JPS5914119B2 - Heat sink surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface treatment of a heat radiator for improving the heat transfer coefficient of a heat radiator for boiling cooling.

Boiling cooling is a cooling method that removes heat from a heat radiator using the latent heat of the refrigerant.If you compare the heat transfer coefficient on the surface of the heat radiator with conventional cooling methods that use convection heat transfer from air, oil, etc., it is an order of magnitude better. represents a characteristic. For this reason, the boiling cooling method generates a large amount of heat from a small surface area and is suitable for cooling high-power semiconductor devices and the like with a high heat flow rate. In this boiling cooling, the boiling heat transfer coefficient improves as the generation and growth of bubbles on the heat transfer surface becomes more active. For example, by forming cavities as shown in FIG. 1 on the surface of the heat sink to make it porous, the generation and growth of bubbles will be activated and the boiling heat transfer coefficient will be improved as shown in FIG. In Fig. 2, the characteristic ^ indicates that the heat dissipation surface is flat, and the characteristic ('' indicates that it has a cavity.In boiling on a flat surface, the entire liquid 5 near the heat dissipation surface is heated, and the liquid around the bubbles is heated. Bubbles grow by heating the surface.On the other hand, on a surface with cavities, the bubbles grow within the cavity, so the liquid film around the bubbles is easily absorbed even if the entire liquid does not become superheated because the liquid film inside the cavity is thin. As a result, the growth of bubbles becomes active and the boiling heat transfer coefficient increases.In other words, a deep cavity with a narrow opening exists in a solid wall with a large specific heat, density, and heat transfer coefficient. , a high boiling heat transfer coefficient can be obtained when the heat flux is large.15 Conventionally, a cavity as shown in FIG. 1 was formed by machining or plating.

However, machining has the disadvantage that it is extremely difficult and costly. Furthermore, the method of physically roughening the surface of the heat sink and plating it has the disadvantage that it is difficult to consistently obtain excellent boiling characteristics because the shape of the cavity is not constant. The present invention has been made to solve the above-mentioned drawbacks, and by forming islands of paint and plating, a heat dissipating body having excellent boiling properties can be obtained. It is related to. An example of the present invention is shown in FIG. As shown in FIG.
A plurality of layers are formed and then plated to form a plating film 3 as shown in FIG. 3b. 30 The paint is then dissolved with a stripper, forming a narrow cavity 4 with an opening 4a.

In order to form the islands 2, a plate (not shown) having a plurality of micropores (not shown) is brought into contact with the surface of the heat radiation surface 1a, and paint is sprayed onto the plate (not shown). When plating is performed with the 35 islands 2 formed, the metal surface is not plated because the parts to which the paint is applied are insulated, and the plating layer becomes porous as shown in FIG. 3b. Next, by dissolving and removing the coating film adhering to the metal surface using a coating film stripping agent, the cavity 4 is formed into the shape shown in FIG. 3c. When creating a boiling nucleus, when the base material of the heat sink 1 is copper, copper plating is effective, and copper sulfate plating, which has poor throwing power, is best.

The paint is a clear color containing no inorganic pigments and colored with organic pigments, and nitrocellulose, shellac, alkyd, vinyl, etc., which have poor solvent resistance, are effective. Solvent-based paint strippers are effective. Next, specific examples of the present invention will be shown.

Example 1 After cleaning the heat dissipation surface of a heat dissipation body made of copper as a base material by alkaline degreasing and pickling, etc., a plate having a large number of penetrating fine holes with a diameter of approximately 30 μm was brought into contact with the heat dissipation surface, and vinyl resin enamel was applied. Spray with a spray gun and let dry naturally.

Next, copper sulfate 2609/t, sulfuric acid 809/t, temperature 30℃
50 at 5A/Dm2 with air agitation under the conditions of
When plating was carried out, a porous plating film of about 50 μm was obtained. Furthermore, in the stripping agent whose main component is methylene chloride, 2
The coating film was dissolved and removed by immersion for 0 minutes to obtain a heat sink having the shape shown in FIG. 2c. Example 2 After cleaning the heat dissipation surface of a heat dissipation body made of copper as a base material by alkaline removal FJ pickling, etc., a plate having a large number of penetrating fine holes with a diameter of about 40 μm was brought into contact with the heat dissipation surface, and an oil-based Spray the enamel with a spray gun and let it dry naturally.

Next, copper sulfate 2609/t, sulfuric acid 809/t, temperature 30℃
70 at 5A/Dm2 with air agitation under the conditions of
When plating was carried out, a porous plating film of about 70 μm was obtained. Furthermore, the heat sink having the shape shown in FIG. 2c was obtained by immersing it in toluene, a paint film remover, for 20 minutes to dissolve and remove the paint film. According to this invention, a cavity with a uniform shape can be easily obtained by forming minute islands of paint on a heat dissipation surface, plating, and then removing the paint to form micropores. I can do it.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing a heat sink obtained by a conventional surface treatment method, Figure 2 is an explanatory diagram showing the thermal resistance characteristics of the heat sink, and Figure 3 is an explanatory diagram showing the thermal resistance characteristics of the heat sink.
The figure is a sectional view illustrating an embodiment of the present invention.

Claims (1)

[Claims] 1. Forming a plurality of minute islands of paint on the heat dissipation surface of the heat dissipation body,
A method for surface treatment of a heat radiating body, comprising plating the heat radiating surface and then removing the paint to form predetermined micropores in the heat radiating surface. 2. The heat radiator according to claim 1, wherein the paint islands are made by bringing a plate having a plurality of micro holes opened at predetermined intervals into contact with the surface of the heat radiator to adhere the paint. surface treatment method.