JP2000108220A - Thermally conductive resin molding, its manufacture and use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a highly flexible and highly thermally conductive heat dissipation member with good productivity by forming the member out of a resin molding which contains a thermally conductive filler and is easily deformed by an external force and forming it in a structure having communicating holes. SOLUTION: The thermally conductive resin molding 1 is a molding containing thermally conductive filler 3 in a resin 2 or a resin molding to be easily deformed by an external force and containing communicating holes 4. The filler 3 contains BN particles. The resin 2 is a silicon. A shape of the molding is sheet-like. The holes 4 are formed in a thickness direction of the sheet with a porosity of a range 5 to 50%. Further, a ratio of the particles oriented in the thickness direction of the sheet is increased more than that of the particles oriented in a width direction of the sheet. Such the molding 1 is obtained by molding an uncured bar-like mold by using a resin composition containing the filler 3, providing air gaps to become a plurality of the holes 4, and accumulated. Thereafter, it is cut and cured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermally conductive resin molded article, its production method and use. More specifically, the present invention relates to a heat conductive molded body suitable as a heat radiating member to be interposed between a heat generating electronic component and a heat sink when radiating heat of an electronic device, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In electronic equipment, how to remove heat generated during use has become an important issue. Conventionally, heat-generating electronic components such as transistors and thyristors have been used.
It is performed by attaching to a heat sink such as a heat radiation fin or a heat radiation plate via a heat conductive sheet. The heat conductive sheet is made of a resin in which a heat conductive filler is dispersed and contained, and is widely used for mounting heat-generating electronic components because of its good heat conductivity. Further, recently, a highly flexible heat-radiating spacer in which the flexibility of the heat conductive sheet is significantly increased to, for example, 50 or less in Asuka C hardness has been used.

In order to improve the thermal conductivity of the thermally conductive sheet, it is sufficient to increase the filling rate of a thermally conductive filler such as boron nitride (BN). However, since the mechanical strength of the sheet is reduced, a high filling rate is required. Had a limit.

BN is a scale-like particle, and the thermal conductivity of the particle itself is about 110 W / mK in a scale-like surface direction.
In contrast, about 2 W /
It is known that the thermal conductivity of BN particles is only about mK, and the thermal conductivity of the BN particles is several tens times better in the plane direction. That is, by setting the surface direction, which is the direction in which the thermal conductivity of the BN particles is excellent, to be the same as the thickness direction of the sheet through which the heat dissipation sheet transfers heat (the BN particles are set up in the sheet thickness direction), the thermal conductivity is dramatically increased. However, in the conventional production methods (calender roll method, doctor blade method, extrusion method), the orientation of the BN particles occurs at the time of sheet molding, and as shown in FIG. Was the same as the sheet surface direction, and the excellent thermal conductivity in the surface direction of the BN particles was not utilized.

In order to solve such problems, Japanese Patent Publication No. Hei 6-12643 proposes randomly aligning BN particles. However, there are still many laterally oriented BN particles. Therefore, it cannot be said that the excellent thermal conductivity in the plane direction of the BN particles is sufficiently utilized.

Therefore, as shown in FIG. 2, a method of improving the thermal conductivity by increasing the ratio of the BN particles oriented in the sheet thickness direction to the ratio of the BN particles oriented in the sheet width direction is as follows. Japanese Patent Publication No. Hei 6-38460 discloses that, in this method, a silicone solidified product filled with BN particles is blocked by a molding machine and then sliced in a vertical direction to form a sheet. The cross-sectional area is too wide and the degree of orientation of BN inside is insufficient, and a sufficient improvement in thermal conductivity cannot be expected.

