JP2010021165A - Phase-changing heat dissipating member - Google Patents

Abstract

【Task】
To provide a phase change type heat radiating member suitable for a heat radiating material of an electronic component having low heat resistance and excellent workability.
[Solution]
An organic component containing a resin that softens at 30 to 120 ° C. is 15 to 35% by mass, a powder a having an average particle size of 0.3 to 0.8 μm, and a powder b having an average particle size of 0.9 to 1.9 μm, A Vickers hardness of 24 Hv is provided on at least one surface of a layer made of a thermally conductive resin composition containing 65 to 90% by mass of an inorganic filler having a volume ratio of a / b = 7/3 to 3/7. A phase change type heat radiating member characterized in that the following metal layers are laminated, and the powder a and the powder b are aluminum nitride and / or alumina powder and / or zinc oxide powder. The above-mentioned phase change type heat radiating member, wherein the metal layer is tin or indium or an alloy containing at least one of them.
[Selection figure] None

Description

  The present invention relates to a phase change type heat radiation member suitable as a heat radiation material for electronic components.

  With the recent high integration of electronic circuits, the problem of heat dissipation, which is how to release heat generated from the circuit to the outside, has become serious. As countermeasures, a heat dissipation sheet made of a cured product in which silicone rubber is filled with a thermally conductive inorganic powder, a heat dissipation spacer made of a cured product having flexibility in which a silicone gel is filled with a thermally conductive inorganic powder, and heat is applied to liquid silicone. Examples include fluid heat-dissipating grease filled with conductive inorganic powder, phase-change heat-dissipating members using phase change of resin, and the like. Of these, those that can be easily thinned are grease and phase change type heat radiating members, but phase change is preferred in terms of workability.

However, when further improvement in workability is required or when it is reused repeatedly, it is used in a form in which at least one surface thereof has a high thermal conductivity and is not sticky, specifically a metal foil laminated. May be. In that case, aluminum and copper are often used from the viewpoint of thermal conductivity (Patent Document 1), but the heat dissipation characteristics as a laminate deteriorate due to the contact resistance between the phase change layer and the metal foil layer. There was a problem.
JP 2004-75760 A

  In view of the above, an object of the present invention is to provide a phase change type heat radiating member suitable for a heat radiating material for electronic parts, which has high thermal conductivity and excellent workability, and does not deteriorate characteristics even when repeatedly used. is there.

That is, in the present invention, the organic component containing a resin softening at 30 to 120 ° C. is 15 to 35% by mass, the powder a having an average particle size of 0.3 to 0.8 μm, and the average particle size of 0.9 to 1.9 μm. And at least one surface of a layer made of a thermally conductive resin composition containing 65 to 90% by mass of an inorganic filler having a volume ratio of a / b = 7/3 to 3/7. A phase change type heat dissipating member, wherein a metal layer having a Vickers hardness of 24 Hv or less is laminated. Further, the present invention is the above-described phase change type heat radiating member, wherein the powder a is alumina powder and / or zinc oxide, and the powder b is aluminum nitride powder. Furthermore, the present invention is the above-described phase change type heat radiating member, wherein the metal layer is tin or indium or an alloy containing at least one of them.

According to the present invention, the inorganic filler in the heat conductive resin composition layer (hereinafter referred to as a phase change layer) is set to a predetermined amount, and further by controlling the hardness of the metal foil laminated on the phase change layer, Effects such as heat dissipation, good workability, and prevention of characteristic deterioration during repeated use can be achieved.

  In the present invention, high heat dissipation characteristics can be obtained by using a metal foil laminated on the phase change layer having a Vickers hardness of 24 or less, specifically, tin or indium. This is considered to be because the softness enhances the contact between the inorganic material in the organic bonding layer when a load is applied and reduces the thermal resistance at the interface between the organic-inorganic mixed layer and the metal foil. . When the hardness of the metal foil is high, the resistance of this portion increases, and even if a material having high thermal conductivity such as copper is used, the heat dissipation characteristics are deteriorated.

  In the present invention, the powder a and the powder b are preferably aluminum nitride powder and / or alumina powder and / or zinc oxide powder and / or metal aluminum powder. More preferably, zinc oxide powder and aluminum nitride powder are used for powder a, and aluminum nitride powder is used for powder b. Thereby, high heat conductivity, high filling property, and fluidity can be combined. In addition, one or two or more kinds of powders selected from silicon carbide, silicon nitride, boron nitride and the like may be contained up to 10% by mass in the total of the inorganic fillers including powders a and b.

