JPH04322029A - Impregnated type cathode and manufacture thereof - Google Patents

Abstract

PURPOSE:To achieve uniform fixation and provide a uniform temperature at a surface of a cathode by brazing a cathode pellet and a cathode sleeve to each other via a metal material having a high melting point deposited on the back surface and side surface of the cathode pellet. CONSTITUTION:A metal material having a high melting point is deposited on the back surface and side surface of a cathode base by a sputtering method, thus obtaining a coated layer 3. A blazing material 4 is applied onto the coated layer 3 deposited on a cathode pellet 1, to be engaged with a cathode sleeve 2, followed by brazing. Because the surface of the coated layer 3 becomes wet when the blazing material 4 applied onto the back surface of the pellet 1 is molten, it is completely coated with the blazing material. After fixing of the cathode base to the cathode sleeve 2, an electron radioactive material is applied to the surface of the cathode base, followed by a heat treatment in a hydrogen furnace. Consequently, the electron radioactive material is impregnated in pores of the pellet 1, and the residual electron radioactive material is removed, thus producing the pellet 1. Furthermore, since the pellet 1 and the sleeve 2 are brazed to each other, it is possible to achieve uniform fixation, enhance thermal conduction, provide a uniform temperature at the whole surface of a cathode, and enhance an electric characteristic.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impregnated cathode used in cathode ray tubes, microwave tubes, etc., and a method for manufacturing the same.

0002

BACKGROUND OF THE INVENTION Hitherto, impregnated cathodes have been used for cathodes used in magnetrons, which are subjected to strong electron reverse impact and ion impact, and cathode ray tubes, which are subject to harsh usage conditions. An example of the structure of this conventional impregnated cathode is as shown in FIG. That is, in the same figure, 1 is a cathode pellet, which is made of a mixture of barium oxide, calcium oxide, aluminum oxide, etc., and is attached to a cathode base formed into a predetermined shape by sintering high-melting point metal powder mainly composed of tungsten powder. It is formed by melting and impregnating an electron radioactive material. A cathode sleeve 2 supports and fixes the cathode pellet 1 and houses a heater 5 therein, and is made of thallium or the like, which can withstand high temperatures during use and is easy to weld. 6 is a cap made of a high-melting point metal plate such as molybdenum, which is used to connect the cathode pellet 1 and the cathode sleeve 2.
The cathode pellet 1 and the cathode sleeve 2 are fixed by welding.

[0003] This cap 6 is interposed to prevent electron radioactive material from scattering from the back surface of the cathode pellet 1 to the heater side. In other words, the electron radioactive material leaks out from the entire surrounding area of the cathode pellet 1, and when the electron radioactive material scatters to the heater 5 side, the electrical insulation between the cathode pellet 1 and the heater 5 decreases, causing characteristic deterioration, and the electron radioactive material This is because the amount of carbon dioxide decreases and the lifespan is shortened.

In order to prevent this electron radioactive material from scattering, the cap 6 is not used, and the back and side surfaces of the cathode pellet 1 are coated with a brazing material to fill the voids on the surface (made by sintering high melting point metal powder). A method has also been considered in which the cathode sleeve 2 is directly brazed using the brazing material while sealing the gap (gap portion). In this case, since the brazing temperature is very high (approximately 2000° C.), the electron emissive material is impregnated into the porosity of the cathode base after brazing the cathode sleeve to prevent the electron emissive material from deteriorating.

[0005]

[Problems to be Solved by the Invention] However, in the conventional method of fixing the cathode pellet 1 and the cathode sleeve 2 through the cap 6 by welding, welding is difficult because these materials are both high-melting point metals. This could not be done reliably, the cathode temperature would vary depending on the position of the cathode pellet, and the cathode pellet 1 would peel off from the cathode sleeve 2 during operation, causing problems in terms of electrical characteristics and reliability. Furthermore, the conditions for the welding work itself were severe and work efficiency was extremely low.

On the other hand, in the conventional brazing method, a brazing material with good solder flow (for example, Mo-Ru or Mo-N) is used.
i), the brazing material flows into the pores of the cathode substrate, significantly reducing the amount of electron radioactive substance impregnated into the cathode pellet 1, and significantly shortening the service life. When using (for example, Mo2B), countless pinholes are formed on the surface of the brazing material after brazing, and the shielding effect cannot be achieved, so it has not been put to practical use.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention aims to connect a cathode pellet and a cathode sleeve by brazing through an adhesion layer of a high melting point metal material formed on the back and side surfaces of the cathode pellet. It's because it's stuck.

