JP2001217360A - Flexible heat-radiation spacer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-radiation spacer with both high handling and repairing characteristics, with no degradation in flexibility and heat conductivity. SOLUTION: The flexible heat-radiation spacer comprises a silicon-solidified material filled with a heat-conductive filler. At least one surface comprises a rough part, and the total occupation area of the rough part is 50-90% of the area of a surface comprising the rough part. With a load of 98 KPa applied, the compression rate of a surface layer which is defined as a part between a surface and a 20% of the entire thickness is 1-5% of the entire thickness while a difference from the entire compression rate is less than 20%. The entire compression rate is especially preferred to be 10% or above while a heat conductivity to be 1 W/m.K or above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible heat radiation spacer which is suitable for heat radiation of a heat-generating electronic component and has improved handleability and repairability.

[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 the heat conductive sheet, a resin in which a heat conductive filler such as boron nitride or aluminum oxide is dispersed and contained is widely used.

In recent years, as electronic devices have become smaller and more highly packaged, there is no space for mounting radiating fins and the like, or when electronic devices are hermetically sealed and it is difficult to radiate heat from the radiating fins, heat is generated. A method has been adopted in which heat generated from a conductive electronic component is directly radiated to a case or the like of an electronic device. In this case, a heat radiation spacer having a thickness sufficient to fill a space between the heat-generating electronic component and the case is used.

[0004] In such a heat radiation spacer, an extremely soft heat radiation spacer having a thickness compression ratio of 30% or more when a load of 98 KPa is applied, for example, so as not to damage the heat-generating electronic parts due to the pressing pressure during mounting. It is used. This heat radiation spacer is rich in flexibility, but is poor in handleability. Therefore, to improve the heat radiation spacer, a spacer with a reinforcing layer has been conventionally proposed. For example, a laminate in which a flexible layer is laminated on a reinforcing layer formed in advance (Japanese Patent Application Laid-Open Nos. 2-196453 and 6-1555)
No. 17). However, these heat radiation spacers are easy to handle, but the manufacturing process is complicated, and the hardness of the flexible layer and the reinforcing layer is extremely different,
There is a problem that flexibility is greatly reduced, adhesion to the surface is also deteriorated, and thermal conductivity is reduced.

[0005] Therefore, today's demands are that, in addition to thermal conductivity and flexibility, positioning and temporary fixing during the work of attaching the heat radiating spacer are easy (handlability), and replacement and product replacement due to sticking failure are required. It is easy to remove for repair (repairability). Since the conventional heat radiation spacer has a flat surface, it is difficult to peel off the heat-generating electronic component when the surface of the heat-generating electronic component is flat, and there is a problem in repairability.

[0006]

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 heat radiation spacer having improved handleability and repairability without impairing flexibility and thermal conductivity. It is to provide.

[0007]

That is, the present invention comprises a cured silicone material filled with a thermally conductive filler, at least one surface of which has an uneven portion. The total occupied area ratio is 50 to 90% with respect to the surface area of the surface having the irregularities, and 98K
When a load of Pa is applied, the compressibility of the surface layer defined as a portion from the surface to 20% of the total thickness is 1 to 1 of the total thickness.
A flexible heat-radiating spacer characterized by being 5% and having a difference from the overall compression ratio of 20% or less. In particular, the overall compressibility is 10% or more, and the thermal conductivity is 1 W / m ·
It is preferably at least K.

[0008]

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

First, the flexible heat radiation spacer of the present invention comprises:
It is composed of a cured silicone material filled with a thermally conductive filler.

As the silicone material, an addition-reaction liquid silicone rubber, a heat-curable millable silicone rubber using a peroxide for vulcanization, and the like are used. Since the adhesiveness between the heat-generating surface and the heat-sink surface is required, a highly flexible addition-reaction liquid silicone rubber is desirable. Specific examples thereof include a one-part silicone 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 two or more at the terminal or a side chain. There is a two-part silicone with an organopolysiloxane having an H-Si group, and commercially available products include "SE-1885" (trade name, manufactured by Toray Dow Corning Incorporated).
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 ratio of the silicone rubber to the thermally conductive filler is 30 to 80% by volume, especially 40 to 7% by volume.
It is preferable that the content of the heat conductive filler is 0 to 20% by volume, particularly 60 to 30% by volume. If the silicone rubber content is less than 30% by volume or the thermally conductive filler exceeds 70% by volume, the flexibility becomes insufficient. Further, when the silicone rubber exceeds 80% by volume or the heat conductive filler is less than 20% by volume, the thermal conductivity is reduced.

