JPH06196884A - High-heat-conductivity composite - Google Patents

Abstract

PURPOSE:To provide a high-heat-conductivity composite capable of reducing the thermal resistance at the contact between a heat-generating body and a cooling device so as to improve cooling efficiency of the heat-generating body. CONSTITUTION:A high-heat-conductivity composite 16 comprises filler particles 12 dispersed in matrix resin 11, and the filler particles are fused through metal mesh 15. The filler particles 12 dispersed in the matrix are made of metallic or organic material having a higher melting point than the metal mesh 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high thermal conductivity composite body, and more particularly to a high thermal conductivity composite body having a large effect of reducing thermal resistance and capable of greatly improving the heat dissipation characteristics of a heating element.

[0002]

2. Description of the Related Art Conventionally, there is a cooling system that reduces heat resistance by mounting or applying a heat dissipation body such as a heat dissipation sheet or heat dissipation grease on the surface of the heat generation body to promote heat dissipation from the heat generation body. It is used in a wide range of fields such as semiconductor parts, electronic parts, heavy electrical equipment, office equipment and energy related parts.

For example, in the field of semiconductor devices, a module structure 1 as shown in FIG. 6 is used. That is, the module structure 1 includes an LSI or a power IC, which is a heating element, on the upper surface of the ceramic substrate 2 having electrical insulation.
The semiconductor element 3 such as a semiconductor element 3 is mounted on the semiconductor element 3 in order to efficiently dissipate heat generated in the semiconductor element 3.
A radiation fin 4 as a cooling component is joined to the upper surface of the. However, since minute irregularities are formed on the joint surface between the semiconductor element 3 and the heat dissipation fin 4, the contact between the semiconductor element 3 and the heat dissipation fin 4 does not result in complete contact, and the intervening air layer serves as a thermal contact resistance, resulting in heat dissipation characteristics. Will decrease. Therefore, measures have been taken to increase the contact pressure between the radiation fin 4 and the semiconductor element 3 or to reduce the heat transfer resistance by filling the joint surface between them with the organic resin adhesive 5 having good thermal conductivity. .

By interposing this resin adhesive 5, the voids (irregularities) formed in the joint surface are filled to reduce the thermal contact resistance, and the heat 6 generated in the semiconductor element 3 is smoothly moved toward the radiation fins 4. To improve the heat dissipation characteristics.

On the other hand, as shown in FIG. 7, a semiconductor package 8 in which a semiconductor element 3 is mounted on a ceramic multilayer substrate 7.
In the case of mounting the heat sink 6 on the board 9 and dissipating the heat 6 generated in the semiconductor element 3 from the board 9 side,
A sheet-shaped or grease-shaped (paste-shaped) radiator 10 is interposed between the ceramic multilayer substrate 7 and the board 9.

Here, as a specific example of the sheet-shaped heat radiator 10, for example, boron nitride, beryllium oxide, or silicon carbide is used in a flexible organic material such as polyethylene, polyester, polypropylene, polyimide, or silicon rubber. A filler having a high thermal conductivity such as the above or the organic material is coated with the filler is used. On the other hand, as a specific example of the grease-like radiator 10, for example, a paste-like silicone resin adhesive having a high thermal conductivity is widely used.

By interposing the heat radiator 10 as described above, the degree of adhesion between the ceramic multilayer substrate 7 and the board 9 is improved, the heat transfer resistance is reduced, and the heat dissipation characteristic to the board 9 side is also improved.

[0008]

However, in the conventional sheet-shaped radiator as described above, there is a drawback that the organic material having flexibility generally has a low thermal conductivity but a relatively large coefficient of thermal expansion. there were. Therefore, when the sheet-shaped radiator is applied to the heating element, the heat generated in the heating element is not smoothly released to the outside of the system, or when the thermal expansion difference between the radiator and the heating element is large. However, there is a problem in that the adhesion reliability between the two is reduced.

On the other hand, as a heat radiator for dealing with the above problems, fine inorganic particles such as aluminum nitride or metal particles having high thermal conductivity as compared with other ceramic materials are dispersed as fillers in an organic matrix. There has also been proposed a composite for heat dissipation, which is composited, has a high thermal conductivity as a whole, and is excellent in flexibility.

