JPH1119948A - Manufacture of radiation member for electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a radiation member for electronic parts which exhibits extremely high thermal conductivity and flexibility with a low boron nitride content by a method in which rubber green sheets containing boron nitride powder are molded, laminated, and vulcanized, and the laminate is cut in the lamination direction in a desired thickness. SOLUTION: A radiation member for electronic parts is produced by a method in which an addition reaction type liquid silicone is mixed with boron nitride powder at room temperature into slurry, the slurry is extruded by an extruder of a piston-type or another to be molded provisionally into green sheets, which are laminated and cured by heating, and the laminate is cut from the lamination direction in a desired thickness. The laminate of the green sheets, after being cut in the lamination direction in a desired thickness, is vulcanized. The resulting radiation member is inserted between exothermic electronic parts or a circuit board on which the parts are mounted and a cooling device. It is also possible that the member, for example, is stuck to the cooling device in advance to be integrated and is supplied.

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 member for electronic parts having excellent thermal conductivity and flexibility.

[0002]

2. Description of the Related Art In heat-generating electronic components such as transistors and thyristors, it is important to remove heat generated during use. Conventionally, as such a heat removal method, a heat-generating electronic component has been generally attached to a heat-dissipating fin or a metal plate via an electrically insulating heat-dissipating sheet to dissipate heat. Is used in which a thermally conductive filler is dispersed in silicone rubber.

[0003] In recent years, the amount of heat generated by circuits in electronic components has been increasing with the increase in the degree of integration thereof, and a heat radiation sheet having higher thermal conductivity than ever has been required. In view of the above, applying a strong mounting load is evaded, and in such a case, a sheet-shaped heat radiation member having extremely low thermal resistance and high flexibility has been required.

[0004] From the viewpoint of reducing the thermal resistance of the heat radiating sheet, attention has been paid to a filler having a high thermal conductivity. In particular, boron nitride has the specificity of having extremely high thermal conductivity in the length direction of the flaky particles, and therefore, attempts have been made to use boron nitride particles in an upright state. For example, JP-A-8-
Japanese Patent No. 244094 discloses that 50% by volume or 60% by volume of boron nitride
And 0.20 ° C./W (0.3 mm
It is shown that a sheet having a thermal resistance of 0.12 ° C./W (thickness: 0.3 mm) can be obtained.
Japanese Patent Publication No. JP-A No. 9-64139 contains 39% by volume or 56% by volume of boron nitride, and is 0.41 ° C./W (0.5 mm thick), respectively.
It is described that a heat resistance of 0.30 ° C./W (0.5 mm thickness) can be obtained.

Further, as an attempt to randomly orient boron nitride, Japanese Patent Laid-Open Publication No. Sho 62-154410 discloses that a sheet containing 46 to 56% by volume of boron nitride has a heat resistance of at least 0.40 ° C. / It is shown that W (0.45 mm thickness) could be reduced.

[0006]

However, all of the above methods involve a large amount of boron nitride powder, which not only increases the cost, but also has the problem of high thermal conductivity but insufficient flexibility. There is.

An object of the present invention has been made in view of the above, and it is an object of the present invention to provide a method of manufacturing a heat-dissipating member for electronic parts, which exhibits a very high thermal conductivity and flexibility with a low boron nitride content. .

[0008]

That is, the present invention relates to a method for forming a rubber green sheet containing a boron nitride powder, laminating a plurality of the green sheets, vulcanizing and curing, and cutting the green sheet into a desired thickness in the laminating direction. Or a method of manufacturing a heat radiating member for an electronic component, which comprises laminating a plurality of sheets and cutting the laminate to a desired thickness in a laminating direction, followed by vulcanization and curing. Alternatively, the present invention provides a method for manufacturing a heat radiating member for an electronic component, which is made of a different material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The boron nitride powder used in the present invention can be produced by coexisting a boron-containing compound and a nitrogen-containing compound, calcining the mixture, and then pulverizing the mixture. Graphite index (G
It is desirable that the high crystallinity I) is 1.5 or less.

