JP2000355654A - Heat-conductive silicone molding and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a silicone molding having softness enough to absorb excessive force during fastening or compression and having a very high heat conductivity and surface pressure-sensitive adhesiveness, which molding is prepared so that it is composed of a skeleton and a resin part, there is a difference between the heat conductivity of the skeleton and that of the resin part, and it has a specified pressure-sensitive adhesive part on the surface. SOLUTION: The heat-conductive silicone molding base 1 is prepared so that it is composed of a skeleton 2 and a resin part 3 integrally formed with part or whole of the skeleton 2, there is a difference between the heat conductivity of the skeleton 2 and that of the part 3, and it has a pressure-sensitive adhesive part of at least 5 N/m on at least part of the surface. Although it is arbitrary, the difference between the heat conductivities is, say, at least 2 W/m.K. It is desirable that pressure-sensitive adhesive parts are present on the upper and lower surfaces perpendicular to the direction of the thickness of the molding and that there is a difference of at least 5 N/m between their pressure-sensitive adhesiveness. It is desirable that the coverage of the skeleton 2 or the part 3 is 50-98% in terms of a ratio by a sectional area. The molding is used as a heat-dissipating member of an electronic device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a thermally conductive silicone molding and its use.

[0002]

2. Description of the Related Art In electronic equipment, how to remove heat generated during use is an important issue. To solve this problem, heat-generating electronic components such as transistors and thyristors have been used in the past. It is attached to a heat sink such as a radiating fin or a radiating plate via a radiating member such as a sheet. As a heat conductive sheet, boron nitride (B
N) and the like in which a heat conductive filler is dispersed and contained have been widely used. Recently, a highly flexible heat radiation spacer whose flexibility has been remarkably softened to, for example, Asker C hardness of 50 or less has also been used. It is becoming.

[0003] Today, in such a heat dissipating member, further improvement in thermal conductivity is required, and this is addressed by increasing the BN filling rate.
Since the mechanical strength of the sheet is reduced, there is a limit to a method for increasing the filling rate.

BN is a scaly particle having a thermal conductivity of about 110 W / mK in a plane direction, about 2 W / mK in a direction perpendicular to the plane direction, and a thermal conductivity in the plane direction of several tens. It is known to be twice as good. Therefore, BN
By setting the plane direction of the particles to be the same as the thickness direction of the sheet, which is the direction of heat transfer, (that is, making the BN particles stand in the sheet thickness direction), it is expected that the thermal conductivity of the sheet will be dramatically improved. However, in conventional molding methods such as a calendar roll method, a doctor blade method, and an extrusion method, the orientation of BN particles occurs during sheet molding, and the plane direction of the flaky particles becomes the same as the sheet plane direction as shown in FIG. As a result, the excellent thermal conductivity in the plane direction of the BN particles was not utilized.

In order to solve such a problem, Japanese Patent Publication No.
Japanese Patent Application Publication No. -12463 proposes that BN particles are randomly oriented, but even in this case, there are still many BN particles oriented in the sheet surface direction. Cannot be said to have been raised.

[0006] Therefore, B, which is oriented in the sheet thickness direction,
Japanese Patent Publication No. 6-38460 has been proposed in order to increase the ratio of N particles to the ratio of orientation in the sheet surface direction. In this method, a silicone solid product filled with BN particles is first blocked by a molding machine, and then sliced in a vertical direction to form a sheet.
When the block size is increased, the BN particles are oriented on the side surface of the molding die, but the BN particles are randomly oriented on the inside, so that a sufficient improvement in thermal conductivity cannot be expected.

[0007] In order to sufficiently orient the BN particles to the inside, it is necessary to extrude the silicone composition containing the BN particles into a rod shape with a small cross-sectional area. By using in the extrusion direction, a heat radiating member having good heat radiation in the extrusion direction can be obtained.

In recent heat dissipating members, in addition to heat conductivity, ease of attachment to a heat dissipating fin or a heating element, and when incorporating a component to which the heat dissipating member is attached, dropping and displacement of the heat dissipating member are eliminated. Has been requested. Against this background, in the field, having surface tackiness,
In addition, the appearance of a heat dissipating member having both flexibility and high thermal conductivity has been awaited.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to provide a soft and extremely high heat capable of absorbing an excessive force during tightening or compression. An object of the present invention is to provide a thermally conductive silicone molded body having conductivity and surface adhesiveness, which is suitable as a heat dissipation member.