However, in the heat dissipation composite prepared by mixing only the inorganic particles such as fine aluminum nitride raw material powder or the metal particles into the organic matrix such as the resin as in the above heat dissipation composite, the inorganic particles do not interact with each other. Since it has a structure in which the organic matrix having low thermal conductivity is interposed between the inorganic particles in a discontinuously dispersed state, there is a drawback that the thermal conductivity of the entire heat dissipation composite is unlikely to increase, such as in semiconductor devices. There is a problem in that the exhaust heat from the heat-generating component is likely to be stagnant and the cooling efficiency is difficult to improve.

On the other hand, due to recent advances in semiconductor manufacturing technology, high integration, high speed, and high power consumption of semiconductor elements are rapidly progressing. Since the amount of heat generated from a semiconductor element tends to further increase with the increase in power and high integration of such a semiconductor element, development of a high thermal conductive composite body that further enhances the heat dissipation of the semiconductor element has been pursued. It is sought after.

The present invention has been devised in order to meet the above-mentioned problems and requirements, and it is possible to reduce the thermal contact resistance between the heating element and the cooling component and to further improve the heat dissipation characteristics of the heating element. The purpose is to provide a conductive composite.

[0013]

In order to achieve the above object, the present inventors have added various inorganic compositions and fillers such as metal particles to various matrix materials to form a heat-radiating composite. The heat dissipation characteristics were compared and evaluated. As a result, while the filler is dispersed in the matrix resin, a part of the matrix resin is replaced with a metal that is liquefied at a temperature that does not deteriorate and decompose the matrix constituent components and is lower than the curing temperature of the matrix resin,
When a composite was formed by forming a cross-linking structure between the fillers so that the fillers were continuously welded to each other by this metal, the thermal conductivity of the composite as a whole was high, and the high thermal conductivity with excellent heat dissipation characteristics. A sex complex could be obtained.
The present invention has been completed based on the above findings.

That is, in the high thermal conductivity composite according to the present invention, the filler is dispersed in the matrix resin, and the low melting point metal or eutectic alloy having a melting point of 500 ° C. or less is used to form a mesh-like metal network. The above-mentioned fillers are continuously welded to each other.

The filler dispersed in the matrix resin may be composed of at least one of metal particles and inorganic particles having a melting point higher than that of the metal forming the metal network.

Furthermore, the thermal conductivity of the inorganic particles is 10 W / m.
Use one that is K or above.

When, for example, an aluminum nitride sintered body powder or an aluminum nitride single crystal body powder is used as the filler, the average particle size is preferably set to 30 μm or less in order to improve the dispersion in the matrix.

As the resin material constituting the matrix of the above composite, a polymer resin having flexibility such as polyvinyl chloride resin, polyethylene, polypropylene, polystyrene, ABS resin, acrylic resin and polyurethane is preferable. Is.

As the filler dispersed in the matrix resin, inorganic particles such as boron nitride, aluminum nitride, silicon carbide and silicon nitride, and metal particles such as copper are used. These fillers are added in a proportion of 40 to 70% by volume with respect to the volume of the composite in order to improve the thermal conductivity of the entire composite. When the added amount is less than 40% by volume, the effect of improving the thermal conductivity is small, while when the added amount exceeds 70% by volume, the ratio of the matrix holding and fixing the filler particles is relatively decreased, and The structural strength of the body is reduced.

On the other hand, the metal mesh formed in the matrix resin in the form of a mesh has a filler such as inorganic particles dispersed in the matrix resin welded to each other to form a continuous heat transfer path, whereby the heat of the entire composite is improved. It is formed to enhance conductivity. This metal network is formed of a low melting point metal having a melting point of 500 ° C. or less or a eutectic alloy thereof in order to prevent decomposition and alteration or hardening of the matrix resin during the production described later. Specific examples of the low melting point metal include Sn (melting point 232 ° C.), Zn (melting point 419 ° C.), P
b (melting point 238 ° C.), In (melting point 156 ° C.), Cd (melting point 321 ° C.), Te (melting point 450 ° C.), Bi (melting point 27)
1 ° C), but Pb and Cd have difficulty in toxicity, and Sn, Z from the viewpoint of safety, versatility, and raw material cost.
An n or Sn-Pb eutectic alloy or the like is preferable.