Further, in the present invention, aluminum nitride, silicon nitride, alumina,
Silicon carbide, a thermally conductive filler other than boron nitride such as beryllia can be used in combination, and further, aluminum, copper,
It can be used in combination with a metal powder such as silver.

The heat dissipation member for electronic parts of the present invention has a boron nitride powder content of 20 to 45% by volume, particularly 25
Desirably, it is 40% by volume. If the content of the boron nitride powder is less than 20% by volume, the heat resistance as a heat radiating member for electronic components is not sufficient, and if it exceeds 45% by volume,
Flexibility and mechanical strength are impaired.

The rubber used as the matrix in the present invention includes rubber-based materials such as silicone rubber, urethane rubber, acrylic rubber, butyl rubber, ethylene propylene copolymer and ethylene vinyl acetate copolymer. Among them, silicone rubber is particularly suitable because it is excellent in flexibility, shape followability, adhesion to a heat generating surface, and heat resistance when formed into a molded product.

As a type of the silicone rubber, a millable silicone is a typical one. However, it is often difficult to develop the required flexibility as a whole. Liquid silicones are preferred. Specific examples of the addition reaction type liquid silicone include a one-component reaction type organopolysiloxane having both a vinyl group and an H-Si group in one molecule, or an organopolysiloxane having a vinyl group at a terminal or a side chain and a terminal. Alternatively, a two-part silicone with an organopolysiloxane having two or more H-Si groups in a side chain can be used. As a commercially available product of such an addition reaction type liquid silicone, there is, for example, a product name “SE-1885A / B” manufactured by Dow Corning Toray Silicone Co., Ltd.

The content of the addition reaction type liquid silicone used in the present invention is 55 to 80% by volume in the total volume, particularly 6%.
It is desirably 0 to 75% by volume. When the content of the addition-reaction type liquid silicone is less than 55% by volume, the heat radiation member for electronic parts has insufficient flexibility, and when it exceeds 80% by volume, the heat resistance becomes practically insufficient.

The addition-reaction type liquid silicone used in the present invention includes a reaction retarder such as acetyl alcohols and maleic esters, a thickener such as aerosil and silicone powder of 10 to several hundreds of μm, and a flame retardant. , Pigments and the like.

The flexibility of the heat radiating member for electronic parts of the present invention is as follows.
The density can be adjusted by the density of the crosslinked sites formed by the addition reaction type silicone and the content of the boron nitride powder, but it is particularly desirable that the compressive deformation rate when a load of 3 kg / cm ² is applied is 30% or more. Compression deformation rate is 30
If it is less than%, the mounting load when mounting and mounting on the electronic component cannot be reduced, and there is a risk that the electronic component may be damaged.

The thermal resistance in the present invention is obtained by cutting a sample (1 mm) cut into a TO-3 type into a TO-3 having a transistor.
After being set between a −3 type copper heater case (effective area 6.0 cm ² ) and a copper plate and applying a load so that 10% of the initial thickness is compressed, a power of 5 W is applied to the transistor.
, And held for 4 minutes, and is calculated from the temperature difference (° C.) between the heater case and the radiation fins by the following equation (1).

Thermal resistance (° C./W)=temperature difference (° C.) / Power (W) (1)

In the present invention, the compressive deformation rate is 10
Displacement and load display when compressing a sample of 1 mm square (1 mm thick)
Possible tester (for example, Shimadzu Corporation, product name "Auto
Graph)), using a compression speed (head moving speed) of 0.5
3kg / cm load at cm / min ^TwoChange of the sample when
It is calculated from the following formula (2) based on the ratio between the shape and the initial thickness.
Value. When the sample thickness is less than 1mm
The sample is made 1mm by simple lamination and the area is
When less than 10 mm square, total area of multiple samples
Is 100mm^TwoAnd measure the compression deformation rate.
Shall be specified.