Another means of the present invention is to set an appropriate thickness of the adhesion layer according to the porosity of the cathode substrate. Specifically, when the porosity is 18 to 20%, the adhesion layer is Layer thickness 5~
When the porosity is 20 to 25%, the thickness of the adhered layer is set to 7 to 10 μm.

Still another means of the present invention includes a step of forming a cathode substrate, a step of forming an adhesion layer of a high melting point metal material on the back and side surfaces of the cathode substrate, and brazing the cathode pellet and the cathode sleeve. The purpose of the present invention is to manufacture an impregnated cathode by combining a step of impregnating an electron emitting substance, a step of impregnating an electron emitting substance, and a step of disposing a heater.

0010

[Function] According to the present invention, since the cathode pellet and the cathode sleeve are fixed by brazing through the adhesion layer of a high-melting point metal material, the adhesion layer acts as a barrier and pores in the cathode base. In addition, the cathode pellets and the cathode sleeve can be firmly and uniformly fixed without the brazing material flowing into the cathode sleeve. Furthermore, there is no risk of wax flowing into the pores of the cathode substrate.
A brazing material with good solder flow can be used, no pinholes are generated in the brazing material after brazing, and the brazing material acts as a complete barrier, completely preventing scattering of electron radioactive substances.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a cross-sectional view of an impregnated cathode according to an embodiment of the present invention. In the figure, 3 is an adhesion layer of a high melting point metal material such as tungsten, molybdenum, iridium, or rhenium, 4 is a brazing material such as a molybdenum-ruthenium alloy, and other symbols are the same as in FIG. 3. .

[0012] To explain the manufacturing method of this impregnated cathode, first, a high melting point metal powder mainly composed of tungsten powder with a particle size of 2 to 10 μm is press-molded, and a cathode substrate is formed into a cathode pellet shape in a reducing atmosphere. Form. The cathode substrate can be formed by press-molding it into the shape of a cathode pellet in advance and sintering it, but if exact dimensions and shape are required, oxygen-free copper or plastic can be used to form a press-formed body of any shape. It may also be formed by impregnating it, machining it into the shape of a cathode pellet, and then removing the oxygen-free copper or plastic in a vacuum furnace or the like.

A high-melting point metal material such as tungsten, molybdenum, iridium, or rhenium is deposited on the back and side surfaces of the cathode substrate by sputtering or CVD to form a deposition layer 3. An example of a sputtering method for forming this adhesion layer 3 will be explained with reference to FIG.

In FIG. 2, 7 is a cathode substrate whose surface (
The electron emitting surface of the cathode pellet is fixed in contact with a jig 8, and the jig 8 is connected to a positive electrode 9. The other negative electrode 10 supports a target 11, and in this embodiment, tungsten material is used as the target. 12 is an inert gas atmosphere such as argon, and 13 is a power source for applying a high frequency voltage. When a high frequency and high voltage is applied by this device, the argon gas is ionized into positive ions Ar+ with extremely high energy, which jump into the negative side of the electrode, that is, the tungsten of the target 11.
Tungsten gains the high energy of Ar+ and flies out, and adheres to the exposed surface of the cathode substrate 7 (that is, the back and side surfaces of the cathode pellet). The thickness of the deposited layer is approximately proportional to the high voltage application time and can be freely adjusted.

Since the tungsten ejected from the target 11 becomes fine particles and reaches the anode side and adheres to the exposed surface of the cathode substrate 7, the larger the exposed area of the pores in the cathode substrate 7, the more completely the pores are completely covered. Requires a thick adhesion layer to provide protection. The ratio of the exposed area of the pores is approximately proportional to the porosity (the ratio of the volume of the entire cathode substrate to the volume of the pores of the entire cathode substrate), and as a result of experiments, it was found that a cathode substrate with a porosity of 18 to 20% On the other hand, the coating thickness is 5 to 7 μm and the porosity is 2.
It has been found that in the case of 0 to 25%, a coating thickness of 7 to 10 .mu.m can sufficiently prevent the intrusion of the brazing material.

