JP3531785B2 - Manufacturing method of heat dissipating member for electronic parts - Google Patents

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 dissipation member for electronic parts, which has excellent thermal conductivity and flexibility.

[0002]

2. Description of the Related Art In heat-generating electronic components such as transistors and thyristors, how to remove heat generated during use is an important issue. Conventionally, as such a heat removal method, it is generally performed to attach a heat-generating electronic component to a heat dissipation fin or a metal plate via an electrically insulating heat dissipation sheet to let the heat escape. Is a silicone rubber in which a heat conductive filler is dispersed.

In recent years, the amount of heat generated by circuits in electronic parts has become higher, and a heat radiation sheet having higher thermal conductivity than ever has been required, and damage to heat-generating electronic parts is prevented. Therefore, a strong mounting load is avoided, and in such a case, a sheet-shaped heat dissipation member having extremely low thermal resistance and high flexibility has been required.

From the viewpoint of reducing the thermal resistance of the heat dissipation sheet, a filler having a high thermal conductivity is drawing attention. In particular, boron nitride has the peculiarity that the thermal conductivity of the scale-like particles in the lengthwise direction is extremely high, and therefore, attempts have been made to use the boron nitride particles in a standing state. For example, Japanese Patent Laid-Open No. 8-
244094 discloses that boron nitride is 50% by volume or 60% by volume.
0.20 ° C / W (0.3mm
It has been shown that a sheet having a heat resistance of 0.12 ° C./W (thickness of 0.3 mm) can be obtained.
In Japanese Patent Laid-Open Publication No. 39-58, the content of boron nitride is 39% by volume or 56% by volume, and 0.41 ° C./W (0.5 mm thickness), respectively.
It is described that a thermal resistance of 0.30 ° C./W (0.5 mm thickness) can be obtained.

Further, in an attempt to randomly orient boron nitride, Japanese Patent Laid-Open No. 62-154410 discloses a sheet containing 46 to 56% by volume of boron nitride, which has a minimum thermal resistance of 0.40 ° C. / It is shown that it was possible to reduce to W (0.45 mm thickness).

[0006]

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

The object of the present invention was made in view of the above, and it is an object of the present invention to provide a method for manufacturing a heat dissipation member for electronic parts, which exhibits extremely high thermal conductivity and flexibility with a small content of boron nitride. .

[0008]

[Means for Solving the Problems] That is, according to the present invention, a rubber green sheet containing boron nitride powder is formed, a plurality of the green sheets are laminated, vulcanized and cured, and then cut to a desired thickness in the laminating direction. A method of manufacturing a heat dissipation member for an electronic component, particularly the method of manufacturing a heat dissipation member for an electronic component, wherein the plurality of green sheets are made of the same material or different materials. is there.

[0009]

The present invention will be described in more detail below.

The boron nitride powder used in the present invention can be produced by allowing a compound containing boron and a compound containing nitrogen to coexist and firing, and then pulverizing the powder. Powder X-ray analysis Graphite index (G
It is desirable that I) has a high crystallinity of 1.5 or less.

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

The content of boron nitride powder in the heat dissipation member for electronic parts of the present invention is 20 to 45% by volume, especially 25% by volume in the total volume.
It is desirable to be ˜40% by volume. If the content of the boron nitride powder is less than 20% by volume, the heat resistance as a heat dissipation member for electronic parts is insufficient, and if it exceeds 45% by volume,
Flexibility and mechanical strength are impaired.

Examples of the rubber used as the matrix in the present invention include rubber-based materials such as silicone rubber, urethane rubber, acrylic rubber, butyl rubber, ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer. Of these, silicone rubber is particularly suitable because it is excellent in flexibility, shape conformability, adhesion to heat generating surface, and heat resistance when formed into a molded body.

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

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

The addition reaction type liquid silicone used in the present invention includes reaction retarders such as acetyl alcohols and maleic acid esters, thickeners such as aerosol and silicone powder of 10 to several hundred μm, and flame retardants. It can also be used in combination with a pigment or the like.

The flexibility of the heat dissipation member for electronic parts of the present invention is
It can be adjusted by the density of the cross-linking seat formed by the addition reaction type silicone and the content of the boron nitride powder, but it is particularly preferable that the compressive deformation rate is 30% or more when a load of 3 kg / cm ² is applied. Compressive deformation rate is 30
If it is less than%, the mounting load at the time of mounting on the electronic component cannot be alleviated, and there is a risk of damaging the electronic component.

The thermal resistance in the present invention is a TO-3 type sample (1 mm) cut into a TO having a transistor built therein.
It is sandwiched between a -3 type copper heater case (effective area 6.0 cm ² ) and a copper plate, and a load is set so that 10% of the initial thickness is compressed.
Is held for 4 minutes, and is calculated from the temperature difference (° C.) between the heater case and the heat radiation fin by the following equation (1).

[0019]     Thermal resistance (° C / W) = temperature difference (° C) / power (W) ··· (1)

The compression deformation rate in the present invention is 10
Displacement and load display when compressing mm square (thickness 1 mm) sample
Possible testing machines (eg Shimadzu product name "Auto"
Graph "), compression speed (head movement speed) 0.5
Load in cm / min 3kg / cm ²Change of sample when applied
Calculated from the following equation (2) from the ratio of the shape amount and the initial thickness
Value. If the sample thickness is less than 1 mm,
By simply stacking the samples, the area is 1 mm, and the area is
When the area is less than 10 mm square, the total area of multiple samples
Is 100 mm²And measure the compressive deformation rate.
Shall be set.