Compressive deformation rate (%) = amount of deformation (mm) when a load of 3 kg / cm ² is applied × 100 / initial thickness of sample (mm) (2)

An example of the method of manufacturing the heat dissipating member for electronic parts of the present invention will be described. A slurry is prepared by mixing boron nitride powder with an addition-reaction liquid silicone at room temperature, and the slurry is prepared by a piston type or screw type. After extruding with an extruder to form a green sheet temporarily, laminating and heating and curing, and then cutting to a desired width (thickness) from the laminating direction, or a green sheet laminate having a desired width in the laminating direction After cutting into (thickness), the slurry prepared by vulcanization and curing, or a slurry prepared in the same manner, is poured into a mold having a concave cross section, and pressurized and heated by a press machine to temporarily form a rubber green sheet containing boron nitride powder. Then, after taking out from the mold and laminating, further heating and hardening, and then cutting to a desired width from the laminating direction. Among these, the method using an extruder is excellent in mass productivity.

The rubber green sheet containing the boron nitride powder may be formed by laminating the same material or by laminating two or more different materials. When laminating green sheets of the same material, for example, a method of laminating 50 rubber green sheets containing 35% by volume of boron nitride powder, heat-curing them, and cutting them into an arbitrary thickness perpendicular to the laminating direction. When comprising two or more different materials, for example, rubber green sheets having different boron nitride powder contents are alternately or regularly laminated, and after heating and curing, a method of cutting in the laminating direction, There is a method using different types of rubber.

The thickness of the heat dissipating member for electronic parts manufactured by the present invention is 0.2 to 10 mm, preferably 0.5 to 10 mm.
2 mm. There is no particular limitation on the surface shape,
The heat dissipating member for electronic components cut into a sheet shape can be punched and used in an arbitrary shape.

The heat radiating member for electronic parts manufactured according to the present invention can be subjected to a surface treatment as needed in order to control the adhesiveness of the surface. Specific surface treatment methods include (1) powdering boron nitride powder, (2) applying a peroxide crosslinking agent on the surface and curing only the surface,
(3) Irradiation with ultraviolet rays.

Furthermore, the heat radiating member for electronic parts manufactured by the present invention has high flexibility and slight adhesiveness, so that it is easy to handle during transportation and storage and prevents dust from adhering. For this reason, it is preferable to handle it by arranging it in a packaging material. As a packaging material, for example, polyethylene film,
A polypropylene film, a PET film, a Teflon film, a glass cloth reinforced Teflon film, or the like is used.

The heat dissipating member for electronic parts manufactured according to the present invention is used by being sandwiched between a heat-generating electronic component or a circuit board on which the heat-generating electronic components are mounted and a cooling device. It is also possible to supply it by pasting and integrating it in advance. Examples of the cooling device include a heat sink, a radiating fin, a metal or ceramic case, and the like.
1N, BN, SiC, Al ₂ O _{3 and the} like.

The electronic equipment to which the electronic component heat radiating member is used includes a computer, a CD-ROM drive, a DVD drive, a CD-R drive and the like.

[0029]

The present invention will be described more specifically with reference to examples and comparative examples.

Examples 1 to 3 Liquid A (vinyl-containing organopolysiloxane) and B
Table 1 shows the mixing ratio of the two-component addition reaction type silicone (trade name “SE-1885” manufactured by Toray Dow Corning Co., Ltd.) of the liquid (organopolysiloxane having an H—Si group) to the liquid A and the liquid B. The mixture was mixed at a mixing ratio (% by volume), and a reaction retarder containing dimethyl maleate as a main component and boron nitride powder (trade name “Dencaboron nitride GP”, manufactured by Denki Kagaku Kogyo Co., Ltd., average particle size = 7 μm) were mixed in Table 1. The mixture was mixed at room temperature at the ratio (volume%) shown in Table 1 to prepare a slurry.

