

[Table 1] Preconditions 1) Use of SUS sheath material 2) Heating condition before hot rolling or during heat treatment is 850
℃, 10 minutes 3) Use mixed powder of SiC / Cu = 50/50 in volume ratio

[0020]

As is apparent from the above description, according to the heat radiating material for a semiconductor substrate and the method of manufacturing the same according to the present invention, the metal particles and the ceramic particles are contained in the sheath material without adding a third element such as Ag. By vacuum-encapsulating a two-element mixture of the above and cold-working, hot-working after rapid heating, the compound with Cu due to free Si can be suppressed, and the sintering density is improved, The conductivity is improved. In addition, the metal particles are greatly deformed by applying high pressure in the heating state, and adhere to the interface with the ceramic particles.

[Brief description of the drawings]

1 (a) to 1 (g) are views showing a main part of a manufacturing process of a heat radiating material for a semiconductor substrate to which the present invention is applied.

FIG. 2 is a graph comparing characteristics of a heat radiator obtained by a conventional hot press method with characteristics of a heat radiator obtained by a powder sheath rolling method according to the present invention.

FIG. 3 (a) is a scanning electron microscope metallographic photograph (reflection electron beam image) showing the structure of a heat dissipation material for a semiconductor substrate according to the present invention, and FIG. 3 (b) shows the structure of a conventional heat dissipation material for a semiconductor substrate. Scanning electron microscope metal structure photograph (reflection electron beam image).

FIGS. 4 (a), (b) and (c) show the relationship between the sintering temperature, sintering time and sintering pressure in the conventional hot press method and the characteristics (thermal conductivity) of the product. Graph.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Takashi Kayamoto 3-10 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Japan Nippon Hojo Co., Ltd.

Claims (5)

[Claims] 1. A heat-dissipating material for a two-element semiconductor substrate of Cu-SiC, wherein metal (Cu) particles and ceramic (SiC) particles encapsulated in a sheath material are hot-worked after cold working. The sintering density is at least 94% and the thermal conductivity is 1
A heat radiating material for a semiconductor substrate, wherein the heat radiating material is 20 W / mK or more. 2. A heat dissipation material for a semiconductor substrate comprising a two-element composite material composed of metal particles and ceramic particles, wherein the metal particles extend in an aspect ratio of 2: 3 or more. Heat dissipation material for substrates. 3. A method of manufacturing a heat radiating material for a semiconductor substrate, comprising a step of encapsulating a mixture of metal particles and ceramic particles in a sheath material and subjecting the mixture to cold working and then hot working. 4. The cold working and the hot working are performed by rolling,
The method according to claim 3, wherein the method comprises one or a combination of extruding and rotary swaging. 5. The pressure during the hot working is 100MPa.
5. The method according to claim 3, wherein the distance is not less than a.
3. The method for manufacturing a heat radiating material for a semiconductor substrate according to claim 1.