JPH103846A - Manufacture of impregnated negative electrode for cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability with reproducibility, to secure the positioning of a positive electrode in a support part, and to aim at economical production by inserting a pure metal material between an emission positive electrode and a support part so as to facilitate the soldering. SOLUTION: A metallic transporting material 8, which is chemically neutral and with which soldering of both an emission positive electrode and a support part can be performed at a sufficiently low temperature so as to prevent the deterioration of the emission characteristic of the positive electrode, is inserted between the emission positive electrode 1 and the support part 13. A selected material has a melting point between the operating temperature of a negative electrode and the operating temperature of the metal which forms the positive electrode. The material 8 provided as a boundary between the positive electrode 1 and the support part 13 is formed into the form of a metal powder, a ribbon or a wire. Especially, the material 8 is directly coated by vacuum evaporation on the support part 13 so as to restrict the quantity of the material 8 at the minimum so as to lower the weight and dimension of the negative electrode in view of heat output. Thermal output characteristic of the negative electrode is not influenced by the thickness of the material 8, and the thickness is set at a value, which can obtain the excellent soldering characteristic between the positive electrode 1 and the support part 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an impregnated cathode, and more particularly to a method for mounting an electron gun on a cathode ray tube.

[0002]

BACKGROUND OF THE INVENTION Impregnated cathodes include a porous emission anode made of a refractory material (tungsten, molybdenum, rhenium, etc.) impregnated with an emission material (barium, strontium, calcium, aluminum, cesium, etc.).
The anode is placed on a support, typically in the form of a small heat-resistant metal dish (tantalum, molybdenum, etc.). The anode and dish unit forms the top of the cathode.

[0003] The emitting anode and its support are assembled to form a mechanical unit that can withstand the various stages of cathode manufacture and the high operating temperatures of the cathode ray tube. Furthermore, the contact between the anode and its support should be as good as possible to guarantee the performance of the cathode. Conventionally,
Various methods have been used to create the top of the impregnated cathode. One method is to deposit a coating on the back surface of the emission anode to facilitate soldering to the support. The coating is generally based on molybdenum and rhenium powder. The main disadvantages of the above method are that the coating is expensive, difficult to contain due to the high degree of evaporation and deposition, and difficult to control and reproduce the amount deposited on the support. That the thickness of the anode is liable to change, that the coating on the cathode having a small size (less than 2 mm) is impossible, and that the surface of the anode covered with the coating needs to be adjusted in order to perform welding. It is.

[0004] US Patent No. 5,211, issued June 6, 1993 to LR Falce et al.
A second method described in U.S. Pat. No. 8,263 is to plug the emission anode of the cathode on the support with a lid or a piece that partially covers the support. The lid has an opening to allow the anode to discharge into the tube. The lid is soldered to the support and forms a single piece with the top of the cathode. The main disadvantages of the above method are that the weight of the cathode increases when creating the above structure and is detrimental to the activation time of the cathode, and the low thermal conductivity between the anode and the rest of the cathode reduces the overall The risk of assembling the anode obliquely or with a high degree of freedom, the presence of metal fragments between the gun electrode in front of the cathode and the surface of the anode, Deforming the structure of the applied electric field and subsequently depositing material on the surface of the anode at the exit of the cathode, reducing the output from the cathode.

[0005] US Pat. No. 5,171,1 issued to KS Lee on December 15, 1992
No. 80 discloses a third method of assembling the anode directly on its support without soldering, and then forming the bond by removing the emissions contained in the anode. Processing the assembly of parts in a high temperature hydrogen furnace to cause a chemical reaction with the support. The main drawbacks of the above method are that the emission material contained in the anode is lost so that a bond with the support can be formed, shortening the service life of the cathode, a large number of small dimensions for processing in a hydrogen furnace That only a pile of parts are required, that the exact positioning of the anode is not guaranteed by the movements that occur during processing in the furnace or during chemical reactions, and that the positioning stability is in use. Is not guaranteed for the positive electrode, and the product may be exfoliated.

[0006] On July 2, 1992, J. Choi
A fourth method, disclosed in US Pat. No. 5,128,584, issued to Choi), uses a preliminary treatment to roughen both surfaces to be joined, with the cathode anode being directly connected to the support. To be soldered. Soldering is done by electrical resistance and is easily done by forming a good contact between both components. The biggest drawback of the above method is that the power required to solder the refractory material causes a significant temperature rise that partially modifies or destroys the emissions contained in the anode, assembling the cathode into the electron gun At this time, the solder is weak because it remains weak and brittle, it is necessary to adjust the surface of the anode which is roughened to form the solder, and the surface of the anode having a small size (less than 2 mm) Is difficult to adjust.

[0007]

Accordingly, a method for producing an impregnated cathode, and more particularly, the disadvantages of the prior art described above, have been solved, and a highly reliable and reproducible positioning of the anode on the support is provided. A method is required to assemble the emitting anode to the support that is easy to implement and economical, while at the same time ensuring a positive effect on the emissivity of the anode.