This slurry was poured into the center of a mold (11 cm square) having a concave section of 1.0 mm depth, covered with a flat plate from above, and then heated under pressure at 150 ° C. for 10 minutes using a pressure press. A 1.0 mm thick rubber green sheet containing boron nitride powder was obtained.

After laminating the 50 sheets, a dryer is used at 150 ° C.
The laminate was heat-cured for × 22 hours to obtain a solidified laminate, which was cut perpendicularly to the lamination direction with a cutter to produce a heat-dissipating member (1 mm thick) for a sheet-like electronic component of the present invention.

Examples 4 to 5 Slurries having the mixing ratios shown in Table 1 were prepared in the same manner as in Example 1 and were diced into dies with slits (slit dimensions were 0.3 mm × 35 mm in Example 4; 5 was fixed in a mold having a fixed cylinder structure of 1.0 mm × 35 mm) and extruded from a slit while applying pressure with a piston to obtain a rubber green sheet containing boron nitride powder.

After laminating it to a height of 50 mm, it was cured by heating in a dryer at 150 ° C. × 22 hours to obtain a solidified laminate, which was cut vertically by a cutter in the laminating direction.
Heat dissipating member for sheet-like electronic components of the present invention (1.1 mm thickness)
Was manufactured.

Example 6 The slurry was extruded to a predetermined thickness (width 5) using a vented extruder.
(0 mm) except that a rubber green sheet containing boron nitride powder was obtained in the same manner as in Example 4 to produce a heat-dissipating member (1.1 mm thick) for a sheet-like electronic component.

Comparative Examples 1 to 3 Each of the rubber green sheets containing boron nitride powder obtained in Examples 1 to 3 was directly heated without drying in a dryer at 150 ° C. for 22 hours to form a 1.0 mm-thick rubber green sheet. A solid green sheet was produced.

COMPARATIVE EXAMPLE 4 The rubber green sheet containing the boron nitride powder obtained in Example 5 was directly laminated without drying at 150.degree.
The mixture was heated for 22 hours to produce a solidified green sheet having a thickness of 1.1 mm.

Comparative Example 5 The rubber green sheet containing the boron nitride powder obtained in Example 6 was directly laminated at 150 ° C.
The mixture was heated for 22 hours to produce a solidified green sheet having a thickness of 1.1 mm.

With respect to the heat radiating member for electronic parts and the solidified green sheet obtained above, TO-3 type and 10 mm
The sheet was cut into corners, and the thermal resistance and the compressive deformation were measured as described above. Table 1 shows the results.

[0040]

[Table 1]

Heat radiation for electronic parts manufactured in Examples 1 to 6
The member (50 mm square x 1 mm) is made of aluminum heat sink.
The heat sink was manufactured by laminating the heat sink on the flat surface of the fin. Electronic
The heat dissipating member for parts has adhesion to the aluminum plate surface
And easily adhered to the aluminum plate. The obtained chick
Heat sink attached to heat-generating electronic components 3 kg / cm ^Two
The heat-generating electronic parts were not damaged,
The heat dissipation during the operation was also very good.

[0042]

According to the present invention, a heat radiating member for electronic parts having high flexibility and excellent thermal resistance can be manufactured with low boron nitride powder content and high mass productivity.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B29K 105: 24 B29L 9:00 (72) Inventor Masato Nishikawa 1 Shinkaicho, Omuta-shi, Fukuoka Prefecture Inside the Omuta Plant of Denki Kagaku Kogyo Co., Ltd.

Claims (3)

[Claims] 1. A rubber green sheet containing boron nitride powder is formed, and a plurality of the green sheets are laminated and cured by vulcanization.
A method for producing a heat radiating member for an electronic component, comprising cutting the laminate to a desired thickness in the laminating direction, or laminating a plurality of the laminates, cutting the laminate to a desired thickness, and then vulcanizing and curing. 2. The method according to claim 1, wherein the plurality of green sheets are made of the same material. 3. The method according to claim 1, wherein the plurality of green sheets are made of different materials.