JP2005228955A - Heat dissipation member, its manufacturing method and application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat dissipation member excellent in shape followability and different from paste, and also to provide its manufacturing method and an electronic apparatus incorporating it. <P>SOLUTION: In the heat dissipation member, a silicone layer having E type hardness by JIS K 6253 is ≤65. The layer E and an adhesive thermoplastic resin layer are stacked one on the other putting a metal foil therebetween, and its heat conductivity is ≥2.0 W/mK. After two layers of the metal foil and the silicone layer are manufactured, the adhesive thermoplastic resin layer is formed on an aluminum foil surface on the opposite side where no silicone layer is existent. The electronic apparatus is characterized in that a silicone layer side is adapted to face a heat developable electronic component and an adhesive thermoplastic resin layer side adapted to face a heatsink to incorporate the heat dissipation member. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a heat radiating member, a manufacturing method thereof, and an application.

Conventionally, when attaching electronic parts with large heat generation such as power transistors and power modules to heat sinks such as heat radiating fins, heat dissipation members are used to eliminate gaps and efficiently transfer heat generated in electronic parts to heat sinks Has been. Examples of the heat radiating member include a paste in which a heat conductive inorganic powder is mixed in silicone grease (Patent Document 1), and a sheet in which a heat conductive powder such as alumina, boron nitride, aluminum nitride is mixed in silicone rubber (Patent Document). 2) is known.
JP 2000-63873 A Japanese Patent No. 3434678

However, the paste requires a coating operation, and has a drawback that the paste flows out with time after coating. In the sheet, since there is no coating operation, the process is not complicated, but the shape following property is poor, so that the effect of eliminating the gap between the parts is small.

An object of the present invention is to provide a heat dissipating member that is excellent in shape followability and different from a paste, a manufacturing method thereof, and an electronic apparatus in which the heat dissipating member is incorporated.

That is, according to the present invention, a silicone layer having an E-type hardness of 65 or less according to JIS K6253 and an adhesive thermoplastic resin layer are laminated with a metal foil interposed therebetween, and the thermal conductivity is 2.0 W / mK or more. There is a heat radiating member. In this case, it is preferable that the thermal conductivity and thickness of the silicone layer are larger than the thermal conductivity and thickness of the adhesive thermoplastic resin layer. Moreover, it is preferable that the adhesive force of an adhesive thermoplastic resin layer is 0.5 N / 25mm or more as a value with respect to an aluminum plate.

According to the present invention, a heat radiating member is characterized in that after manufacturing a two-layer body of a metal foil and a silicone layer, an adhesive thermoplastic resin layer is formed on the opposite metal foil surface not having the silicone layer. It is a manufacturing method. Furthermore, the present invention provides an electronic device comprising any one of the above heat dissipation members with the silicone layer side in contact with the heat-generating electronic component and the adhesive thermoplastic resin layer side in contact with the heat sink. is there.

ADVANTAGE OF THE INVENTION According to this invention, the thermal radiation member different from the paste excellent in the shape followability, and its manufacturing method are provided. In addition, an electronic device such as a power module having excellent heat dissipation characteristics is provided.

As the silicone resin used for the silicone layer of the present invention, those imparted with flame retardancy are suitable, and as an example of a commercially available product, a trade name “silicone gel XE14” manufactured by GE Toshiba Silicone Co., Ltd. -B1057 ", trade names" silicone gel SE1886 "," silicone gel SE1885 "manufactured by Toray Dow Corning Silicone Co., etc.

Examples of the heat conductive material used to make the silicone layer thermally conductive include metals such as aluminum, copper, and silver, metal oxides such as alumina, magnesia, and silica, aluminum nitride, silicon nitride, and nitride. One or more selected from nitrides such as boron, carbides such as graphite and boron carbide, and the like. Their shape is not limited, for example, powder, fiber, needle, scale, or sphere. For example, commercial products of thermal conductive materials are trade names “Aluminum Nitride Powder R15KS”, “Aluminum Powder AC1003”, “Aluminum Powder AC2500” manufactured by Toyo Aluminum Co., Ltd., “Spherical Alumina DAM45” manufactured by Denki Kagaku Kogyo, Sumitomo The product names “Alumina AA05”, “AA2”, etc. manufactured by Kagakusha.