[0010]

That is, the present invention comprises a skeleton portion and a resin portion integrally formed with a part or all of the skeleton portion, wherein the skeleton portion and the resin portion are combined. A thermally conductive silicone molded article having different thermal conductivity and having an adhesive portion of 5 N / m or more on at least a part of its surface. Particularly, it has adhesive portions on both upper and lower surfaces perpendicular to the thickness direction of the molded product, and the difference is 5N.
/ M or more, and the ratio of the skeleton portion or the resin portion is 50 to 98% in cross-sectional area ratio.

The present invention is also a heat dissipating member for an electronic device characterized by comprising the above-mentioned heat conductive silicone molded body, and particularly has a heat resistance of 0.5 ° C./W·mm or less and an Asker C hardness of 60 ° C. It is characterized by the following.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a perspective view of a basic body of a thermally conductive silicone molded article according to the present invention, and FIG.
It is A sectional drawing. Reference numeral 1 is a basic body of a thermally conductive silicone molded body, 2 is a skeleton, 3 is a resin part, and 4 is a thermally conductive filler.

As shown in FIGS. 1 and 2, the basic body 1 of the thermally conductive silicone molding according to the present invention has a skeleton 2
And a resin part 3 integrally formed with a part or the whole of the skeleton part, and the ratio of the thermally conductive filler 4 oriented in the thickness direction of the molded article is extremely large. Moreover, the skeleton portion and the resin portion have different thermal conductivity. The present invention relates to a basic body of such a thermally conductive silicone molded article, wherein at least a part of the surface thereof has
It is characterized by having an adhesive portion of N / m or more.

The basic body of the thermally conductive silicone molded article according to the present invention itself is described in Japanese Patent Application No. 10-67159 proposed by the present applicant. Less than,
I will outline it.

As the silicone raw material used for forming the skeleton and the resin, an addition-reaction liquid silicone rubber, a thermosetting millable silicone rubber using peroxide for vulcanization, and the like are used. In the heat dissipation member of the equipment,
Since adhesion between the heat generating surface of the heat generating electronic component and the heat sink surface is required, an addition reaction type liquid silicone rubber is desirable. As a specific example, a vinyl group and an HS
One-part silicone having both i groups and two-part silicone composed of an organopolysiloxane having a vinyl group at a terminal or a side chain and an organopolysiloxane having two or more H-Si groups at a terminal or a side chain. There are silicone and the like, and as a commercial product, product name “SE-18” manufactured by Toray Dow Corning Co., Ltd.
85 "and the like. The flexibility of the cured silicone can be adjusted by the crosslink density of the silicone and the amount of the thermally conductive filler.

The thermally conductive filler used for forming the skeleton portion or the resin portion is BN powder alone or a mixed powder of BN powder and another thermally conductive filler. BN differs in thermal conductivity by several tens of times between the plane direction (a-axis) and the vertical direction (c-axis) of the flaky particles, but the present invention makes full use of the high thermal conductivity in the plane direction. be able to.

As the heat conductive filler other than BN, when insulating properties are required, silicon nitride, aluminum nitride,
Ceramic powders such as alumina and magnesia are used, and when insulating properties are not required, in addition to these ceramic powders, metal powders such as aluminum, copper, silver, and gold, silicon carbide powders, and carbon powders may be used. used. The shape of the thermally conductive filler is crushed, spherical, fibrous, acicular,
Any shape such as scaly may be used.
Those having a size of about 100 μm are used.

The thickness (c-axis direction) of the BN particles is 0.1 μm.
m or more, and less than 0.1 μm,
Particles may be destroyed when dispersed in silicone. Further, the aspect ratio (length / width ratio) of the BN particles is preferably as large as possible from the viewpoint of improving thermal conductivity,
20 or more are preferable.

Such a BN powder can be sufficiently developed, for example, by subjecting a crude BN powder to heat treatment at 2000 ° C. for 3 to 7 hours in a nitrogen atmosphere in the presence of an alkali metal or alkaline earth metal borate. After pulverization, if necessary, it can be produced by purifying with a strong acid such as nitric acid.

In the basic body of the thermally conductive silicone molded article according to the present invention, (1) the composition ratio of the skeleton portion and the resin portion, (2) the difference in thermal conductivity between the skeleton portion and the resin portion,
(3) The ratio of the resin portion formed inside one hollow portion,
(4) Regarding the cross-sectional shape of the skeleton or resin part,
There is no particular limitation. Hereinafter, these will be described in more detail.