The metal for forming the metal net is added to the matrix resin together with the filler particles as a metal powder at the raw material stage. The amount of the metal powder added is 50 to 120% by volume based on the filler particles.
If the amount added is less than 50% by volume, it is difficult to form a continuous metal network in the matrix resin, and the effect of improving the thermal conductivity decreases. On the other hand, when the amount added exceeds 120% by volume, the rigidity of the entire composite body is increased, the flexibility is reduced, the adhesion when mounted on the surface of the heating element is reduced, and the heat transfer characteristics are impaired in any case. Will be done. In addition, the thermal conductivity of the whole is lowered.

Further, the metal powder for forming the metal net is arranged in a uniform manner around the particles for filler,
It is desirable that the average particle size be smaller than that of the filler particles, specifically, 20 μm or less, more preferably 1 to 1
It is desirable to set it to about 0 μm.

In a preferred embodiment of the present invention, the fine AlN raw material powder may be added to the matrix resin as it is, but the AlN raw material powder is once compacted and sintered to obtain an AlN sintered body having a high thermal conductivity. The thermal conductivity of the composite can be further increased by adding the AlN sintered powder prepared by crushing the AlN sintered body again as a filler to the composite.

That is, according to the experimental measurement by the inventors of the present application, the AlN raw material powder itself having an average particle size of 0.5 to 1 μm itself retains a low thermal conductivity of about 30 to 40 W / m · K. When an AlN raw material powder is directly dispersed in an acrylic resin to prepare a composite, the thermal conductivity of the composite can be as low as 1.0 to 2.0 W / m · K.

However, once the AlN raw material powder is once sintered as in the present invention, an extremely high thermal conductivity of about 120 to 260 W / m · K is maintained.

The above-mentioned aluminum nitride sintered body, which is a constituent material of the heat dissipation composite, is essentially a material having high thermal conductivity, but various thermal conductivities can be obtained depending on its raw material, sintering conditions and heat treatment conditions. From the characteristics required of the composite, it is desirable to use an AlN sintered body having a high thermal conductivity of generally 150 W / m · K or more, preferably 170 W / m · K or more, since the one having the above can be obtained.

The AlN sintered body as described above is usually manufactured by the following procedure. That is, the average particle size is 0.1 to 5
A compound of Group IIa or Group IIIa of the Periodic Table is added to an aluminum nitride raw material powder of about .mu.m as a sintering aid.
1 to 5% by weight of the mixed powder is molded, and the obtained molded body is sintered at a temperature of 1600 to 1950 ° C. for 2 to 10 hours in a non-oxidizing atmosphere such as N ₂ gas or argon gas. It

In the AlN sintered body thus obtained, there remains an oxide grain boundary phase formed by impurities such as oxygen mixed in the raw material powder, and this grain boundary phase has a thermal conductivity. It seems to be an obstacle.

Therefore, in order to further improve the thermal conductivity of the AlN sintered body, a temperature of 1800 to 1900 ° C. is 2 to 100 in a reducing atmosphere further containing carbon vapor and nitrogen gas.
By performing the heat treatment for about Hr, the AlN sintered body can be highly purified. That is, Al ₅ Y that constituted the grain boundary phase
Oxides such as ₃ O ₁₂ are reduced and nitrided to AlN at a high temperature in an atmosphere in which carbon and nitrogen coexist, while oxygen is combined with carbon and released outside the sintered body. As a result, the oxide of the grain boundary phase that inhibits heat conduction is removed from the AlN sintered body structure, and an AlN sintered body having a high thermal conductivity of about 200 to 260 W / m · K is obtained.

The AlN sintered body thus obtained has a predetermined particle size in a dry pulverizing method, a wet pulverizing method or a pulverizing step in which both are combined by using an ordinary mixing mill such as a ball mill, an attritor or a vibration mill. Is crushed into. The crushed AlN sintered body is classified.

