JPS6076274A - Brazing method using aluminum - Google Patents

Abstract

PURPOSE:To improve reliability of brazing and to reduce cost by cleaning ultrasonically the surface of an Al material to be used as a brazing material in water contg. quartz powder prior to a brazing stage then treating chemically said surface. CONSTITUTION:A glass vessel 8 contg. pure water 7 is disposed in a water tank 6 provided with an ultrasonic oscillator 5. Quartz powder 9 is put into the vessel 8 and diode chips 1, etc. each having an Al layer 2 deposited by evaporation are put into the vessel 8. The quartz powder 9 which receives energy from the oscillator 5 collides against the surface of the layer 2 and removes the oxide film of the Al surface. The activated Al surface is thus obtd. If the Al layer is subjected to etching by an ordinary chemical treatment after such treatment, the fresh Al surface having the uniform condition is obtd. and stable brazing with metallic electrodes 4, etc. is accomplished. The reliability of brazing is improved and the reduction of the cost owing to an improvement in yield is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a brazing method using aluminum, which is performed, for example, for bonding a silicon chip and a metal electrode during the manufacture of semiconductor devices.

[Prior art and its problems]

It is well known that high-temperature brazing is used to bond silicon chips to lead wires or metal electrodes such as substrates, and to obtain ohmic contact using aluminum as a brazing material. It is applied to glass-sealed general diodes, high-speed diodes, high-voltage diodes, etc. However, when At, which is a brazing material, is left in the atmosphere or heat treated, an oxide film is formed on the surface, reducing the properties of the brazing material. A chemical etching process is performed. However, with this chemical treatment, the etching rate varies depending on the degree of oxidation of the At surface, so it is difficult to obtain a surface in a constant state, and brazing has the drawback of unstable yield.

[Purpose of the invention]

An object of the present invention is to provide a method that, when using KT whose surface has been oxidized as a solder, removes the oxide film to generate an activated surface and performs highly reliable brazing. .

[Key points of the invention]

According to the present invention, the surface of the At material used as the brazing material is ultrasonically cleaned in water containing quartz powder before the brazing process, and then further chemically treated to obtain a uniform and activated brazing surface. It will be done.

[Embodiments of the invention]

FIG. 1 shows a high-voltage silicon diode as an example of a semiconductor device in which the brazing method according to the present invention is carried out, and each high-voltage diode chip 1 is made by stacking silicon plates each having a PN junction formed thereon, and then distilling At on both surfaces. Then, it is created by gJl'M in the shape of a dice perpendicular to the board surface. Therefore, both sides have the A1 layer 2. This A117 is melted and brazed to the electrodes 4 made of molybdenum, tungsten, etc. at the tips of the lead wires 3 on both sides. Second
The figure shows an ultrasonic cleaning apparatus according to an embodiment of the present invention, in which a water tank 6 is equipped with an ultrasonic oscillator 5 of, for example, 300 to 500 W, and a water tank 6 containing, for example, 500+J of pure water 7 is deposited on both ends of the ultrasonic cleaning apparatus. High voltage diode tinog 1 with layer 2 300
When 0 to 5000 pieces are accommodated, the quartz powder 9 receives energy from the ultrasonic oscillator 5 and hits the surface of the kt layer 2, and is activated to remove the oxide film formed on the Aja surface. A hardened At surface can be obtained. The ultrasonic cleaning time is preferably about 10 to 15 minutes, and even if the ultrasonic cleaning is carried out for a longer time, the effect will not increase. After this, lead wire 3
Chemical treatment similar to that traditionally applied immediately before combination with.

In other words, if etching is performed using K such as HF, KOH, or NaOH, the etching will always be performed in the same way.
A fresh At surface in a uniform state is obtained, which is melted by subsequent heating, allowing uniform brazing and stable brazing to the surface of the metal electrode 4.

FIGS. 3 and 4 show the reduction in visual inspection braze failure rate and thermal resistance failure rate for 200 brazes, respectively, when the present invention is practiced.

The invention is not limited to the case where the At brazing layer as described above is provided on the object to be brazed in advance, but also the case where the At foil or if At
It can also be applied to surface activation of At brazing material when a plate is sandwiched between objects to be brazed.

〔Effect of the invention〕

In the present invention, the oxide film on the surface of A/L used as a brazing material is removed by ultrasonic cleaning in water containing quartz powder, and then chemically treated to generate a fresh activated At surface. Since brazing can always be performed with a uniform surface condition, the reliability of brazing is improved, and brazing can reduce manufacturing costs by improving yields.Moreover, mass processing is possible, especially for silicon chips and metal electrodes. The effect obtained during high-temperature brazing is significant. In addition, as a result of this, for example, even if a silicon chip is left for a long time after M vapor deposition, an oxide film that is formed can be removed at any time, which is advantageous in terms of production control.

[Brief explanation of drawings]

FIG. 1 is a front view showing a high-pressure silicon diode as an object of an embodiment of the present invention, FIG. 2 is a sectional view of an ultrasonic cleaning device in an embodiment of the present invention, and FIG. Attached is a diagram showing a decrease in the defective rate, and FIG. 4 is a diagram similarly showing a decrease in the thermal resistance defective rate. 1... High voltage diode chip, 2... kt vapor deposition layer,
Sai1(2)? 3 flash 2 flash 40

Claims (1)

[Claims] 1) A method for brazing using aluminum, which is characterized in that the surface of an aluminum material as a brazing material is ultrasonically cleaned in water containing quartz powder before the brazing process, and then further chemically treated.