When forming an adhesion layer by the CVD method, the cathode is formed by disposing a cathode substrate in a reaction tube and thermally decomposing it by introducing tungsten tetrafluoride gas, as in the usual CVD method. A tungsten material can be deposited on the exposed portion of the substrate to form a deposited layer.

A molybdenum-ruthenium alloy brazing material is applied onto the adhesion layer of the cathode pellets 7 on which the adhesion layer 3 has been formed, and a cathode sleeve 2 made of a molybdenum-rhenium alloy is fitted and brazed in a hydrogen furnace. I do. During this brazing, the back surface of the cathode pellet 7 is not in contact with the cathode sleeve 2, but the attached brazing material is once melted and the adhesion layer 3
Since the surface of the solder is wetted, the back side is also completely covered with wax. A suitable material for the cathode sleeve is a heat-resistant molybdenum-rhenium alloy that does not require welding and has good solder flow.

After the cathode base 7 and the cathode sleeve 2 are fixed together, an electron radioactive material containing a mixture of barium oxide, calcium oxide, aluminum oxide, etc. in a predetermined ratio is coated on the surface of the cathode base 7, and heat-treated in a hydrogen furnace or the like to form a cathode. The cathode pellet 1 is formed by impregnating the pores of the pellet with an electron radioactive substance and removing the excess electron radioactive substance remaining on the surface.

A cathode portion can be formed by placing a heater 5 insulated with alumina or the like inside the cathode pellet 1 and cathode sleeve 2 fixed together, and fixing it at a predetermined position within the electron tube by welding or the like. .

[0020]

[Effects of the Invention] According to the present invention, since the cathode pellet and the cathode sleeve are fixed by brazing, they can be fixed uniformly, heat conduction is improved, the entire cathode surface has a uniform temperature, and electrical characteristics are also improved. . Moreover, the brazing work is easy and a large amount of brazing can be performed at one time, and work efficiency is greatly improved compared to conventional welding, and it can be manufactured at a low cost.

On the other hand, since an adhesion layer made of a high melting point metal material is formed on the back and side surfaces of the cathode substrate, there is no penetration of the brazing material into the pores of the cathode substrate, and the amount of the electron radioactive substance impregnated is small. It is not inferior to conventional caps, and has the effect of significantly improving lifespan and reliability due to improved fixation strength. Furthermore, since the surface of the adhesion layer is coated with a dense brazing material, it is possible to completely prevent electron radioactive substances from scattering toward the heater side, and there is no deterioration in the insulation between the cathode heaters.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an impregnated cathode that is an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a sputtering apparatus that is a step example of the present invention.

FIG. 3 is a longitudinal cross-sectional view of an example of a conventional impregnated cathode.

[Explanation of symbols]

1 Cathode pellet 2 Cathode sleeve 3 Adhesive layer 4. Waxing material 5 Heater 7 Cathode substrate 8 Jig 9 Positive electrode 10 Negative electrode 11 Target 12 Argon gas atmosphere 13 Power supply

Claims (4)

[Claims] Claim 1: A cathode pellet in which a cathode substrate made of a sintered high-melting point metal porous body containing high-melting point metal powder as a main component is impregnated with an electron-emitting substance containing barium as a main component, and the cathode pellet is supported. An impregnated cathode comprising a cathode sleeve that is fixed and has a heater housed therein, and a heater disposed inside the cathode sleeve,
An impregnated cathode in which the cathode pellet and the cathode sleeve are fixed to each other by brazing through an adhesion layer of a high melting point metal material applied to the back and side surfaces of the cathode pellet. 2. The impregnated cathode according to claim 1, comprising:
An impregnated cathode, wherein the high melting point metal porous body has a porosity of 18 to 20%, and the adhered layer has a thickness of 5 to 7 μm. 3. The impregnated cathode according to claim 1,
An impregnated cathode, wherein the high melting point metal porous body has a porosity of 20 to 25%, and the adhered layer has a thickness of 7 to 10 μm. 4. A step of forming a cathode substrate by sintering a powder mainly composed of a high-melting point metal powder, a step of depositing a high-melting point metal material on the back and side surfaces of the cathode substrate, and A method for producing an impregnated cathode comprising the following steps: brazing a cathode sleeve and a cathode sleeve; impregnating the cathode base with an electron radioactive substance; and arranging a heater within the cathode sleeve.