The composition ratio (%) of the skeleton portion or the resin portion is represented by an area ratio occupied by the skeleton portion or the resin portion in the cross-sectional area (= cross-sectional area of each bone or resin portion / total cross-sectional area × 100). 50
Preferably it is ~ 98%.

Whether to increase the thermal conductivity of the skeleton or the resin is determined according to the purpose of use. The difference in thermal conductivity between the two is also arbitrary, but one example is 2.
W / m · K or more.

As a method for providing a difference in thermal conductivity between the skeleton portion and the resin portion, it is possible to carry out the method based on the filling amount of the BN powder, the orientation of the BN powder, or both. When the BN powder is used according to the filling amount, it can be easily performed by using silicone compositions having different BN contents.
In this case, the content of the thermally conductive filler in the main part of heat transfer (skeleton part or resin part) is 35 to 60% by volume, particularly 4%.
It is preferable to set it to 0 to 55% by volume. If it is less than 35% by volume, sufficient thermal conductivity cannot be imparted to the silicone molded body, and if it exceeds 60% by volume, the mechanical strength decreases. The reason why the thermal conductivity of the skeleton portion is different from that of the resin portion as in the present invention is that high thermal conductivity is borne by a portion having high thermal conductivity, and high flexibility is borne by a low portion.

The resin portion formed inside the hollow portion of the skeleton portion will be described. In the case where the skeleton portion is a main portion of heat transfer, the more flexible the resin portion, the more the skeleton portion generated during tightening or compression. Deformation can be absorbed, and the adhesion to the surface of the heating element increases, so that good thermal conductivity can be obtained. The hardness difference between the skeleton portion and the resin portion is not limited, but is preferably 5 or more in Asker C hardness. In addition, there is no problem even if the resin portion is partially in a void state, and such a structure may be advantageous depending on the application. The method of providing a difference in hardness between the skeleton portion and the resin portion can be performed depending on the amount of filler, the type of silicone, the crosslink density, and the like.

The cross-sectional shape of the skeleton portion or the resin portion is triangular,
Polygons such as a square, a hexagon, a lattice, a rhombus, and a trapezoid, a circle, an ellipse, a waveform, a concentric circle, a radial shape, and a spiral shape are possible.

A major feature of the present invention is that an adhesive portion of 5 N / m or more is provided on at least a part of the surface of the heat-conductive silicone molded body. In particular, it is preferable that the adhesive portions are formed on both upper and lower surfaces perpendicular to the thickness direction of the molded body, and the difference is preferably 5 N / m or more.

As the method of forming the adhesive portion, (1) the adhesive portion is provided by adjusting the type of one or both of the skeleton portion and the resin portion and the crosslinking density thereof, and (2)
For example, an adhesive may be applied to the surface of the thermally conductive silicone molded article. Examples of the pressure-sensitive adhesive used in the latter include an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a thermally conductive grease, and a low-crosslinking density silicone composition containing or not containing a thermally conductive filler. Such an adhesive can also be blended in the raw material for forming the resin part.

The application of the pressure-sensitive adhesive can be performed by screen printing, a roll coater or the like. When the adhesive portion is formed in a limited portion or when the adhesive portion is formed in a complicated shape, it is more effective to use screen printing.

The thicker the adhesive portion, the higher the adhesive strength, but the higher the thermal resistance. Therefore, the thickness is preferably about 10 to 100 μm, particularly preferably 10 to 50 μm.

On the other hand, in the former method of forming an adhesive portion by adjusting the type of silicone and the crosslinking density thereof, the portion where the adhesive portion is not formed has a wavelength of 100 to 280.
Irradiation with an electromagnetic wave of nm (ultraviolet light in the UV-C region) can be suitably performed.

The degree of adhesiveness of the adhesive portion is such that the heat radiating member is not dropped or displaced when the heat radiating member is attached to the heat generating element, and the heat radiating member is cooled by a heat radiating fin or a housing with the heat radiating member interposed therebetween. In the electronic parts, considering that it is preferable that the heat radiating member is adhered to either the heat generating member or the heat radiating fin at the time of inspection or repair,
5 N / m or more is required. The upper limit is not particularly limited, and may be any size as long as it can be detached.