The average particle size of the filler such as the aluminum nitride sintered body powder dispersed in the resin matrix is 30 μm in order to improve the dispersion in the matrix resin.
Set the following. This is because if the average particle size becomes coarse so as to exceed 30 μm, the unevenness of the particle surface becomes large and an air layer that becomes a heat transfer resistance is easily formed.

The average particle size of the AlN sintered body after pulverization is 10 to 10.
It is more preferable to set in the range of 15 μm.

Further, for the purpose of improving the wettability of the filler such as the aluminum nitride sintered body powder obtained by pulverizing as described above with respect to the matrix resin and enhancing the dispersibility, filler particles are mixed in the matrix resin. Before that, it is desirable to carry out a surface modification treatment in advance. As a specific example of the surface modification treatment, 0.1 to 1% by weight of a coupling agent or the like is dropped into a filler such as an aluminum nitride sintered body powder obtained by pulverization and sufficiently mixed. The coupling agent forms a thin coating layer (coating layer) on the surface of each filler particle, and remarkably improves the wettability of the filler particle with the resin. As a result, a composite structure in which the filler particles are uniformly dispersed in the matrix resin can be obtained.

The high thermal conductivity composite body according to the present invention comprises
The volume fraction of the filler of the AlN sintered body powder is 40 to 7
The polymer resin powder is blended so as to be 0%, and the low melting point metal powder for forming the metal net or the eutectic alloy powder thereof is kneaded and blended by 50 to 120% by volume with respect to the filler particles. A raw material mixture is prepared by adding an organic binder and the like, and then the raw material mixture is molded into a predetermined shape by using a press molding method, a doctor blade method, an injection molding method, an extrusion molding method or a roll molding method. After that, the temperature of the entire molded body is raised to a temperature range (200 to 450 ° C.) at which the organic resin component in the molded body is not altered or decomposed, and the temperature is increased to 1 to 5
It is held for a time and then slowly cooled to room temperature to manufacture.

That is, in the heat treatment process of the above-mentioned molded body, the low melting point metal powder or the eutectic alloy powder is melted into a liquid state and forms a network-like crosslinked structure so as to connect the fillers dispersed in the organic resin matrix. To do. When the molded body in which the crosslinked structure is formed is cooled, the liquid metal solidifies while maintaining the crosslinked structure. As a result, a composite structure is obtained in which the filler particles dispersed in the matrix resin are continuously welded through the mesh-shaped metal network.

In the composite having the structure in which the fillers dispersed in the organic resin matrix are connected by the metal net as described above, the metal net having a high thermal conductivity and the filler are continuous from the front surface to the back surface of the composite. Since the heat dissipation path is formed, the thermal conductivity of the entire composite is significantly increased. That is, the heat applied to one surface portion of the composite is efficiently transferred from the filler to the filler through the continuous metal net. At this time, the heat radiation path is hardly affected by the matrix resin having low thermal conductivity. On the other hand, since the resin body and the metal net are excellent in flexibility, the adhesiveness to the heat radiation surface is less likely to be impaired. Therefore, a composite having excellent thermal conductivity can be obtained.

[0037]

According to the high thermal conductivity composite having the above structure, the filler particles dispersed in the resin matrix are connected by the metal net having high thermal conductivity to form a continuous heat dissipation path over the front and back of the composite. Therefore, the thermal conductivity is very large and the flexibility is excellent as compared with the conventional radiator. Therefore, when the heating element and the cooling component are interposed on the joint surface, the thermal resistance between them can be significantly reduced without impairing the adhesion between them, and the heat dissipation characteristics of the heating element can be greatly improved. it can.

[0038]

An embodiment of the present invention will now be described with reference to the accompanying drawings.

Example 1 As a low melting point metal, fine Sn powder particles having an average particle size of 5 μm were added so as to be 90% by volume with respect to boron nitride powder having an average particle size of 25 μm as a filler, and added to this matrix resin. Polyvinyl chloride was added so as to be 20% by weight of the whole composite. Further, dibutyl phthalate (DBP) as a plasticizer was added so as to be 5% by weight with respect to the entire composite to prepare a blended powder. Next, the blended powder was kneaded with a kneader for 3 hours to obtain a raw material mixture 25 having flexibility.