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

As an example of the method for manufacturing a heat dissipation member for electronic parts of the present invention, a boron nitride powder is mixed with an addition reaction type liquid silicone at room temperature to prepare a slurry, which is prepared by a piston type or a screw type. after preliminarily molded into a green sheet extruded by an extruder, after curing laminating it heating, better to disconnect from the laminating direction to the desired width (thickness)
Method, or the slurry prepared in the same manner is poured into a mold having a concave cross-section, and the rubber green sheet containing boron nitride powder is preliminarily molded by pressurizing and heating with a press machine, then taken out from the mold and laminated. Further, after curing by heating, a method of cutting the laminate into a desired width in the laminating direction may be used. Among these, the method using the extruder is excellent in mass productivity.

The rubber green sheet containing the boron nitride powder may be laminated with the same material or two or more different materials. When stacking green sheets of the same material, for example, 50 rubber green sheets containing 35% by volume of boron nitride powder are stacked, cured by heating, and then cut into an arbitrary thickness perpendicular to the stacking direction. In the case of being composed of two or more different materials, for example, rubber green sheets having different boron nitride powder content rates are alternately or regularly laminated, and after heat curing, a method of cutting in the laminating direction, There is a method of using different kinds of rubber.

The thickness of the heat dissipating member for electronic parts produced by the present invention is 0.2 to 10 mm, preferably 0.5 to
It is 2 mm. In addition, the surface shape is not particularly limited,
The heat dissipation member for electronic parts cut into a sheet shape can be punched into an arbitrary shape for use.

The heat dissipating member for electronic parts manufactured according to the present invention may be subjected to a surface treatment as necessary in order to control the tackiness of the surface thereof. Specific surface treatment methods are (1) sprinkling boron nitride powder, (2) surface coating with a peroxide cross-linking agent, etc. to cure only the surface.
(3) For example, irradiating with ultraviolet rays.

Furthermore, since the heat dissipation member for electronic parts manufactured according to the present invention has high flexibility and slight adhesiveness, it is necessary to assist in handling during transportation and storage and to prevent dust from adhering. Therefore, it is preferable to arrange and handle the packaging material. As the packaging material, for example, polyethylene film,
Polypropylene film, PET film, Teflon film, glass cloth reinforced Teflon film, etc. are used.

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

The electronic equipment in which the heat dissipation member for electronic parts is used is a computer, a CD-ROM drive, a DVD drive, a CD-R drive or the like.

[0029]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples.

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

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

After stacking the 50 sheets, it is dried in a dryer at 150 ° C.
It was heat-cured for 22 hours to obtain a laminated solidified product, which was cut perpendicularly to the laminating direction with a cutter to manufacture the heat dissipation member (1 mm thick) for a sheet-shaped electronic component of the present invention.

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

After laminating it to a height of 50 mm, it was heated and cured at 150 ° C. for 22 hours in a dryer to obtain a laminated solidified product, which was cut vertically with a cutter in the laminating direction,
Heat dissipation member for sheet-like electronic component of the present invention (1.1 mm thick)
Was manufactured.

Example 6 A slurry having a predetermined thickness (width 5
A heat dissipation member (1.1 mm thick) for a sheet-shaped electronic component was manufactured in the same manner as in Example 4 except that a rubber green sheet containing 0 mm) of boron nitride powder was obtained.

Comparative Examples 1 to 3 Rubber green sheets containing boron nitride powder obtained in Examples 1 to 3 were heated in a drier at 150 ° C. for 22 hours without laminating to obtain 1.0 mm thick rubber green sheets. A green sheet solidified product was produced.

Comparative Example 4 The rubber green sheet containing the boron nitride powder obtained in Example 5 was dried in a dryer at 150 ° C. without being laminated.
It 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 dried in a dryer at 150 ° C. without being laminated.
It was heated for 22 hours to produce a solidified green sheet having a thickness of 1.1 mm.

Regarding the heat dissipating member for electronic parts and the green sheet solidified product obtained above, TO-3 type and 10 mm
It was cut into a corner, and the thermal resistance and the compression deformation rate were measured according to the above. The results are shown in Table 1.

[0040]

[Table 1]

Heat dissipation for electronic parts manufactured in Examples 1 to 6
Aluminum (50mm x 1mm) member made of aluminum
A heat sink was manufactured by laminating it on the flat plate surface of the tin. Electronic
The heat dissipation member for parts has adhesiveness to the aluminum plate surface
And easily adhered to the aluminum plate. Obtained hi
Attaching the sink to the heat-generating electronic components 3 kg / cm ²
Although it was pressed as, no damage was seen on the heat-generating electronic parts,
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 good mass productivity with a small content of boron nitride powder.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B29K 105: 16 B29K 105: 24 105: 24 B29L 9:00 B29L 9:00 H01L 23/36 M (56) References 8-244094 (JP, A) JP-A-55-166807 (JP, A) JP-A-56-161140 (JP, A) JP-A-57-163548 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 35/00-35/14 B32B 25/00-25/20 H01L 23/34-23/46 H05K 7/20

Claims (3)

(57) [Claims] 1. A rubber green sheet containing boron nitride powder is formed, and a plurality of the green sheets are laminated and vulcanized and cured.
A method for manufacturing a heat dissipation member for an electronic component, which comprises cutting in a desired thickness in a stacking direction. 2. The manufacturing method according to claim 1, wherein the plurality of green sheets are made of the same material. 3. The manufacturing method according to claim 1, wherein the plurality of green sheets are made of different materials.