JPS63186881A - Production of metallic sheet having large heat radiating area - Google Patents

Abstract

PURPOSE:To produce a metallic sheet having a large heat radiating area, by coating a solderable metallic sheet with creamy solder, spreading metal powder having high heat conductivity on the solder and heating the sheet to roughen the surface. CONSTITUTION:A solderable copper sheet 1 is coated with creamy solder obtd. by kneading solder powder with a flux. Copper powder 2 of about 250 mesh particle size or short copper fibers of about 0.01mmphi are spread on the solder and the sheet 4 is heated in a reflow furnace 3 to roughen the surface. Thus, a copper sheet having a remarkably increased surface area is obtd. and the heat radiating effect is enhanced.

Description

[Detailed Description of the Invention] Purpose of the Invention As the electronic industry becomes more and more diseased, there is an increasing tendency to mount a large number of various components in a narrow space, and as a result, the temperature of the mounting board due to Joule heat increases. It has become impossible to ignore it. For this reason, aluminum metal substrates with good thermal conductivity (which form an alumina oxide film on the surface) are about to be adopted as substrates in the semiconductor industry in place of conventional plastic substrates such as 7-dinol resin. .

Such a thing is desired not only in the electronic industry, but also in measuring instruments through which electric current flows and in the mechanical industry that involves the generation of frictional heat. In short, the idea is to significantly increase the surface area of a single smooth metal surface and increase the heat dissipation effect as much as possible in proportion to the expanded area.

Prior Art> In order to increase the metal surface area per unit area, the following methods have conventionally been used.

(1) As seen with aluminum foil electrodes in electrolytic aluminum capacitors, overcurrent anodic electrolytic polishing of aluminum foil is performed by
(2) Make the surface as porous as possible by making scratches on the metal surface using a metal wire brush or the like to mechanically expand the surface area, or apply rough processing such as embossing. 3) Attaching a large number of metal legs to a metal surface to increase the heat dissipation effect, (4) Attaching fins to the heat dissipation part to increase the heat dissipation area, as in a car radiator or electric refrigerator, (5) Like stainless steel. (6) Laminating a copper plate with good thermal conductivity on a metal with poor thermal conductivity; (6) Attaching a water-cooled glossy kerato for direct cooling;
Things like this were considered.

The above-mentioned measures cannot be directly applied to substrates used in electronics. This is because the board is used in a narrow space at the end, and it is difficult to cool it from the outside, so it is required to use it under the same conditions as those currently in use as much as possible. . Moreover, it can be said that there is a limit to the expansion of area when using machining.

The present invention attempts to increase the heat dissipation area by a unique method that has not been thought of before.

The present invention to solve the above problems〉 Cream solder (kneaded product of solder powder and 7 lac)
Coat a thin layer of copper or nickel on a copper plate or nickel plate, and sprinkle fine copper powder on it until it dries. Shake off the excess copper fine powder, except for the tM powder that has stuck due to the adhesive force of the cream solder. .

In this way, powder is scattered on the surface of lj
7 Heating in a C1-furnace (an electric furnace that raises the temperature in a short time and performs soldering in a short time).

At this time, the same effect can be achieved even if 9g metal fiber is used instead of metal powder. In this way, the surface of the copper plate becomes rough and has many extremely fine irregularities, and its surface area can be expanded by more than 100 times at once. At this time, it is best to use copper powder with a size of around 250 mesh,
Even if particles with a relatively large particle size of 100 mesh or more are used, the effect can be improved. The same effect can also be obtained by using short copper fibers made by cutting thin copper wires of about 0.01-φ.

<Example> The working steps of this method are shown in tlS1 diagram.

Copper foil is bonded to the back of the board, cream solder is applied to this body foil, and 250 mesh fine copper powder is sprinkled on top of this. ffi due to the adhesive strength of cream solder
After shaking off the copper powder other than those deposited, it is heated in a 970-degree furnace with an fA temperature of 200°C. As a result, the copper powder becomes densely attached to the copper plate. The temperature of the product thus produced was raised to 120°C, and the cooling rate thereafter was measured. The results are shown in Figure 2.

As you can see in this figure, compared to just a single body plate, about 1
/ Cool quickly for 2 hours or more. In other words, the cooling effect is doubled.

A method may also be used in which a large copper plate is used, one side of which is previously subjected to the same treatment as in the present invention, and the copper plate is cut into a predetermined shape and pasted to a location that requires cooling.
For such applications, in order to cool the IC board,
The effect can be exhibited by attaching the plate of the present invention to the back surface of an IC board using an adhesive.

4. Description of the Drawings Fig. 1 is an explanatory diagram showing the working process of the present invention, and Fig. 2 is a measurement result diagram showing the cooling effect of the product of the present invention.

1・・・・・・・・・・・・Copper plate, 2・・・・・・・・・・・・
Copper powder, 3...70-Furnace 4...
······substrate.

""""'""'Jb1. : FETUS,,
, l-) Figure 1 °C Figure 2 Procedural amendment (method) April 1986 ≠ date

Claims (1)

[Claims] Apply cream solder (cream-like mixture of solder powder and flux) onto a solderable metal plate, place metal powder or metal fiber with good thermal conductivity on top of it, and solder in this state. A method for manufacturing a metal plate with a large heat dissipation area, which is characterized by roughening the metal surface by raising the temperature.