  As the filler, two or more kinds of powders having different average particle diameters are used. That is, the powder a having an average particle size of 0.3 to 0.8 μm and the powder b having an average particle size of 0.9 to 1.9 μm have a volume ratio of a / b = 7/3 to 3/7. Used for. At this time, each of the powder a and the powder b may be composed of a plurality of powders. This improves the fluidity of the phase change layer of the present invention and also improves the contact with the metal layer when a load is applied. When the average particle size of the powder a is 0.3 μm or less, filling becomes difficult, and the fluidity is lowered, making it difficult to thin the phase change layer. On the other hand, when the average particle size of the powder b exceeds 1.9 μm, the phase change layer may undergo some alteration when repeatedly used, and the heat dissipation characteristics may deteriorate. In this specification, the average particle size is a particle size distribution calculated from the data of the light intensity distribution of the diffracted / scattered light by the particles detected by a sensor using a laser diffraction particle size distribution measuring device. The volume average particle size obtained by multiplying the value of the particle size by the relative particle amount (difference%) and dividing by the sum of the relative particle amounts (100%).

  The content rate of a filler shall be 65-90 mass% in a phase change layer structure. If it is less than 65% by mass, the thermal conductivity is low, and it is difficult to reduce the thermal resistance no matter how thin it is. Moreover, when it exceeds 90 mass%, the fluidity | liquidity of a phase change layer will become low and it will become difficult to thin.

  As the powders a and b, those having high thermal conductivity are preferable, and in this sense, various metal powders and ceramic powders are preferable. However, considering the cost, thermal conductivity characteristics, safety, etc., the powder a has high moisture resistance reliability. Alumina powder and / or zinc oxide is particularly preferable, and the powder b is particularly preferably aluminum nitride powder having high thermal conductivity. In other cases, metal powder such as metal aluminum can also be used. In this case, although the thermal conductivity is high, the powder becomes very active due to the metal fine powder, and handling such as increased risk of explosion. It becomes difficult.

The organic component of the phase change layer of the present invention preferably contains an organic component that softens at a temperature of 30 to 120 ° C. If the softening temperature is less than 30 ° C., it tends to soften even at room temperature and hinders handling. On the other hand, in order to soften above 120 ° C., a very high temperature is required, which is not preferable. Examples of such resins include polyethylene, polypropylene, ethylene-α olefin copolymers, thermoplastic resins such as ethylene-vinyl acetate copolymers, and other materials that are solid at room temperature and become a low-viscosity fluid upon heating, for example, Examples thereof include waxes such as microcrystalline wax, montanic acid wax, and montanic acid ester wax, and paraffin wax that is solid at room temperature. One or more of these, and liquid paraffin are added as appropriate. By constituting the matrix with such an organic component, the fluidity at the time of heating can be made extremely high and the thinning can be facilitated, so that the thermal resistance can be reduced.

In the phase change layer of the present invention, in addition to the above as an organic component, for example, a pressure-sensitive adhesive for imparting tackiness, a dispersant for improving dispersibility of inorganic fillers, a surfactant, a coupling agent, etc. Various additives may be used as appropriate.

The phase change layer composition of the present invention can be produced by kneading the above materials with a universal mixing stirrer, a kneader or the like while heating them, and forming a sheet to a thickness of 0.01 mm to 0.5 mm. If the thickness exceeds 0.5 mm, it is difficult to reduce the thermal resistance. On the other hand, if it is less than 0.01 mm, it becomes difficult to follow the unevenness of the heat-generating electronic component, so that the contact becomes insufficient and the thermal resistance increases.

In the sheet molding, the phase change layer is placed on a foil of metal tin, metal indium or the like and heated and pressed with a mold having a predetermined thickness, or is passed through a predetermined space with a roll coater or the like while being heated. The change layer can be dissolved by a solvent such as toluene, applied by a doctor blade method, etc., and then adjusted by a laminator. The thickness of the foil is preferably 0.005 to 0.2 mm. If it is less than 0.005 mm, it is difficult to handle and wrinkles easily, and if it exceeds 0.2 mm, the flexibility is lowered.

The phase change type heat radiating member of the present invention is used to transfer heat from heat generating electronic parts such as MPU, power transistor and transformer to heat radiating parts such as heat radiating fins and heat radiating fans. Used by being sandwiched between parts. As a result, heat transfer between the heat-generating electronic component and the heat-dissipating component is improved, and malfunction of the heat-generating electronic component can be significantly reduced.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

Examples 1-7
As powder a, commercially available alumina (AA-05 average particle size 0.5 μm manufactured by Sumitomo Chemical Co., Ltd.), zinc oxide powder (“Class 1” average particle size 0.6 μm manufactured by Sakai Chemical Co., Ltd.), and powder b, Commercially available aluminum nitride powder (“H grade” manufactured by Tokuyama Corporation; average particle diameter of 1.6 μm) was used, and these were mixed at a ratio shown in Table 1 to prepare an inorganic filler. The average particle diameter was evaluated with a laser diffraction particle size distribution measuring apparatus (Microtrack MT3200 manufactured by Nikkiso Co., Ltd.).