Further, in any of the methods, when the BN particles are highly filled in order to improve the thermal conductivity, the sheet becomes hard, and when the heat-generating electronic component is weak against the load, the sheet is damaged by the tightening force at the time of mounting. There was a problem.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has as its object to dispose a heat radiating member such as a heat conductive sheet between a heat generating electronic component and a heat sink.
To provide a heat-radiating member having high flexibility and high thermal conductivity capable of absorbing excess tightening force by a communication hole formed in a heat-dissipating member when interposed by a tightening force, thereby reducing damage to a heat-generating electronic component. It is. Further, another object of the present invention is to further provide, as shown in FIG. 2, that more thermally conductive filler particles oriented in a nearly upright state are present in the thickness direction than in the width direction of the heat dissipation member. An object of the present invention is to provide a heat dissipating member having high thermal conductivity.
Another object of the present invention is to manufacture the above-mentioned heat-radiating member having high flexibility and high thermal conductivity with high productivity.

[0009]

That is, the present invention provides the following. (Claim 1) A thermally conductive resin molded article comprising a resin molded article containing a thermally conductive filler, which is easily deformed by an external force, and having a communication hole. (2) The thermally conductive resin molded article according to (1), wherein the thermally conductive filler contains BN particles and the resin is silicone. (3) The thermal conductivity according to (1) or (2), wherein the shape of the molded body is a sheet, the communication holes are formed in the thickness direction of the sheet, and the porosity is 5 to 50%. Resin molding. (4) The thermally conductive resin molded article according to (3), wherein the proportion of BN particles oriented in the sheet thickness direction is higher than the proportion of BN particles oriented in the sheet width direction. (5) A heat dissipating member for an electronic device, comprising the thermally conductive resin molded product according to (3) or (4). (6) An electronic device, wherein the heat radiating member according to (5) is interposed between a heat-generating electronic component of the electronic device and a heat sink in a state where the communication hole is crushed. (Claim 7) An uncured rod-shaped molded product is formed by using a resin composition containing a thermally conductive filler, and a plurality of these are aggregated by providing a void serving as a communication hole, and the aggregate is formed to a desired length. A method for producing a thermally conductive resin molded article, comprising cutting into pieces and then curing, or cutting after curing. (Claim 8) The resin composition containing a thermally conductive filler is a silicone containing 20 to 70% by volume of BN particles, the cross-sectional area of the rod-shaped molded product is 0.5 to 300 mm ² , and the porosity of the aggregate is 5 to 5. The method for producing a thermally conductive resin molded article according to claim 7, wherein the cut width is 50% and the cut width is 0.05 to 5 mm.

[0010]

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

The resin in the present invention includes silicone rubber (liquid silicone rubber vulcanized by addition reaction, heat-curable millable silicone rubber using peroxide for vulcanization), epoxy resin, olefin resin and the like. Is a resin generally used for electronic materials.

In a heat radiation member of an electronic device, it is required that the heat generating surface of the heat generating electronic component be in close contact with the heat sink surface.
A resin having flexibility or a resin having rubber elasticity is desirable. As the flexible resin, a solidified addition reaction type liquid silicone is preferable. Specific examples thereof include a one-part silicone having both a vinyl group and an H-Si group in one molecule, and a terminal or side silicone. There are two-component silicones of an organopolysiloxane having a vinyl group in the chain and an organopolysiloxane having two or more H-Si groups in a terminal or a side chain. As a commercially available product of such an addition reaction type liquid silicone, "SE-1" manufactured by Toray Dow Corning Co., Ltd.
885 "or the like. The flexibility of the resin
It can be adjusted by the cross-link density of silicone or the filling amount of the heat conductive filler.

The heat conductive filler used in the present invention may be boron nitride, silicon nitride,
Ceramic powders such as aluminum nitride, alumina, and magnesia are used.
In addition to the above ceramic powders, aluminum, copper, silver,
Metal powder such as gold, silicon carbide powder, carbon powder and the like are used. One or two or more of these heat conductive fillers are used. The shape of the heat conductive filler may be any shape such as a crushed irregular shape, a spherical shape, a fibrous shape, a needle shape, and a scale shape, and the average particle size is about 1 to 100 μm.