As the heat conductive filler, when insulation is required, one or more of ceramic powders such as boron nitride, silicon nitride, aluminum nitride, aluminum oxide, magnesium oxide, zinc oxide and the like are used. You. In addition, when the insulating property is not important, metal powder such as aluminum, copper, silver, and gold, silicon carbide powder, graphite powder, and the like can be used in addition to the above ceramic powder. The shape of the heat conductive filler may be any shape such as a sphere, a needle, and a plate. Particle size, average particle size 0.5
の も の 100 μm is used.

Next, the flexible heat radiation spacer of the present invention comprises:
At least one surface has an uneven portion. The uneven portion in the present invention refers to a portion having a distance from the vertex of the convex portion to the low point of the concave portion of 30 to 100 μm. If this distance is smaller than 30 μm, it will be in close contact with the surface of the heat radiating component and the repairability will be poor.

The ratio of the uneven portion is 50 to 90% of the surface area of the surface having the uneven portion as the total occupied area ratio. If it is more than 90%, the repairability will deteriorate, and 50%
If it is less than 1, the thermal resistance increases. The width of one concave or convex portion is preferably about 10 to 0.1 mm ² as its plane area.

The planar shape of the concave portion or the convex portion may be a polygon such as a triangle, a quadrangle, a pentagon, a circle, an ellipse, or the like.
There are no particular restrictions. Further, the cross-sectional shape of the concave portion or the convex portion may be a curved surface such as a spherical surface, a triangle, a square, or a combination thereof. The irregularities may be provided on at least one of the heat radiation spacer surfaces.

Further, the flexibility of the flexible heat radiation spacer of the present invention is such that when a load of 98 KPa is applied, the compression ratio of the surface layer defined as a portion from the surface to 20% of the total thickness is 1% of the total thickness. ５5%, and the difference from the overall compression ratio is 20% or less. When the compression ratio of the surface layer is less than 1%, the handleability is improved, but the adhesion is reduced, and the contact thermal resistance with the surface of the heat-generating component is increased. When the compression ratio of the surface layer is more than 5%, both the handleability and the repairability deteriorate.
On the other hand, if the difference from the overall compression ratio is more than 20%, the stiffness of the heat radiation spacer is reduced, and the handling property is reduced.

Particularly preferred flexibility is within the range of the compressive properties of the surface layer, and the overall compressibility is 10% or more, especially 20% or more with respect to the original thickness. If the overall compression ratio is significantly smaller than 10%, not only the adhesion to the heat-generating electronic component and the shape follow-up property will be degraded, but the heat radiation characteristics will deteriorate, but also the load on the heat-generating electronic component will increase, resulting in heat generation. It is not preferable because it may cause damage to the electronic component.

Further, the flexible heat radiation spacer of the present invention comprises:
A reinforcing material such as a glass cloth or a carbon fiber cloth can be contained within a range that does not impair the flexibility and the thermal conductivity.

The thermal conductivity of the flexible heat radiation spacer of the present invention is preferably 1.0 W / m · K or more, particularly preferably 1.5 W / m · K or more.

The thickness of the flexible heat radiation spacer of the present invention is generally from 0.3 to 10 mm, preferably from 0.5 to 6 mm. Its plane shape is a triangle,
There are no particular restrictions on polygons such as quadrangular and pentagonal, circular, elliptical and the like.

Further, it is preferable that at least one of the surfaces of the flexible heat radiation spacer of the present invention is subjected to a non-adhesive treatment, particularly to a surface having irregularities. Examples of the non-adhesive treatment include irradiation with ultraviolet rays and powdering with BN powder.