The shape of the thermally conductive silicone molded article of the present invention is not limited, and an appropriate shape is selected according to the application. The sheet or rectangular member is used as a heat dissipating member of an electronic device such as a heat conductive sheet or a highly flexible heat dissipating spacer.

The heat dissipating member of the present invention is constituted by the heat conductive silicone molding of the present invention, and has a heat resistance of 0.5 ° C./W·mm or less and an Asker C hardness of 60 or less. Is preferred. When a BN powder alone or a mixed powder of a BN powder and another heat conductive filler is used as the heat conductive filler, X in the thickness direction of the heat radiating member.
In the X-ray diffraction diagram obtained by irradiating X-rays, <100>
The peak ratio (<002> / <100>) of the <002> plane (c-axis) to the plane (a-axis) is preferably 1 or less.

[0034]

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

Example 1 In order to form the skeleton, the volume ratio of the liquid A (organopolysiloxane having a vinyl group) to the liquid B (organopolysiloxane having an H-Si group) was changed to liquid A: liquid B = 1: 1. A two-component addition reaction type liquid silicone obtained by mixing at a ratio of 1 (trade name “SE-188” manufactured by Toray Dow Corning Co., Ltd.)
5 ") 45% by volume and 55% by volume of BN powder (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name" Dencaboron Nitride ") having an average particle diameter of 15 μm and an average particle thickness of 1 μm were mixed with a commercially available mixer to conduct heat conduction. A sex compound was prepared.

This compound was extruded from a die having 20 holes each having a diameter of 3 mm and formed into an uncured rod-shaped silicone molding, cut into a length of 6 cm, and placed in a prepared resin outer frame. Stacked into an aggregate. This aggregate is composed of an uncured skeleton portion and a hollow portion serving as a resin portion, and has a planar shape of 60 × 60 m.
m.

Next, in order to form an adhesive resin portion, a liquid addition reaction type liquid silicone was mixed with liquid A: liquid B = 1.
The mixture was mixed at a volume ratio of 2: 1 and adjusted so as to exhibit an adhesive force. This was poured into a mold filled with a rod-shaped silicone molded product, treated in a vacuum for 10 minutes, and then vulcanized and cured with a hot air drier at 120 ° C. for 5 hours. After that, thickness 1m
m to prepare a thermally conductive silicone molded article of the present invention.

Example 2 In order to make the skeleton part sticky, the mixing ratio of the two-component addition reaction type liquid silicone used for forming the skeleton part was as follows:
Example 1 except that the volume ratio of solution B was 1.2: 1.
A thermally conductive silicone molded body was produced in the same manner as in the above.

Example 3 As the slurry used for forming the resin part, the volume ratio of the two-component addition-reaction type liquid silicone was set at A: B = 1: 1.
1 according to Example 1 except that a mixture of 80% by volume of silica powder and 20% by volume of silica powder was used.
And a silicone-based pressure-sensitive adhesive (trade name “PSA, manufactured by Toshiba Silicone Co., Ltd.”) is formed on the entire upper surface perpendicular to the thickness direction.
6574 ”) was applied to a thickness of 10 to 20 μm to prepare a thermally conductive silicone molded article of the present invention.

Example 4 In place of the silicone-based pressure-sensitive adhesive, 70% by volume of the two-component addition reaction type liquid silicone in which the volume ratio of the liquid A: liquid B = 1.2: 1 and 30 volumes of silicon nitride powder were used. %, Using a slurry obtained by mixing the resulting slurry with a thickness of 50 μm by screen printing, followed by curing with a hot air dryer at 120 ° C., in the same manner as in Example 3.
A heat conductive silicone molding was produced.

Example 5 A commercially available heat conductive grease (trade name "G-747", manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of the silicone-based pressure-sensitive adhesive, and was applied to a thickness of 50 μm by screen printing. In the same manner as in Example 3, a thermally conductive silicone molded body was produced.

Example 6 The slurry prepared in Example 4 was applied to one side of the thermally conductive silicone molded article of the present invention prepared in Example 1 by screen printing to a thickness of 50 μm and cured to obtain a heat conductive material. A silicone molding was prepared.

Comparative Example 1 The thermally conductive compound prepared in Example 1 was extruded using a die having a flat extrusion port, and an uncured silicone molded article having a planar shape was extruded and cured. In the same manner as in Example 1, a thermally conductive silicone molded body was produced.