These thermally conductive substances preferably contain 70 to 95% by mass, particularly 80 to 90% by mass in the silicone layer. Thereby, the thermal conductivity of the silicone layer can be secured at 2.0 W / mK or more. Also, by adjusting the degree of cure of the silicone layer, the E-type hardness according to JIS K6253 can be made 65 or less. If the E-type hardness of the silicone layer exceeds 65, the shape followability of the heat dissipating member deteriorates, so that it becomes difficult to sufficiently fill the gap between the two even when directly contacting a heat-generating electronic component such as a semiconductor chip. Cannot be transmitted smoothly. Further, for example, in a ball grid array type chip that is weak against a load, there is a possibility that a soldered part may be peeled off or the chip itself may be destroyed.

The adhesive thermoplastic resin layer contains a thermoplastic resin and a tackifier as essential components. As the thermoplastic resin, for example, one or more selected from ethylene resins, propylene resins, ethylene-α-olefin copolymers, ethylene-vinyl acetate copolymers, and the like can be used. Examples of the tackifier include, as natural products and derivatives thereof, gum rosin, tall oil rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, rosin glycerin ester, hydrogenated rosin pentaerythritol ester, and the like. As the synthetic resin, petroleum resin, hydrogenated petroleum resin, coumarone / indene resin, styrene resin, phenol resin, xylene resin and the like can be used.

The adhesive strength of the thermoplastic resin layer is such that when the adhesive thermoplastic resin layer is incorporated in direct contact with a heat sink such as a heat radiating fin, it is attached to an aluminum plate and packaged to prevent displacement. In order to prevent peeling off due to vibration during storage or transportation, the adhesive strength to the aluminum plate is preferably 0.5 N / 25 mm or more. This adhesive force can be adjusted with the usage-amount of a tackifier, The measurement can be performed according to the measurement of 90 degree peeling adhesive force of JISZ0237 "adhesive tape * adhesive sheet test method".

In order to make the adhesive thermoplastic resin layer thermally conductive, the above-mentioned thermally conductive substance is preferably contained in the adhesive thermoplastic resin layer in an amount of 60 to 90% by mass, particularly 70 to 85% by mass. When the content of the heat conductive substance is remarkably increased, the adhesive strength becomes insufficient, and when it is remarkably lowered, the heat conductivity is insufficient.

The metal foil used in the present invention is a highly heat conductive metal foil such as a copper foil, an aluminum foil, an alloy foil or a clad foil thereof. The thickness of the metal foil is preferably 0.2 mm or less, particularly 0.01 to 0.05 mm, in order to improve the shape followability. Among them, aluminum foils such as “Soft Aluminum A1N20H-O” and “Soft Aluminum A1N30H-O” manufactured by Nippon Foil Co., Ltd. are preferable.

The heat conductivity of the heat dissipating member of the present invention is 2 W / mK or more in consideration of imparting good heat dissipating property of the electronic device. In particular, the thermal conductivity of the silicone layer is preferably larger than that of the adhesive thermoplastic resin layer, and among them, the thermal conductivity of the adhesive thermoplastic resin layer is preferably 1.5 W / mK or more.

If an example of the whole dimension of the heat radiating member of this invention is shown, it will be a sheet form of 10-50 mm x 10-50 mm x thickness 0.5-3 mm. Especially, the thickness of the silicone layer is made thicker than the thickness of the adhesive thermoplastic resin layer, in particular, the thickness of the silicone layer is 1.5 to 20 times, more preferably 5 to 15 times, the thickness of the adhesive thermoplastic resin layer. By increasing the thickness, sufficient adhesive force and high flexibility can be provided.

The manufacturing method of the heat radiating member of the present invention is as follows. First, after forming a two-layer body by forming a silicone layer on one surface of a metal foil, an adhesive thermoplastic resin layer is formed on the opposite metal foil surface on which the silicone layer is not formed. Is a method of forming

The two-layered body is, for example, a mixture of a silicone resin, a curing agent thereof, and a heat conductive material, and a gel-like silicone by further mixing a flame retardant imparting agent such as a crosslinking agent or chloroplatinic acid as necessary. It can be manufactured by preparing a resin composition, laminating it on one side of a metal foil by a doctor blade method, an extrusion method or the like, and then heating and crosslinking at a temperature of 120 to 170 ° C.

Further, in order to form an adhesive thermoplastic resin layer on a metal foil surface on which a silicone layer is not formed, for example, a laminate method in which an adhesive thermoplastic resin molded article is individually manufactured and pasted, adhesive thermoplasticity Dissolve the resin layer in an organic solvent such as toluene, coat it on the surface of the metal foil with a coater such as a doctor, volatilize the solvent, and then heat the roller part above the softening point of the adhesive thermoplastic resin. It can be carried out by a method of developing adhesiveness by passing a laminator. An adhesive thermoplastic resin molding can be produced, for example, by mixing and kneading various additives and heat conductive powder at a temperature equal to or higher than the softening point of the thermoplastic resin, and then passing the kneaded product through a heating laminator. it can.

