JPS6036091B2 - Method for manufacturing harmech seals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a hermetic seal using a metal such as tantalum, titanium, or the like that is formed into an arm in a heated atmosphere containing an active gas.

For example, regarding hermetic seals using tantalum leads used in tantalum electrolytic capacitors, tantalum is a stable metal with a high melting point of about 3,000 OO and corrosion resistance equivalent to that of platinum, but in a heated atmosphere of about 40,000 oo or more. It has the disadvantage that it easily absorbs active hydrogen and oxygen, and if even a small amount is incorporated, it can cause arm formation and become brittle.

This is not limited to tantalum, but titanium, monbudene, zirconium, etc. have similar drawbacks. In the production of glass hermetic seals, glass strands are bonded by heating the welding furnace to around 100,000 degrees Celsius, so measures must be taken to prevent active gases such as hydrogen and oxygen from forming.

For this reason, conventional port-arrival processing has been carried out in a vacuum of 10-4 tons or less, or in an inert gas such as high-purity argon or helium. However, in the secondary vacuum method, although the tantalum lead does not form into arms, the air pressure inside the welding furnace is almost 0, so bubbles are generated from the molten glass, and the bubbles remain in the glass after cooling. The drawback is that if force is applied to the tantalum lead, the glass may break or the airtightness of the welded area may deteriorate.

On the other hand, the method of carrying out in a high purity inert gas is
-88110, etc., but with this method, the inside of the furnace is filled with inert gas, so no bubbles are generated from the glass.

However, even if argon gas with a purity of 99.99% is used, the tantalum lead becomes brittle due to slight impurities such as hydrogen and oxygen, and the tantalum lead easily breaks. To prevent this, it is necessary to further improve the purity of the argon gas, but obtaining a higher purity gas would be extremely expensive and impractical. The method of the present invention has improved these drawbacks, and an example of the method will be described below. First, the hermetic seal to be welded is a ring made of a corrosion-resistant metal such as tantalum or stainless steel, as shown in Figure 1. Glass powder (in this example, shelving glass N manufactured by Corning Co., Ltd.
o. A cylindrical glass 2 made by calcining and hardening (using 7052) is fitted, a tantalum lead 3 is passed through the hole in the center of the glass 2, and this is attached to a carbon jig 4 as shown in Figure 2.
The welding process was carried out by attaching it to a welding furnace and placing it in a welding furnace.

The process of settling treatment is shown according to the temperature change diagram in Figure 3.
It consists of the following steps.

(1) Place the hermetic seal in the welding furnace and clean the inside of the furnace.
Evacuate to a vacuum of 0-4 Torr or less.

(0) Start heating and bring the inside of the furnace to around 1000o○. (
In this example, the glass 2 is melted by leaving it for 3 to 10 minutes.

(N) High purity inert gas (99.99% in this example) into the furnace
(Argon gas) is injected to about normal pressure. (V) After injecting high-purity inert gas and leaving the furnace for 2 to 4 minutes, cooling of the furnace is started, and when the temperature is lowered to around 700 qo in 1 to 2 minutes, it is evacuated again to vacuum. (W) Keep the inside of the furnace at a vacuum of 10-4 Torr or less and gradually cool it to room temperature using the usual method. The manufacturing method according to the present invention, which is carried out through the above steps, is characterized by melting glass in a vacuum, and using a high-purity inert gas atmosphere only for the minimum amount of time necessary to eliminate bubbles generated in the molten glass. Then, when cooling begins and the temperature drops a little and the viscosity of the glass increases and there is no risk of bubbles reoccurring, it is evacuated again. It is something that can be prevented.

As the next practical example, hermetic seals were manufactured using the method of the present invention and the method of the subordinate method, and the difference in performance was investigated, as shown in Table 1.

Use the same hermetic seal, melting furnace, etc.
'a) All treatments were performed in a vacuum of 104 Torr or less. {b) All treatments were performed in 99.99% pure argon gas. 'c) of the method of the invention. (However, the inert gas injection time was deviated by 3.
) One hard hermetic seal was manufactured under each of these five conditions, and the tantalum lead was tested for bending and the presence or absence of air bubbles in the glass was examined. Table 1*1 The number of bends (average of 10 leads) is calculated by bending the tantalum lead to a right angle and returning it to its original position once.

Note that the number of times the tantalum lead was bent before treatment was 10.5 times. *2 For bubble generation, the glass was visually inspected and the number of bubbles observed was counted. (Solid medium of No. 1) As is clear from these results, although there was no problem with the number of bends for examining the verticalization of the glass treated in vacuum in 'a}, air bubbles were observed in all the glasses.

Further, in the glass treated in argon gas ('b), no bubbles were observed in the glass, but the tantalum lead was bent 1.3 times and the tantalum leads were severely formed into arms. In the method of the present invention (c), good results were obtained in both the number of bends and the generation of bubbles. However, if the argon gas injection time was about 1 minute, some bubbles remained. After about 5 minutes, the effect of embrittlement appears and the number of bends decreases, so in this example, the optimal time for argon gas injection was 2 to 4 minutes.However, the optimal time for inert gas injection The value varies depending on the conditions such as the melt volume of the welding furnace, the pressure of the injection gas, and the purity.The hermetic seal manufactured by the method of the present invention does not decompose the tantalum lead and has no air bubbles in the glass. Since there is no occurrence of this, sufficient strength and airtightness can be obtained, and it can be used in applications that require high reliability.

In addition, the number of defective products during manufacturing is reduced, and the yield of the process is improved. Although the embodiment described a method for manufacturing a hermetic seal using tantalum lead, the present invention is not limited to tantalum, but can also be applied to lead metals such as titanium, zirconium, and molybdenum, which become brittle in a glass welding atmosphere containing active gas. It can also be applied to the method of manufacturing the hermetic seal used.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing each part of the hermetic seal of the present invention, Fig. 2 is a sectional view showing the hermetic seal of the present invention attached to a carbon pick-up tool, and Fig. 3 is a perspective view showing each part of the hermetic seal of the present invention. FIG. 3 is a temperature change diagram showing temperature changes in the welding furnace. 1...Sealing plate, 2...Glass, 3...Tantalum lead,
4...Carbon feeding shell. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A method for manufacturing a hermetic seal in which a lead made of one or more selected from tantalum, titanium, molybdenum, zirconium, or niobium, or a lead made of an alloy containing one or more of these metals is welded with glass. The glass is melted in a vacuum, high-purity inert gas is injected in the molten state, cooling is started while maintaining the inert gas atmosphere, and the glass is evacuated to vacuum again during cooling. Method for manufacturing hermetic seals.