When the cross section of the structure of the raw material mixture 25 was observed with a microscope, a granular structure was observed as shown in FIG. That is, the boron nitride powder 12 as a filler was uniformly dispersed in the polyvinyl chloride resin matrix 11, and the Sn powder 13 as the low melting point metal powder was attached around the boron nitride powder 12.

Next, the raw material mixture 25 was charged into the heating device 20 shown in FIG. 5 to form a composite, and the heat transfer characteristics thereof were measured and evaluated.

Here, as shown in FIG. 5, the heating device 20 surrounds the heat insulating material 2 in order to prevent heat from flowing out to the surroundings.
The plate-shaped heater 22 is provided on the inner bottom of the apparatus main body 20a covered with 1.
Is placed on the upper surface of the plate-shaped heater 22 at a predetermined height (t).
It is configured by arranging a Teflon enclosure 23 and a lid 24.

Then, the raw material mixture 25 is filled in the enclosure 23 of the heating device 20, and the plate-shaped heater 22 installed at the bottom is installed.
To heat the entire raw material mixture 25 to 250 ° C.,
Hold at this temperature for 3 hours.

The particle structure of the raw material mixture 25 during the heating operation is as shown in FIG. 2, and the Sn powder added as the low melting point metal is melted to surround the boron nitride powder 12 in the resin matrix 11 to form a crosslinked structure. The liquefied metal 14 was formed and distributed in a mesh.

Next, a raw material mixture 2 containing the liquefied metal 14
When 5 was cooled to room temperature at a cooling rate of 50 ° C./hour,
A composite 16 having the structure shown in FIG. 3 was obtained. That is, the liquefied Sn metal 14 which was melted in FIG.
As shown in FIG. 3, solidified after cooling, the crosslinked structure was maintained as it was and solidified, and the metal net 15 was formed in the matrix resin 11.

Next, in order to evaluate the heat dissipation characteristics of the obtained composite 16, the plate heater 2 of the heating device 20 shown in FIG.
The composite 16 was placed on the upper surface of No. 2. And the plate heater 2
The set temperature of _No. 2 is fixed at 100 ° C., the surface temperature T ₀ of the plate heater 22 and the surface temperature T ₁ of the upper surface side of the composite body 16 are measured with time, and the temperature difference ΔT (= T ₀ between both surfaces). The results shown in FIG. 4 were obtained for the relationship between −T ₁ ) and time.

Example 2 A fine Sn-Zn eutectic alloy (composition: 85.4 mol% Sn-14.6 mol% Zn powder particles having an average particle diameter of 5 μm as a low-melting point metal was nitrided with an average particle diameter of 25 μm as a filler). It was added to the aluminum sintered body powder in an amount of 90% by volume, and polyvinyl chloride as a matrix resin was added to this in an amount of 20% by weight of the whole composite. DBP) was added so as to be 5% by weight with respect to the entire composite to prepare a blended powder, and then the blended powder was kneaded with a kneader for 3 hours to obtain a raw material mixture having flexibility.

Thereafter, in the same manner as in Example 1, the raw material mixture was poured into the enclosure 23 on the plate-shaped heater 22 of the heating device 20, and the plate-shaped heater 22 was used to heat the entire raw material mixture to 250 ° C.
After heating to 3 hours and holding for 3 hours, it was cooled to room temperature at a cooling rate of 50 ° C./hour to prepare a composite according to Example 2. Then, the obtained composite was subjected to a measurement test of heat dissipation characteristics under the same conditions as in Example 1, and the results shown in FIG. 4 were obtained.

Comparative Example 1 Without adding a low melting point metal powder for forming a metal net, 20% of polyvinyl chloride as a resin matrix and 5% of DBP as a plasticizer were added to boron nitride powder as a filler.
It was added so as to be t% and kneaded with a kneader for 3 hours. In the same manner as in Example 1, the mixture was cast onto a plate heater, the whole device was covered with a heat insulating material, and heat treatment was performed to form a composite. In this state, the plate heater is set to 100 ° C., the surface temperature T ₀ of the plate heater and the surface temperature T ₁ of the upper surface side of the mixture are set.
Was measured and the temperature difference ΔT was observed with respect to time.