The electronic device of the present invention is constructed by incorporating the heat radiating member of the present invention with the silicone layer side in contact with a heat-generating electronic component and the adhesive thermoplastic resin layer side in contact with a heat sink. For example, the heat-generating electronic component is positioned substantially at the center of the heat dissipating member, and the adhesive thermoplastic resin layer side of the heat dissipating member is attached to the heat sink. The heat sink is mounted so that a large load is not applied to the chip using a screw spring or a plate spring for fixing.

There are no restrictions on heat-generating electronic components and heat sinks used in the present invention. As the heat generating electronic component, for example, a module such as a switching power supply or a drive circuit for home appliances, a chip such as an ASIC used for image processing, television, audio, or the like, a CPU of a personal computer, or the like is used. In addition, as the heat sink, for example, a housing, a structural member made of aluminum, an aluminum plate, an aluminum radiating fin, a radiating fin with a forced cooling unit such as a metal or alloy heat spreader, a radiator or the like is used. .

Examples 1-8 Comparative Examples 1-11
The following materials were prepared.
(1) Silicone resin: GE Toshiba Silicone product name “XE14-B1057”
(2) Silicone oil: Trade name “KF96-100CS” manufactured by Shin-Etsu Chemical Co., Ltd.
(3) EVA: Trade name “EV210” manufactured by Mitsui DuPont Polychemical Co., Ltd.
(4) Polybutene: Idemitsu Petrochemical's trade name “Idemitsu Polybutene 15R”
(5) Tackifier (hydrogenated petroleum resin): trade name “ESCOREZ2520” manufactured by ExxonMobil
(6) Aluminum nitride powder: Toyo Aluminum Co., Ltd. trade name “R15KS”, average particle size 15 μm
(7) Alumina powder A: trade name “DAM45” manufactured by Denki Kagaku Kogyo, average particle size of 20 μm
(8) Alumina powder B: trade name “AA2” manufactured by Sumitomo Chemical Co., Ltd., average particle diameter: 2 μm
(9) Alumina powder C: trade name “AA05” manufactured by Sumitomo Chemical Co., Ltd., average particle size 0.5 μm
(10) Aluminum powder: trade name “AC2500” manufactured by Toyo Aluminum Co., Ltd., average particle size 15 μm

The said material was mixed in the ratio shown in Table 1, and the mixture for silicone layer formation and the mixture for adhesive thermoplastic resin layer formation were prepared. Next, the silicone layer A to D forming mixture was laminated by changing the thickness on one side of a 0.03 mm thick aluminum foil (trade name “Soft Aluminum A1N30H-O” manufactured by Nihon Foil Co., Ltd.) by the doctor blade method. Then, it was heated and crosslinked at a temperature of 150 ° C. to produce a two-layer body of a silicone layer and an aluminum foil. Since the mixture for forming the silicone layer E has a high viscosity, it was press-molded into a sheet shape, and then an aluminum foil was laminated, pressed again and adhered, and heated and crosslinked at a temperature of 150 ° C. to produce a two-layer body. The obtained two-layer silicone layer was measured for thermal conductivity, JIS hardness (E type), and adhesive strength. The results are shown in Table 2.

Next, the adhesive thermoplastic resin layer-forming mixture was sandwiched between two PET resin separators, and heated and pressurized to produce a sheet-like or film-like molded body. The obtained molded product was measured for thermal conductivity, JIS hardness (E type) and adhesive strength. The results are shown in Table 3. This molded body is laminated on the opposite aluminum foil surface that does not have the two-layered silicone layer produced above, and then laminated to produce various heat radiating members (see FIG. 1). Was measured. The results are shown in Table 4.

(1) Thermal conductivity: a thermal conductivity test piece having a thickness of 1 mm and a 25 mm square (20 mm or more on one side) with respect to a heat radiation member in which a silicone layer or a thermoplastic resin layer or both layers are laminated via an aluminum foil. This was sandwiched between two 20 mm square copper blocks from above and below, and a 7 kgf weight was placed on the upper block with a heat insulating material sandwiched between them. The copper block on one side has a built-in heater, and the cooling unit is mounted on the other side. After applying a power of 20 W to the heater for 30 minutes, the temperature difference (° C.) between the heat flux (W) between the two copper blocks and the upper and lower connecting portions of the thermal conductivity test piece is calculated, and the thermal resistance (° C./W ) Subsequently, the thermal conductivity was calculated from the thickness of the sample piece and the heat transfer area (20 mm square) at the time of mounting.
(2) JIS hardness (E type): A hardness test piece having a thickness of about 12 mm was prepared for the silicone layer or the thermoplastic resin layer, and a plurality of heat dissipation members having a thickness of about 12 mm were used as the hardness test piece. . Measured according to JIS K6253 “Testing method for hardness of vulcanized rubber and thermoplastic rubber”.
(3) Adhesive strength: For each of the silicone layer or the thermoplastic resin layer, a 25 mm wide adhesive strength test piece was prepared, and the 90 ° peel adhesive strength measurement method of JIS Z0237 “Adhesive tape / adhesive sheet test method” was used. In conformity, the adhesive strength to the aluminum plate was measured.
(4) Mounting state: A test piece of 20 mm square was prepared for the structure shown in Table 4, and this was mounted in the approximate center of a 40 mm square aluminum plate. The test piece was mounted by applying a load of 0.1 MPa at 20 ° C. for 15 seconds. When there was adhesion on the surface to which the load was applied, the load was applied with a separate film (Takaline Corporation product name “BY-13”) as necessary. The single-layered test pieces of Comparative Examples 2 to 4 are mounted as they are because there is no distinction between the front and back sides, and the other layer (here, the thermoplastic resin layer or the aluminum foil layer) is an aluminum plate. It was attached so as to be in contact with. The aluminum plate on which the test piece was mounted was naturally dropped from a height of 900 mm, and the drop of the test piece was confirmed. The test piece was dropped 12 times in total, 3 times on each of the surface on which the test piece was mounted and on the opposite surface, side, and corner, and the test piece was peeled off even once.

As can be seen from the comparison of Table 2, Table 3, and Table 4, the single silicone layer has flexibility but lacks adhesive strength, and the single adhesive thermoplastic resin layer has adhesive strength but lacks flexibility. To do. On the other hand, the heat radiating member of the present invention (Example of Table 4) shows characteristics that cannot be obtained by each of the silicone layer and the adhesive thermoplastic resin layer, and due to the adhesive strength of the thermoplastic resin layer, It is possible to provide a heat dissipating member different from paste and a method of manufacturing the heat dissipating member, which can be reliably attached to a heat dissipating fin and the like, and has excellent shape followability due to the flexibility of the silicone layer.

When the heat dissipation member obtained in Examples 1 to 8 of the present invention was subjected to a heat dissipation test using a power circuit of a digital device, the mounting operation of the heat dissipation member to the heatsink was easy, the mounting state was stable, and peeling There was no worry about falling. When the power was turned on after the heat sink was screwed, the surface temperature of the chip on the circuit was 63 ° C. in the absence of the heat radiating member, whereas it was 42 ° C. due to the mounting of the heat sink and the heat radiating member. In addition, when the heat radiating member was screwed to the heat sink, it absorbed the load to such an extent that the heat-generating electronic component did not deform, so that it was not damaged and the digital device operated stably.

  The heat dissipating member of the present invention is used as a heat dissipating member for various heat-generating electronic components of power supply circuits and digital devices, sandwiched between a heat sink and the heat-generating electronic components. Examples of the electronic device of the present invention include a switching power supply, a DVD recorder called a digital home appliance, a digital TV, a video camera, and the like.

Explanatory drawing which shows an example of the electronic device manufactured in the Example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat sink 2 Heat radiating member 21 Adhesive thermoplastic resin layer 22 Aluminum foil 23 Silicone layer 3 Heat generating electronic component

Claims (5)

A silicone layer having an E-type hardness of 65 or less according to JIS K6253 and an adhesive thermoplastic resin layer are laminated with a metal foil interposed therebetween, and the thermal conductivity is 2.0 W / mK or more. Heat dissipation member. 2. The heat radiating member according to claim 1, wherein the silicone layer has a thermal conductivity and a thickness that are both greater than the thermal conductivity and the thickness of the adhesive thermoplastic resin layer. The heat radiating member according to claim 1 or 2, wherein the adhesive strength of the adhesive thermoplastic resin layer is 0.5 N / 25 mm or more as a value with respect to the aluminum plate. A method for producing a heat radiating member, comprising: producing a two-layer body of a metal foil and a silicone layer, and then forming an adhesive thermoplastic resin layer on the opposite metal foil surface not having the silicone layer. An electronic device comprising the heat dissipation member according to any one of claims 1 to 3, wherein the silicone layer side is in contact with the heat-generating electronic component and the adhesive thermoplastic resin layer side is in contact with the heat sink.

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