[0014] Even in the case of the above-mentioned heat conductive filler, BN powder may be used alone or in combination with other heat conductive fillers in a heat dissipating member of an electronic device such as a heat conductive sheet or a highly flexible heat dissipating spacer. desirable. Because BN
As described above, the heat conductivity in the direction of the hexagonal annular mesh plane (a-axis) differs from that in the direction perpendicular to the hexagonal annular mesh plane (c-axis) by about several tens of times. This is because high thermal conductivity in the direction can be 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 resin. The aspect ratio (length / width ratio) of the BN particles is preferably as large as possible from the viewpoint of improving thermal conductivity, and the aspect ratio is preferably 20 or more.

Such BN powder is obtained, 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 to develop crystals. After pulverization, and if necessary, purification with a strong acid such as nitric acid.

The thermally conductive resin molded article of the present invention is a molded article in which the resin contains the thermally conductive filler.
It is characterized by being easily deformed by an external force and having a communication hole. The content of the heat conductive filler is 20
It is preferably from 70 to 70% by volume, particularly preferably from 35 to 45% by volume. If the amount is less than 20% by volume, sufficient thermal conductivity cannot be imparted to the resin molded body, and if it exceeds 70% by volume,
The mechanical strength of the resin molded article is reduced, and the application is significantly restricted.

In the present invention, "easy to be deformed by an external force" means that it has high flexibility to be deformed to the extent that it can be seen from the appearance even with a small load of about 0.1 MPa. It is preferable that the degree of deformation is 5% or more when a load of 0.1 MPa is applied, or the Asker C hardness is 100 or less. The adjustment can be performed by the degree of curing of the resin, the filling amount of the heat conductive filler, and the size and number of the communication holes described later.

The "communication hole" in the present invention means a pore penetrating from one surface to the opposite surface of the resin molded body as illustrated in FIG. As the size of the communication hole, the average of the pore cross-sectional area is preferably 0.1 to 10 mm ² , and the number thereof may be one or more, but the porosity of the resin molded product is particularly preferably 5 to 50%. 10-30
%.

The communicating hole can be confirmed visually or by microscopic observation, and the pore cross-sectional area can be measured by image processing of a micrograph. Further, the porosity of the resin molded body can be determined by measuring the ratio of the pore sectional area per unit sectional area of the resin molded body.

The shape of the thermally conductive resin molded article of the present invention is completely arbitrary, and an appropriate shape is selected according to the application. The sheet or rectangular one is used as a heat conductive sheet or a highly flexible heat radiation spacer. In this case, the communication hole is preferably formed in the thickness direction of the resin molded body. Furthermore, as shown in FIG. 2, it is more preferable that the ratio of the BN particles oriented in the thickness direction of the sheet is higher than the ratio of the BN particles oriented in the width direction of the sheet. Specifically, in the X-ray diffraction diagram obtained by irradiating X-rays in the thickness direction of the sheet, the <100> plane (a
Ratio of the <002> plane (c-axis) to the (002 axis)
2> / <100>) is preferably 6 or less. A method of filling the resin with the BN particles in such a state will be described later.

The thermally conductive resin molded article of the present invention is suitable as a heat dissipating member for electronic equipment. The open pore surfaces of the communication holes are brought into contact with the heat-generating electronic component surface and the heat sink surface, and are interposed therebetween. It is preferably used. Normally, a fastening external force is applied to the interposition of the heat radiating member, so that a part or the whole of the communication hole is crushed.

Next, a method for producing the thermally conductive resin molded article of the present invention will be described.

