JPS5846548A - Manufacture of cathode structural body for magnetron - Google Patents

Abstract

PURPOSE:To eliminate the necessity for a binding agent and solvent and prevent generation of unevenness in a characteristic due to an excessive or short amount of a solder material, by providing annular hollowed grooves in an inner surface of end hats, composing an annular compression sintered body from a mixture of molybdenum powder and ruthenium powder, filling the sintered body under pressure as the solder material into the hollowed groove and thermally melting the solder material after temporary assembly of an electrode. CONSTITUTION:The second lead wire 4 is extended through without being contacted to the first end hat 2 and cathode main unit 3, and the second end hat 5 is secured to the top part of the second lead wire 4. The cathode main unit 3 is constituted by a spirally formed thorium tungsten wire, and the first and second lead wires 1, 4 are made of molybdenum. The first and second end hats 2, 5 are constituted by a compression sintered body of molybdenum powder, and ring-shaped hollowed grooves 7, 8 are provided respectively in faces of the end hats at a face-to-face position to each other, then ring-shaped solder materials 9, 10 are filled under pressure in the hollowed grooves 7, 8. The solder materials 9, 10 are constituted by a compression sintered body of mixture in proportion about 3:2 by weight of the molybdenum powder and ruthenium powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a cathode assembly for a magnetron, particularly a cathode assembly comprising a spiral cathode body made of thorium tungsten and a cathode support supporting the cathode body.

Generally, the cathode structure of a directly heated magnetron used in a microwave oven or the like consists of a spiral cathode body made of thorium tungsten and a cathode support that supports the cathode body. The cathode support includes a first lead wire, an annular first end hat provided at the top of the lead wire, and a second end hat that passes through the end hat without contacting the first lead wire.
the second lead wire facing the first end hat.
and a second end hat provided on the top of the lead wire, and both ends of the cathode body are soldered to the first and second end hats. - During magnetron operation, the cathode body reaches a high temperature of about 1800°C in the middle, so the first and second lead wires and the first and second end hats are made of high melting point metal such as molyy or butene. used. Further, a high melting point brazing material made of platinum or a platinum-rhodium alloy is used to solder the first and second end hats to the cathode body.

However, since platinum and platinum-rhodium alloys are very expensive, attempts have been made to use a mixture of ruthenium powder and molybdenum powder as the high melting point brazing material. In this case, the mixture is dispersed in a binder liquid containing tld'nitrose, Lurose and acetone and applied to the parts to be soldered. However, since the mixture in the binder liquid tends to precipitate, it is difficult to correctly supply a predetermined amount to the part to be soldered. Causes variation. Furthermore, binder tends to remain in the soldered parts, and if this is gasified and discharged during the exhaust process inside the magnetron tube, the exhaust efficiency will decrease.

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional art.Next, a method of manufacturing a cathode assembly for a magnetron according to the present invention will be described with reference to embodiments shown in the drawings.

In FIG. 1, the first end 2 fixed to the top of the first lead wire 1 is formed in an annular shape.
A second lead wire 4, which passes through the first wire notch 2 and the cathode body 3 without contact, has a second lead wire 4 fixed to the top thereof. The cathode body 3 is made of a spirally formed thorium tungsten wire, and the first and second lead wires 1 and 4 are made of molybdenum.

6 indicates a stem insulator made of ceramic.

The first and second end hats 2 and 6 are made of a compressed sintered body of molybdenum powder, and have grooves 7 and 8 in the shape of grooves on opposing surfaces (inner surfaces), respectively. Ring-shaped solder materials 9 and 10 are press-fitted into the holes. However, the solder material 9
, 10 is a compressed sintered body of a mixture of molybdenum powder and ruthenium powder in a weight ratio of approximately 3:2, and has a dimensional relationship with the end hat as shown in FIG.

After temporarily assembling the electrode members as shown in FIG.
, 1o in vacuum or in a reducing gas atmosphere by high frequency heating, electron beam heating, laser beam heating, etc., the molten solder material covers the end of the cathode body 3 as shown at 10' in FIG. , a predetermined solder bond is achieved.

As described above, according to the method for manufacturing a cathode structure of the present invention, the inner surface of the end hat made of a compressed sintered body of molybdenum powder is provided with a ring-shaped groove, and the ring-shaped groove made of a mixture of molybdenum powder and ruthenium powder is formed. A compressed sintered body is pressed into the groove as a solder material, and after temporary assembly of the electrode, the solder material is heated and melted to braze the end of the cathode body to the end hat. It becomes possible to automatically press fit a suitable solder material into the end hat located at the end hat, and the troublesome work of supplying the solder material to the inner surface of the end hat when assembling the electrode becomes unnecessary. Not only is the solder material inexpensive, but depending on the shape and position of the groove,
It is economical because it allows the amount of solder material to be set to the minimum required amount.
Furthermore, there is no need for binders or solvents, and it is possible to always accurately braze a predetermined amount of solder material at a predetermined position, thereby preventing variations in properties due to excess or deficiency of solder material.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a cathode assembly manufactured by the manufacturing method of the present invention before soldering, FIG. 2 is a side sectional view illustrating the dimensional relationship between the end hat and the solder material of the same cathode assembly, and FIG.
The figure is a side sectional view of the main parts of the cathode structure after soldering. 1.4e...Lead wire, 2,5...e...End, 3...Cathode body, 7,8...
... Concave groove, 9゜'''110 ... Brazing material. Fig. 1 vA2r; a ass

Claims (1)

[Claims] A ring-shaped compressed sintered body made of a mixture of molybdenum powder and ruthenium powder is press-fitted as a solder material into a ring-shaped groove formed on the inner surface of the Entonot made of compressed sintered body of molybdenum powder. 1. A method for producing a cathode assembly for a magnetron, comprising: heating and melting a highly solder material after temporarily assembling the electrode, and brazing the end of the cathode body to the end hat.