On the other hand, liquid paraffin (“Moleco White P-350P” manufactured by Matsumura Oil Co., Ltd.), ethylene-vinyl acetate copolymer (EVA) (“Ultrasen 725” manufactured by Tosoh Corp.), hot melt adhesive (Matsumura Oil Co., Ltd.) "Molescommelt TN-530S") was prepared, blended together with inorganic fillers in the proportions shown in Table 1, placed in a universal mixing stirrer container heated to 150 ° C, vacuum degassed while mixing for 15 minutes, and cooled Then, it was taken out to obtain a phase change layer composition.

This phase change layer composition is placed on a metal tin foil (made by Nippon Foil Co., Ltd., Vickers hardness 20 Hv) or indium foil (made by Nippon Foil Co., Ltd., Vickers hardness 16 Hv) having a thickness of 0.02 mm and a width of 160 mm, and 120 After heating through a far-infrared heating furnace set at 0 ° C. to melt the flowable resin, a silicone-treated surface of a one-side silicone-treated PET film having a thickness of 0.1 mm and a width of 160 mm is formed on the upper surface. They were placed in contact with each other and passed through a comma coater with a 0.2 mm gap. This was cut to a length of 400 mm and then cooled, and the PET film was peeled off to obtain a phase change type heat radiation member having a thickness of 0.1 mm, a width of 150 mm, and a length of 400 mm.

The thermal resistance of the obtained phase change type heat radiating member was set with a load of 4.2 kg between a copper jig with a 10 mm square sample mounting portion and a copper cooling jig embedded with a heater. Thereafter, the heater was applied with electric power of 20 W and held for 30 minutes, and the temperature difference (° C.) generated in the sandwiched heat radiation member portion was measured. This was allowed to cool to room temperature, the phase change type heat radiating member was once removed, then set again, and the measurement was performed with the load and power applied in the same manner. This operation was repeated, and a total of five measurements were performed. The thermal resistance value was calculated by the formula: thermal resistance (° C./W)=temperature difference (° C.) / Power (W). Table 1 shows the results of the first and fifth measurements, respectively.

Comparative Examples 1-2
A phase change type heat radiating member was produced according to Example 1 except that aluminum (Vickers hardness 25 Hv) and copper (Vickers hardness 46 Hv) were used as the metal foil. The obtained thermal resistance values were as shown in Table 1, showing a higher thermal resistance value than the Examples.

Comparative Example 3
Commercially available alumina (AA-05 average particle size 0.5 μm manufactured by Sumitomo Chemical Co., Ltd.) was used as powder a, and commercially available metal aluminum powder (# 800 manufactured by Minerco, average particle size 2.5 μm) was used as powder b. A phase change type heat radiating member was manufactured according to Example 1 except for the above. What was obtained showed a high thermal resistance value in the measurement results of the fifth repetition compared to Examples 1-7.

Comparative Examples 4 and 5
A phase change type heat radiating member was produced in the same manner as in Example 1 except that the ratio of the organic component was changed to the composition shown in Table 1 outside the scope of the present invention. What was obtained showed a high thermal resistance value compared to the Examples (Comparative Example 4) or was too poor to be formed into a sheet (Comparative Example 5).

The phase change type heat radiating member of the present invention can be applied to all heat radiating applications such as various electronic parts that generate heat.

Claims (6)

10 to 35% by mass of an organic component containing a resin that softens at 30 to 120 ° C., a powder a having an average particle size of 0.3 to 0.8 μm, and a powder b having an average particle size of 0.9 to 1.9 μm, a / b
= Vickers hardness is 24 Hv or less on at least one surface of a layer made of a thermally conductive resin composition containing 65 to 90% by mass of an inorganic filler having a volume ratio of 7/3 to 3/7. A phase change type heat dissipating member, wherein a metal layer is laminated. The phase change type heat radiation member according to claim 1, wherein the powder a is alumina powder and / or zinc oxide powder. The phase change type heat radiation member according to claim 1, wherein the powder b is an aluminum nitride powder. The phase change type heat radiation member according to any one of claims 1 to 3, wherein the metal layer is tin or indium or an alloy containing at least one of them. The thickness of a metal layer is 0.005-0.2 mm, The phase change type thermal radiation member as described in any one of Claims 1-4 characterized by the above-mentioned. The thickness of the layer which consists of a heat conductive resin composition is 0.01-0.5 mm, The phase change type thermal radiation member as described in any one of Claims 1-5 characterized by the above-mentioned.