First, a resin and a heat conductive filler are mixed. The ratio of both is preferably 30 to 80% by volume of the resin and 70 to 20% by volume of the heat conductive filler. Mixing is performed using a roll mill, a kneader, a Banbury mixer, or the like. Next, the mixture is extruded from a die having a plurality of holes to form an uncured rod-shaped molded product, and a plurality of these are aggregated by providing a void serving as a communication hole. The cross-sectional area (corresponding to the hole diameter of the die) of one rod-shaped molded product is 0.1 mm.
The thickness is preferably 5 to 300 mm ^{2. When} the heat conductive filler is BN powder, the BN particles can be oriented in a certain direction when the mixture passes through a narrow flow path of the die. The ratio of the BN particles oriented in the thickness direction of the thermally conductive resin molded article of the present invention can be easily increased more than the ratio of the BN particles oriented in the width direction.

Next, a plurality of uncured rod-shaped moldings are gathered together by providing voids serving as communication holes of the thermally conductive resin molded article of the present invention, and cut into a desired length and then cured. Alternatively, it is possible to produce the thermally conductive resin molded article of the present invention by cutting it to a desired length after curing.

The aggregate shape of the uncured rod-shaped molded product is a columnar body, and its planar (cross-sectional) shape is a rectangle, ellipse, circle, or the like having a communication hole. Regarding the size of the planar shape, it is preferable that the maximum length such as a diagonal line, a diameter, and a major axis is about 30 cm from the viewpoint of easy cutting and curing of the resin.

Curing of the aggregate of the uncured rod-shaped moldings is carried out by passing them through a far-infrared drying oven and heating them in a hot-air dryer. The cutting width of the rod-shaped molded product, that is, the thickness of the thermally conductive resin molded product of the present invention is 0.05 to
It is preferably 5 mm, especially 0.2 to 2 mm.

[0028]

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

Example 1 A BN powder having an average particle diameter of 15 μm and an average particle thickness of 1 μm (trade name “DENCABORON NITRIDE” manufactured by Denki Kagaku Kogyo Co., Ltd.) )) In the proportions shown in Table 1, mixed with a mixer ("BB mixer" manufactured by Kobe Steel), and further vulcanizing agent for silicone rubber (2,4-dichloroperoxide) and flame retardant for silicone rubber. A small amount of an agent (platinum-containing isopropyl alcohol) and a small amount of a filler dispersant (trade name “A-173” manufactured by Nippon Unicar Co., Ltd.) were added to prepare a thermally conductive compound.

Next, the above compound was extruded from a die having 17 mm rows and 17 mm rows of holes having a diameter of 3 mm to form an uncured rod-shaped product, and all of them were assembled by their own weight and side rolls. While passing through a far-infrared drying oven at 150 ° C. for 5 minutes for vulcanization and curing (the planar shape of the aggregate is about 50 × 50 mm), the assembly was cut to a width (thickness) of 1 mm. The thermally conductive resin molded article of the present invention as shown in the following was produced.

Example 2 A two-component addition reaction type liquid silicone (manufactured by Dow Corning Toray Co., Ltd.) comprising a liquid A (organopolysiloxane having a vinyl group) and a liquid B (organopolysiloxane having an H-Si group) as resins. Thermal conductive resin molding was carried out in the same manner as in Example 1 except that a compound was prepared by mixing the liquid A to the liquid B with the mixing ratio (volume%) shown in Table 1 with the trade name “SE-1885”). Body manufactured.

Example 3 A thermally conductive resin molded article was produced in the same manner as in Example 2 except that the composition was not passed through a far-infrared dryer.

Comparative Examples 1 and 2 A resin molded body was produced in the same manner as in Example 1 or Example 2, except that a die having a flat extrusion port was used.

Comparative Example 3 The thermally conductive compound prepared in Example 1 was subjected to a pressure of 5
Pressing was performed at 0 kg / cm ^{2 at} a temperature of 150 ° C. for 30 minutes to produce a resin molded body.

The resin molded body obtained above was measured for thermal conductivity, hardness as an index for “easy deformation by external force”, presence / absence of communication holes, and porosity as described below.
Table 1 shows the results.