Comparative Example 2 Without adding a low melting point metal powder for forming a metal net, 20% of polyvinyl chloride as a resin matrix and 5% by weight of DBP of a plasticizer were added to aluminum nitride powder as a filler. And kneaded in a kneader for 3 hours.

In the same manner as in Example 1, the mixture was cast onto a plate-shaped heater, the whole apparatus was covered with a heat insulating material and heat-treated to form a composite. The plate heater in this state is set to 100 ° C., and the surface temperature T ₀ of the plate heater, the surface temperature T ₁ of the upper surface of the mixture was measured to observe a temperature difference ΔT versus time.

The measurement results of the heat dissipation characteristics of the composites of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in FIG.

As is clear from the results shown in FIG. 4, in the composites according to Examples 1 and 2 in which the low melting point metal was added to form the mesh-shaped metal mesh in the matrix resin, the metal mesh had a heat transfer path. It was confirmed that the heat transfer performance was extremely excellent because it effectively functions as.

On the other hand, in the composites according to Comparative Examples 1 and 2 in which the metal net is not formed, it was found that the heat dissipation characteristics were relatively deteriorated even when the filler having the high thermal conductivity was added.

[0055]

As described above, according to the high thermal conductivity composite of the present invention, the fillers dispersed in the resin matrix are connected by the metal net having high thermal conductivity, and the composite is continuous over the front and back of the composite. Since the heat dissipation path is formed, the heat conductivity is very large and the flexibility is excellent as compared with the conventional heat radiator. Therefore, when the heating element and the cooling component are interposed on the joint surface, the thermal resistance between them can be significantly reduced without impairing the adhesion between them, and the heat dissipation characteristics of the heating element can be greatly improved. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a granular structure in a raw material mixture stage (before heating) of a high thermal conductivity composite according to the present invention.

FIG. 2 is a diagram showing a granular structure during heat treatment of a raw material mixture.

FIG. 3 is a view showing a granular structure of a composite according to the present invention formed by heating a raw material mixture and then cooling it.

FIG. 4 is a diagram showing the heat dissipation characteristics of the high thermal conductivity composite according to the present invention together with a comparative example.

FIG. 5 is a cross-sectional view showing the configuration of a heating device used for heating the raw material mixture and measuring the heat dissipation characteristics of the composite.

FIG. 6 is a sectional view showing a configuration example of a module structure using a conventional radiator.

FIG. 7 is a cross-sectional view showing a state in which a semiconductor package is mounted on a board via a conventional heat dissipation composite.

[Explanation of reference numerals] 1 module structure 2 ceramics substrate 3 semiconductor element (chip) 4 radiating fin 5 resin adhesive 6 heat 7 ceramics multilayer substrate 8 semiconductor package 9 board 10 radiator 11 polyvinyl chloride (matrix resin) 12 boron nitride Powder (filler) 13 Sn powder (low melting point metal) 14 Liquefied metal 15 Metal mesh 16 Composite 20 Heating device 20a Device body 21 Heat insulating material 22 Plate heater 23 Enclosure 24 Lid 25 Raw material mixture

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Katsumi Kuno 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Research & Development Center (72) Inventor Hideo Iwasaki Komukai-Toshiba, Kawasaki-shi, Kanagawa Town No. 1 Incorporated Toshiba Corporation R & D Center (72) Inventor Ryosuke Fujimori No. 1 Komukai Toshiba-cho, Kouki-ku, Kawasaki-shi, Kanagawa Incorporated Toshiba R & D Center

Claims (4)

[Claims] 1. A filler is dispersed in a matrix resin, and the fillers are continuously welded to each other through a metal mesh formed in a mesh shape by a low melting point metal or a eutectic alloy having a melting point of 500 ° C. or less. A highly heat-conductive composite characterized by being 2. A high thermal conductivity composite, wherein the filler dispersed in the matrix resin is at least one of metal particles and inorganic particles having a melting point higher than that of the metal forming the metal network. 3. The high thermal conductivity composite according to claim 2, wherein the inorganic particles have a thermal conductivity of 10 W / m · K or more. 4. The high thermal conductive composite according to claim 2, wherein the inorganic particles are at least one of an aluminum nitride sintered body powder and an aluminum nitride single crystal body powder, and have an average particle size of 30 μm or less. .