One example of the method for producing the flexible heat radiation spacer of the present invention is as follows. One-part silicone or an organopolysiloxane having a vinyl group at the terminal or side chain and two or more H atoms at the terminal or side chain. A slurry is prepared by mixing a thermally conductive filler powder with a two-part silicone with an organopolysiloxane having a Si group. The prepared slurry is divided into two, and one is used as a first liquid, and the other is used as a second liquid by adding an appropriate amount of a curing agent containing an organosiloxane having low molecular weight Si-H as a main component. After defoaming with a vacuum defoaming device or the like, the slurry of the second liquid is applied to a predetermined thickness with a doctor blade on a fluororesin film having appropriate irregularities, and before it is cured, the The slurry of the first liquid is applied on the upper surface with a doctor blade to a predetermined thickness. Then, after heating to cure the silicone, while attaching a PET film to the surface,
The heat radiation spacer is transferred to the PET film side by peeling off the lower fluororesin film.

The total occupied area ratio of the unevenness and the depth of the unevenness can be determined according to the uneven shape of the base film used. As the base film, a resin film or a rubber sheet having heat resistance of 120 ° C. and having irregularities in which the total occupied area ratio of the irregularities is 50 to 90% with respect to the surface area of the surface having the irregularities is used. Is done. In particular,
A composite formed with a glass cloth or the like is preferable.

If the viscosity of the uncured silicone composition comprising the heat conductive filler and the silicone rubber is less than 20 Pa · s, the casting method is used.
In the case of 120 Pa · s, the doctor blade method, 120
When it is higher than Pa · s, a press molding method is preferred. At the time of thickening, fine powder of silicon oxide having a size of tens to several hundreds μm or ultrafine powder such as Aerosil is used.

As the heating and curing device, a general heating device such as a continuous hot-air drying oven, a far-infrared drying oven, or a batch-type hot-air dryer can be used. Preferably, it is a continuous heating device from the viewpoint of productivity.

[0026]

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

Example 1 From silicone A liquid (organopolysiloxane having a vinyl group at a terminal or side chain) and silicone B liquid (organopolysiloxane having at least two or more H-Si groups at a terminal or side chain) Two-component addition polymerization type liquid silicone (trade name “S” manufactured by Dow Corning Toray Co., Ltd.)
E-1885 ") and silicon nitride powder (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name" F-2 ") having an average particle size of 28 m were mixed at a ratio shown in Table 1 to prepare a slurry having a viscosity of 80 Pa.s.

This was divided into two parts, and one of them was added with a curing agent composed of a low molecular weight organosiloxane having an H-Si group (trade name “RD-1” manufactured by Dow Corning Toray Co., Ltd.), and the first liquid was added. Was adjusted. The remaining slurry (to which no hardener is added) is used as a second liquid, and the first and second liquids are defoamed by a vacuum defoaming machine, and then irregularities are uniformly formed on one surface of the heat radiation spacer. For the purpose, the first liquid is first applied thinly with a doctor blade on the entire surface of a glass cloth composite fluororesin film (Nitto Denko Corporation, trade name "Nitoflon Tape"), and then the second liquid is applied to the first Full thickness 1 on liquid
mm. After heating this at 120 ° C. for 10 minutes, a PET film was adhered, and the lower layer of the fluororesin film was peeled off and transferred to the PET film. Thereafter, the silicone was further cured by heating at 120 ° C. for 22 hours to produce a flexible heat radiation spacer having an uneven surface.

Example 2 Instead of silicon nitride powder as a heat conductive filler,
Boron nitride powder having an average particle diameter of 7 μm (trade name “GP” manufactured by Denki Kagaku Kogyo Co., Ltd.) and aluminum oxide powder having an average particle diameter of 10 μm (trade name “AS-50” manufactured by Showa Denko KK)
Were mixed in the proportions shown in Table 1, and a slurry having a viscosity of 100 Pa · s was prepared in the same manner as in Example 1 to produce a flexible heat radiation spacer.

Example 3 A device was manufactured in the same manner as in Example 1 except that a fluororesin-based film having a different shape of the uneven portion was used.