(1) Thermal Conductivity The resin molded body was cut into 25 × 25 mm, and cut into 15 × 1
After sandwiching between a 5 mm copper heater case and a copper plate and setting with a tightening torque of 5 kgf-cm, 15 W of power is applied to the copper heater case and held for 4 minutes, and the temperature difference between the copper heater case and the copper plate is measured. , Thermal resistance (℃ /
W) = temperature difference (° C.) / Power (W), and the thermal resistance was calculated. Next, using a copper heater case and a copper plate with a heat transfer area of 2.25 cm ² , the thermal conductivity was calculated by the following equation.

Thermal conductivity (W / mK) = ｛power (W) ××
Heat thickness (mm)｝ / ｛heat transfer area (m ^Two) X temperature difference
(℃)｝

(2) Hardness as an index of “Easily deformed by external force” Hardness A number of resin moldings are stacked and the thickness is 10 mm.
The hardness was measured with a hardness meter.

(3) Presence or absence of communication hole The observation was performed visually and by a micrograph.

(4) Porosity The ratio of the pore area per unit sectional area of the resin molded article was measured.

[0041]

[Table 1]

From Table 1, it can be seen that the thermally conductive resin molded product of the example has significantly improved thermal conductivity and high flexibility compared to the resin molded product of the comparative example.

Next, the thermally conductive resin molded article of the present invention manufactured in the example was interposed by applying a slight load between the ball-grid array type SRAM and the heat sink, and was brought into close contact. A highly reliable electronic device with a small temperature rise at the time was manufactured.

[0044]

According to the present invention, a resin molded body having high flexibility and high thermal conductivity is provided. The heat conductive resin 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. Further, according to the method for producing a thermally conductive resin molded article of the present invention, a highly flexible and highly thermally conductive resin molded article can be produced with high productivity.

[Brief description of the drawings]

FIG. 1 is a perspective view of a thermally conductive resin molded article of 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 Thermal conductive resin molded object 2 Resin 3 Thermal conductive filler 4 Communication hole

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 7/20 H01L 23/36 MF Term (Reference) 4F213 AA33 AA45 AB05 AB10 AD04 AE03 AE10 AH33 WA06 WA15 WA43 WA53 WA83 WA87 WB01 5E322 AA11 AB04 AB11 FA05 5F036 AA01 BB21 BD14 BD21

Claims (8)

[Claims] 1. A thermally conductive resin molded product comprising a thermally conductive filler-containing resin molded product which is easily deformed by an external force and having communication holes. 2. The thermally conductive resin molded product according to claim 1, wherein the thermally conductive filler contains BN particles, and the resin is silicone. 3. The thermal conductivity according to claim 1, wherein the shape of the molded body is a sheet, the communicating holes are formed in the thickness direction of the sheet, and the porosity is 5 to 50%. Resin molding. 4. The thermally conductive resin molded article according to claim 3, wherein the proportion of the BN particles oriented in the sheet thickness direction is higher than the proportion of the BN particles oriented in the sheet width direction. 5. A heat-dissipating member for an electronic device, comprising the heat-conductive resin molded product according to claim 3. 6. An electronic device, wherein the heat radiating member according to claim 5 is interposed between a heat-generating electronic component of the electronic device and a heat sink in a state where the communication hole is crushed. 7. An uncured rod-shaped molded product is formed by using a resin composition containing a thermally conductive filler, and a plurality of these are aggregated by providing a void serving as a communication hole, and the aggregated material is formed into a desired length. A method for producing a thermally conductive resin molded article, comprising cutting into pieces and then curing, or cutting after curing. 8. The resin composition containing a thermally conductive filler, wherein the resin composition comprises BN.
It is a silicone containing 20 to 70% by volume of particles, the cross-sectional area of the rod-shaped molded product is 0.5 to 300 mm ² , the porosity of the aggregate is 5 to 50%, and the cutting width is 0.05 to 5 mm. The method for producing a thermally conductive resin molded article according to claim 7, characterized in that: