JPS6225440A - Thermal conductive sheet for electric part - Google Patents

Abstract

PURPOSE:To obtain a chemically stable sheet with high thermal conductivity by coating silicone rubber on a sole graphite sheet or one or both sides of the graphite sheet. CONSTITUTION:A graphite sheet is coated solely or on one or both sides with room temperature curable rubber to obtain a chemically stable heat sink sheet with high thermal conductivity. This sheet 1 is mounted by the adhesive of a silicon rubber layer 6 on a fullback transistor 2. The heat of the transistor 2 is transmitted to the plate 1, and dissipated out by a heat sink fin 5.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a thermally conductive sheet, particularly a thermally conductive sheet for electrical components for heat dissipation attached to heat-generating electronic components such as transistors, diodes, etc. It is related to.

(Conventional technology) Conventionally, when installing heat-generating electronic components such as transistors and diodes, heat dissipation grease or thermally conductive electrical insulation sheets are used to insulate them from heat sinks and radiate heat. However, with advances in electronics-related technology, recent transistors have become generally insulated, with the entire transistor sealed with epoxy resin (- is called a full back transistor).

For this reason, full-back transistors (for both of them, grease application and heat dissipation sheets are no longer required for low power loads, but grease application and heat dissipation sheet installation are still considered essential for high power loads). There is.

However, this process of applying grease is complicated and involves stains (it is worshiped by people who have lost their lives), so automation of the process is being considered, but it has the disadvantage that it is difficult to automate. Regarding heat dissipation sheets, since the transistor is a full pack, insulation is not necessary and only thermal conductivity is an important factor, so metal plates such as gold, silver, copper, and aluminum, beryllium oxide, and nitride are The use of oxides and compounds such as borium and alumina is also being considered, but these have the disadvantage of being expensive, easily oxidized, or toxic; There is a demand for a heat dissipating sheet that is inexpensive and chemically stable.

(Structure of the Invention) The present invention relates to a thermally conductive sheet for transistor heat dissipation that can meet the demands of the industry as described above. It is characterized by the fact that

That is, as a result of various studies on heat dissipation sheets that have high thermal conductivity and are chemically stable, the inventors have found that a graphite sheet has a thermal conductivity α410aj/c7rL・sec・℃, which is 0.49 Cal/an− compared to aluminum. It is close to -°C and is a general-purpose material used in various fields, so it is inexpensive. (2) This graphite sheet coated with silicone rubber on one or both sides of the sheet does not cause any increase in thermal resistance; The present invention was completed by confirming that the present invention has the advantage of facilitating the immobilization of .

Next, this will be explained based on the attached drawings.

Figure @1 shows a cross-sectional view of the heat sink of a full-pack transistor using the thermally conductive sheet of the present invention.
Usually, this is said to have a thickness of 0.1 to 1 mm, but since the heat sink 1 made of this graphite sheet is fixed to the bottom of the full-pack transistor 2 with screws 3 and nuts 4, this full-pack transistor 2 Since the heat sink 1 has excellent thermal conductivity, the heat generated by the heat sink 1 is immediately absorbed by the heat sink 1.
The heat transferred to the heat sink 1 is released outside the system by the heat sink fins 5 and the like.

In addition, Fig. 2 is a cross-sectional view of one side of the heat dissipation sheet 1 covered with silicone rubber 6, which shows that when the heat dissipation sheet 1 is attached to a full-pack transistor as shown in Fig. v') The adhesive strength of the cone rubber layer 6 provides the advantage of ease of installation. This silicone rubber may be any commercially available silicone rubber such as room temperature curing silicone rubber or thermosetting silicone rubber, but heat-curable solvent-free liquid silicone rubber is used because it has high thermal conductivity. This is said to be preferable from the viewpoint of ease of use. In addition, in order to improve the adhesion of the silicone rubber to the graphite sheet, it is recommended to apply a brimer to the graphite sheet in advance. This can be done by coating, calendering, or spray coating.

Next, examples of the present invention will be given.

Example Graphite sheet/graph oil plain sheet with a thickness of 0.127 m and a width of 152 H [trade name manufactured by UQQ, USA] [hereinafter abbreviated as GTB-1], one side of this GTB-1 was coated with room temperature curing silicone rubber.・This GTB was coated with 20μ of KE1204RTV (Shin-Etsu Chemical Co., Ltd. product name) using an applicator (hereinafter abbreviated as GTB-1).
Room temperature curable silicone rubber on both sides of -1 Kg 120
4 Prepare RTV (mentioned above) applied to a thickness of 15μ with an applicator (hereinafter abbreviated as GTB-1),
These were sandwiched between the transistor 2SD1487 (product name made by Matsushita Electronics Co., Ltd.) and the fin FBA-150-PS (product name made by Ornis Co., Ltd.), and attached using a torque screwdriver. Using heat dissipation grease ()-746 [Shin-Etsu Chemical Co., Ltd. mounting product name] on the fins,
Thermal resistance after 1 minute when a force of 0 V and 3 A is applied (
”C/W) Transistor Transient Thermal Resistance Measuring Instrument TH-1
When measured with 5fi [product name manufactured by Kuwano Electric Co., Ltd. J Co., Ltd.],
The results shown in Table 1 below were obtained.

Table 1 (Note: Calculation of thermal resistance value 1 0<V>
: Temperature coefficient of VER of transistor (ΔVEB/ΔT
(2.2mV/℃) α: Correction term by base Tsuchiura (0.9ω in α)

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a transistor and a fin in which the thermally conductive heat sink of the present invention is incorporated, and Fig. 2 is a longitudinal cross-section of a transistor and a fin in which a thermally conductive heat sink coated with silicone rubber on one side is incorporated. The figure is shown below. 1... Heat sink, 2... Transistor, 5...
Heat dissipation fin, 6...Silicone rubber 1m.

Claims (1)

[Claims] 1. A thermally conductive sheet for electrical components, characterized by being made of a graphite sheet alone or coated with silicone rubber on one or both sides of the sheet.