Comparative Example 2 A basic heat-conductive silicone molded body was formed in the same manner as in Example 3 except that the silicone-based pressure-sensitive adhesive was not applied, and was used as a heat-conductive silicone molded body. .

With respect to the thermally conductive silicone molded body obtained above, the composition ratio of the resin part, adhesive strength, thermal resistance in the thickness direction, and Asker-C hardness were measured as follows. In addition, the attachment property to the aluminum radiation fin was also evaluated. Table 1 shows the results.

(1) Composition Ratio of Resin Portion The occupied area ratio of the resin portion per sectional area of the thermally conductive silicone molded article was measured with a microscope.

(2) Adhesive Strength A heat-conductive silicone molded product having a size of 125 mm × 25 mm × 1 mm was placed on a 200 mm × 40 mm SUS plate.
A roller with a load of 0 g is reciprocated once at a speed of about 300 mm / min to perform pressure bonding. Thereafter, 90 ° peel strength was measured at a tensile speed of 50 mm / min using a tensile tester.

(3) Thermal Resistance A thermally conductive silicone molded article having a thickness of 1 mm is cut into a TO-3 shape, which is sandwiched between a TO-3 type copper heater case and a copper plate, and a tightening torque of 5 kgf-cm. After setting at, a power of 15 W was applied to the copper heater case, and the temperature was maintained for 4 minutes. The temperature difference between the copper heater case and the copper plate was measured, and the equation, thermal resistance (° C./W·mm)=｛temperature difference (° C.) )
/ Power (W)} / sheet thickness (mm).

(4) Asker C hardness A 1 mm thick thermally conductive silicone molded article was cut into a circular shape (diameter 29 mm), and ten pieces were stacked to form a 10 mm thick test piece. (Manufactured by Kobunshi Keiki Co., Ltd.)
By applying a measurement load of 500 g, the hardness was measured.

(5) Attaching property to aluminum radiating fins Commercially available aluminum radiating fins have a size of 30 mm × 30 m.
After adhering the thermally conductive silicone molded article of mx 1 mm, it was reciprocated 10 times in the lateral direction to confirm the presence / absence of positional deviation. In addition, the radiation fins were turned upside down to check for a drop.

[0051]

[Table 1]

From Table 1, it can be seen that the thermally conductive silicone molded articles of Examples 1 to 6 have significantly improved thermal conductivity as compared with Comparative Example 1, and have a higher surface conductivity than Comparative Examples 1 and 2. It can be seen that the adhesive portion is excellent in the attachment property because the adhesive portion is formed on the adhesive.

Next, the heat conductive silicone molded body produced in the example was used as a heat radiating member, and was attached to the heat sink side.
When it was attached to a heating element such as a ball-grid array type SRAM, it could be assembled without dropping or misalignment. In addition, even during operation, temperature rise can be suppressed low, and a highly reliable electronic device can be manufactured.

[0054]

According to the present invention, it is possible to provide a silicone molded body having adhesiveness suitable for a heat radiation member, and having high flexibility and high thermal conductivity. The heat-conductive silicone molded article of the present invention is suitable as a heat-radiating member for electronic devices such as a heat-conductive sheet and a flexible heat-radiating spacer.

[Brief description of the drawings]

FIG. 1 is a perspective view of a basic body of a thermally conductive silicone molding according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a cross-sectional view of a conventional heat conductive sheet in a thickness direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Basic body of a heat conductive silicone molded object 2 Skeleton part 3 Resin part 4 Heat conductive filler

Claims (5)

[Claims] 1. A skeleton part and a resin part formed integrally with a part or all of the skeleton part, wherein the skeleton part and the resin part have different thermal conductivity, and furthermore, A thermally conductive silicone molded product, characterized in that at least a part of the surface has an adhesive portion of 5 N / m or more. 2. The thermally conductive silicone molded product according to claim 1, wherein the molded product has adhesive portions on both upper and lower surfaces perpendicular to the thickness direction, and the difference is 5 N / m or more. . 3. The ratio of the skeleton portion or the resin portion is 5 in cross-sectional area ratio.
The thermally conductive silicone molded product according to claim 2, wherein the content is 0 to 98%. 4. A heat dissipating member for an electronic device, comprising the heat conductive silicone molded product according to claim 1, 2 or 3. 5. The heat resistance is 0.5 ° C./W·mm or less and Asker C hardness is 60 or less.
A heat dissipating member according to any one of the preceding claims.