JPS62150628A - Connecting structure of ceramics and metal - Google Patents

Abstract

PURPOSE:To obtain an inexpensive electron tube without producing a metalized film over a ceramics, by forming a fitting step at the ceramics and soldering a metallic tube with a solder containing an active metal. CONSTITUTION:At a stem ceramics 8 is furnished a step 81 to which the inner periphery (or outer periphery) of a seal tube 5 is inserted. In such a connection structure, a molten solder 14 is sunk around the end surface and the inner periphery (or outer periphery) or the seal tube 5, by a capillary phenomenon, so that a broad soldering area and a good connection can be obtained. Moreover, by placing foil-form solders 15 and 16 beforehand between the seal tube 5 and the step 81 and then melting them, a more secure soldering can be acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a technique for joining ceramics and metal, and particularly to an improvement in the sealing structure of an electron tube using ceramics.

[Background of the invention]

Among electron tubes, there are a wide variety of electron tubes that use ceramics as a sealing member, such as magnetrons, X-ray tubes, and transmission tubes. Most of them use alumina as the ceramic, and the method of joining with metal members is to attach Mo-
A bonding layer is provided by the so-called high-melting point metal method, in which Mn paste is applied, fired in a hydrogen furnace, a metallized layer is formed, and Ni plating is applied, and a silver-copper eutectic solder is used as a brazing material to produce metal parts. The method of joining with is widely used.

As a specific example, an example of joining ceramics and a metal member will be explained using a magnetron as an example. FIG. 1 shows a cross section of a tube body of a magnetron used in a microwave oven or the like. 1 is a cathode that emits thermoelectrons, 2 is an anode that forms a cavity resonator inside, and a magnetic pole 3 that concentrates magnetic lines of force from outside the tube body into the action space formed by the cathode 1 and the anode 2; 4, and seal cylinders 5 and 6 are abutted against the cylindrical portion of the anode 2 in a manner that encompasses these cylinders. Further, ceramics as a sealing member holds the cathode 1 and includes a cathode terminal 7 for supplying cathode current, a stem ceramics 8 joined to the seal cylinder 5, and an antenna 9 extending from a specific vane of the anode 2.
There is an antenna ceramic 12 that surrounds the seal cylinder 6 and the exhaust pipe support 11 that holds the exhaust pipe 10, and that serves as a radiation window for the generated microwaves.

Here, regarding the joints between the stem ceramics 8, the antenna ceramics 12, and the metal members, the stem ceramics 8 and the seal cylinder 5, the antenna ceramics 12, the seal cylinder 6, and the exhaust pipe support 11 have the same joint structure.

That is, as an example, as shown in FIG. 2, which is an enlarged cross-sectional view of the joint between the stem ceramics 8 and the seal cylinder 5, the end face of the stem ceramics 8 is coated with a metallized film 8a formed by a refractory metal method and a Ni plating layer 8b. The seal cylinder 5 is brazed with silver solder 13. This structure is called a butt joint, and the flexibility of the seal cylinder 5 absorbs the stress caused by the difference in thermal expansion between the seal cylinder 5 and the stem ceramics 8. This structure is a technique also disclosed in Japanese Patent Laid-Open No. 56-24733. This technology allows the use of inexpensive iron material as the seal cylinder. On the other hand, the bonding structure between the stem ceramics 8 and the cathode terminal 7 is as follows.

This is called surface bonding, and as shown in the enlarged view of FIG.
a, Ni plating layer 8b is brazed with silver solder 13 interposed therebetween. In this case, the material of the terminal 7 is a metal having a coefficient of thermal expansion close to that of the stem ceramics 8, for example, if the ceramic is alumina, it is limited to Kovar, Furni, etc.

The metallization technology and bonding structure using the above-mentioned high-melting-point metal method are widely used because silver solder has very good wettability with metal, resulting in good bonding.
On the other hand, the high melting point metal method requires a long process to form a metallized film, which leads to high costs for ceramic members, and is a major obstacle to obtaining cheaper electron tubes.

[Purpose of the invention]

An object of the present invention is to utilize a simple bonding method in order to obtain an inexpensive electron tube, and to provide a bonding structure suitable for using the bonding method.

[Summary of the invention]

It is not necessary to produce a metallized film on ceramics, but instead uses a brazing filler metal to which an active metal is added, and utilizes the shape of the ceramic that is convenient for using this brazing filler metal.

[Embodiments of the invention]

The present invention is applicable to Japanese Patent Application Laid-open Nos. 59-232692 and 60-60.
40687, etc., brazing using a brazing filler metal in which an active metal such as Ti or Zr is added to a silver solder or a copper solder is utilized.

The bonding mechanism of this method is that Ti and Zr in the solder are partially oxidized and react directly with alumina, or that Ti and Zr
ions diffuse into the alumina crystal, forming a solid solution or compound with alumina at the bonding interface, resulting in bonding.

According to this method, brazing can be performed in one heating process by simply supplying the filler metal, and there is no need to go through the complicated process of refractory metal method to obtain a metallized surface, so it is very cost-effective. It is clear that this is an advantageous method.

However, if the joint structure shown in Fig. 2, which alleviates the thermal stress at the joint, is adopted as is, there is no metallized surface on the end of the ceramic that allows the solder to flow well, so when the solder melts, the molten filler metal flows into the sealing cylinder 5. The ceramic side gets wet more and it is difficult to flow to the ceramic side, so a good joint cannot be obtained.

Therefore, as shown in FIG. 4, the present invention is characterized in that the stem ceramics 8 is provided with a stepped portion 81 into which the inner periphery (or the outer periphery) of the seal cylinder 5 fits. According to this joint shape, the melted brazing filler metal 14 enters through the flat surface of the end of the seal cylinder 5 and the inner circumferential surface (or the outer circumferential surface) by capillary action, so that wide brazing can be achieved with a good surface. A bond is obtained.

In addition, in order to make better use of the shape of the ceramic according to the present invention, a foil-shaped brazing filler metal 15 is used as shown in FIGS. 5 and 6.
．． 16 is sandwiched between the seal cylinder 5 and the foil-shaped brazing material in advance to melt the brazing material, thereby achieving more reliable brazing.

〔Effect of the invention〕

According to the present invention, since it is possible to perform brazing by an active metal method that does not require providing an expensive metallized surface on ceramics, it is possible to obtain an inexpensive electron tube. (2) The positioning of the ceramic and the sealing cylinder is automatically achieved by fitting the stepped part provided on the ceramic, so it is possible to have a significantly simpler structure or to eliminate the need for a jig. It has the following effects.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an example of the structure of a general magnetron tube body, Figs. 2 and 3 are sectional views of main parts showing a conventionally popular joint structure of a ceramic and metal cylinder, and Fig. 4.5. 6
The figure is a sectional view of a main part showing the structure of a joint between a ceramic and a metal cylinder according to the present invention. DESCRIPTION OF SYMBOLS 1... Cathode, 2... Anode, 5, 6... Seal cylinder, 7... Terminal, 8... Stem ceramics, 12...
... Ceramics, 13,14°15.16... Brazing metal.

Claims (1)

[Claims] 1. In a joining structure by brazing a ceramic and a metal cylinder, the ceramic has a stepped portion that fits with the inner periphery or outer periphery of the end of the metal cylinder, and the solder contains an active metal. A joining structure of ceramics and metal, characterized in that the metal cylinder is joined by brazing with a material. 2. The ceramic-metal bonding structure according to claim 1, wherein a foil-shaped brazing material is sandwiched between the fitting stepped portion and the metal tube for brazing.