[0008]

SUMMARY OF THE INVENTION A method of manufacturing an impregnated cathode according to the present invention comprises the steps of soldering a porous emission anode made of a refractory material inside a support made of a refractory material. Pure metal material is provided between the emitting anode and its support for easy attachment.
In particular, in an advantageous embodiment of the invention, the transport material is a thin metal tab provided between the emitting anode and its support.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, an impregnated cathode generally comprises a cylindrical body 2, the end of which is the top of the cathode constituting the emission anode 1. . In many cases, the emission anode 1 is provided on a support 13 which is mostly made of tantalum or molybdenum and contains tungsten as a basic material. The heating element 5 is inserted inside the main body 2. The cylindrical portion 4 forms an outer skirt portion of the cathode and functions as a thermal protection portion for preventing a loss of heat generated by the heating element 5 in order to increase a thermal efficiency of the assembly. The cathode body 2 is for example soldered to the body 2 at a position 6 as shown in FIG. 2 and maintained in a position inside the protective part by a strip 3 soldered to an outer skirt 4. You.

One of the difficult problems associated with the assembly of the various components of the cathode is the connection of the anode 1 to its support 13.
This connection is required to be mechanically strong at high operating temperatures above 1200 ° C., to provide good thermal conduction and to be neutral towards the emission characteristics of the anode. The parameters of stability during discharge, duration of use, arc time, and stability of the discharge threshold depend essentially on the mechanical strength of the anode relative to the rest of the cathode structure.

Since the emission anode and its support are made of a heat-resistant material, it is very difficult to make a direct connection between both components by soldering. Many solutions presented in the prior art do not provide a simple, reliable and inexpensive solution with the reproducibility required for mass production of the main components of a cathode ray tube. Destroying the porosity of the anode in order to obtain a good contact between the refractory metal support 13 and the emitting anode 1 which makes it possible to optimize the heat transfer between the heating element 5 and the anode; It is necessary to join the materials by soldering them together without changing the emission characteristics. For this reason, very high temperature soldering is prohibited.

As shown in FIG. 2, the present invention provides a method for chemically neutralizing between the emission anode 1 and its support 13,
It is also proposed to insert a metallic transport material 8 that allows both components to be soldered at a sufficiently low temperature so as not to degrade the emission characteristics of the anode. For this reason, it is necessary that the selected material has a melting point between the operating temperature of the cathode and the operating temperature of the metal forming the anode.

The transport material provided as a boundary between the anode and its support is in the form of a metal powder, a flat ribbon or a wire. According to an advantageous embodiment of the invention, the transport material is, according to an advantageous embodiment of the invention, in particular, because for heat output reasons it is necessary to minimize the amount of transport material in order to reduce the weight and / or size of the cathode. It is directly coated on the support 13 by vacuum evaporation. According to this method, the thickness of the layer of material 8 is preferably controlled between 1 and 25 microns. This thickness is such that good solderability can be obtained between the emission anode 1 and the support 13 without affecting the heat output characteristics of the cathode.

[0014]

According to another preferred embodiment of the present invention, the transport material is in the form of a thin metal tab selected with a thickness in the range of 1 to 25 microns. Advantageously, the tab is cut so as not to occupy the entire contact surface between the support 13 and the anode 1 in order to reduce the weight of the transport material. However, for reliable soldering between the anode and its support, the surface covered with the transport material must be large enough, taking into account the small dimensions of the components to be soldered. is necessary. Experiments have shown that a tab surface area in the range of 0.4 to 0.7 times the surface area of the generally rounded anode surface can assure soldering of components under conditions of excellent reliability. Indicated.

As shown in FIG. 3 showing the inside of the support 13, the tab 10 is advantageous for automatic centering, for example, upon insertion into the generally dish-like support 13. Is a rectangular shape with four rounded corners. According to this method, by placing the soldering point 9 at the center of the anode 1, the soldering of the anode 1 to the support 13 is more reliably performed. In the case of an annular cylindrical emitting anode with a diameter of 1.27 mm, for example, a metal tab with a length of 1.1 mm and a width of 0.6 mm is selected, with a metal thickness selectable between 1 and 25 microns. .

The metal of the boundary material 8 is chosen such that it can guarantee a good mechanical connection between the anode and its support and does not undergo a chemical reaction at high temperatures.
Similarly, its melting point must be low enough not to degrade the emission characteristics of the anode. To realize the present invention, various metals, whether pure or alloyed, are used, and nickel, chromium, vanadium, and rhenium are, for example, neutral from a mechanical point of view and emission characteristics of the emission anode. Excellent results were obtained from both viewpoints.

According to one advantageous embodiment of the present invention, pure nickel is selected to make tab 10. The metal has a cathode operating temperature of around 1200 ° and 3410 °
145 between the melting point of a tungsten anode on the order of C
It has a melting point of 3 ° C. and gives good thermal conductivity and very good solder feasibility with tungsten and tantalum. In addition, nickel is a magnetic material and has the added advantage of allowing for automated coating of the tub dish with an electromagnet that is very difficult to perform manually when considering the small dimensions of the components that make up the cathode. Advantages are obtained.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an impregnated cathode according to the prior art.

FIG. 2 is a side view of the cathode according to the present invention, in which an upper part of the cathode is shown in an exploded view.

FIG. 3 is a plan view of a preferred embodiment of the present invention.

FIG. 4 is a side sectional view of a preferred embodiment of the present invention.

[Description of Signs] 1 Emission anode 2 Cylindrical body 3 Slender piece 4 Cylindrical part 5 Heating element 6 Soldering position 8 Boundary material 9 Soldering point 10 Tab 13 Supporting part

Claims (1)

[Claims] 1. A step of soldering a porous emission anode made of a heat-resistant material to the inside of a heat-resistant metal support. In order to facilitate soldering, a pure metal material is used for the anode and its support. A method for producing an impregnated cathode provided between