Comparative Example 1 A heat radiation spacer was manufactured in the same manner as in Example 1 except that a fluororesin-based film having no irregularities was used as the base resin film.

Comparative Example 2 A second liquid was used instead of the first liquid (therefore, the first coating,
A heat radiation spacer was manufactured in the same manner as in Example 1 except that only the second liquid was used in the second coating).

Comparative Example 3 A heat radiation spacer was produced in the same manner as in Comparative Example 2, except that a fluororesin film having no unevenness was used as the base resin film.

With respect to the obtained heat radiation spacer, the thermal conductivity, flexibility (compression rate), and the total occupied area ratio of the uneven portions were measured according to the following. In addition, the handleability and repairability of the heat radiation spacer were also evaluated. Table 2 shows the results.

(1) Thermal conductivity The heat radiation spacer is cut into a TO-3 shape, which is cut into a TO-
After sandwiching between a 3 type copper heater case and a copper plate and setting with a tightening torque of 200 g-cm, 5 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 (° C.) ) Is measured, and a thermal resistance (° C./W) is obtained by an equation [temperature difference (° C.) / Power (W)].
Next, the thermal conductivity (W / m · K) was calculated by the formula [thickness (m) / {thermal resistance (° C./W)×measured area (m ² )}].

(2) Flexibility (compression rate) A 98 KPa stress is applied in the thickness direction to a 1 cm ² portion of the heat radiation spacer by a universal tensile tester (trade name “Autograph” manufactured by Shimadzu Corporation) to compressively deform. Measure the quantity,
Formula [compression deformation (mm) x 100 / original thickness (mm)]
, The overall compression ratio was calculated. The compression ratio of the surface layer is
A test piece having a thickness corresponding to 20% of the total thickness was cut out from the surface of the heat radiation spacer and measured.

(3) Total occupied area ratio of uneven portions On the surface of the heat radiating spacer where the uneven portions exist, any 10
Microscopic photographs are taken in three regions (one field of view: 3 cm ² ), the area ratio of the uneven portion per 1 cm ² is measured, and the average value is converted into the area of the surface having the uneven portion to calculate the occupied area ratio. did. In addition, when the surface of the heat radiating spacer has uneven portions unevenly, the measurement was performed by expanding the measurement region and the measurement point.

(4) Handleability The handleability of the heat radiating spacer having a shape of 50 × 50 mm was judged by finger touch. "O": Good handling, no deformation even when lifted by hand. “×”: poor handling, deformed when lifted by hand.

(5) Repairability A heat-dissipating spacer having a shape of 50 × 50 mm was adhered to a mirror-finished aluminum plate and peeled off. "O": Can be easily peeled off without deformation. “×”: Deformed and cannot be easily peeled.

[0040]

[Table 1]

[0041]

[Table 2]

From the table, it can be seen that the flexible heat radiation spacer of the example of the present invention is superior in all of thermal conductivity, flexibility, handleability and repairability as compared with the comparative example.

[0043]

According to the present invention, there is provided a flexible heat radiation spacer having improved handleability and repairability without deteriorating flexibility and thermal conductivity.

That is, since the flexible heat radiation spacer of the present invention has an uneven portion on at least one surface thereof, it can be easily removed from the heat-generating component after being attached. In addition, since layers having different hardnesses are integrated, handling is good. Furthermore, since it has high thermal conductivity and high flexibility, there is very little risk of damaging the heat-generating electronic component even when pressed against the heat-generating electronic component, which is very weak against stress.

Claims (2)

[Claims] 1. A cured silicone material filled with a thermally conductive filler, wherein at least one surface has an uneven portion, and the total occupied area ratio of the uneven portion has the uneven portion. The compression ratio of the surface layer is 50 to 90% of the surface area of the surface, and when a load of 98 KPa is applied, the compression ratio of the surface layer defined as a portion from the surface to 20% of the total thickness is 1 to 5% of the total thickness. And the difference from the overall compression ratio is 2
A flexible heat radiation spacer characterized by being at most 0%. 2. The flexible heat radiation spacer according to claim 1, wherein the overall compression ratio is 10% or more and the thermal conductivity is 1 W / m · K or more.