JPH05342982A - Impregnated type cathode and its manufacture - Google Patents

Abstract

PURPOSE:To provide an impregnated type cathode capable of obtaining an impregnated type cathode substrate of high productivity and stable quality and also a manufacture of the cathode by facilitating automation of port- processes while preventing wafers from warping. CONSTITUTION:On the whole surface of a porous tungsten thin sheet 11 impregnated with an electron emitting substance 13, a rough surface 14 is made. A solder 12 is applied to the rough surface and sintered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impregnated cathode and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, as a cathode for an electron tube such as a cathode ray tube, there has been an impregnated cathode in which a hole of a porous tungsten thin plate is impregnated with an electron emitting substance (emitter).
This impregnated cathode is used by being incorporated in a cathode structure as shown in FIG. 4, for example. That is, the impregnated cathode substrate 1 in the form of a short cylinder is housed in a cup 2 in the form of a short cylinder with a bottom, and is fixed via the brazing material 3. This cup 2 is inserted into one end opening of a cylindrical sleeve 4 from the bottom side thereof, and is fixed to the sleeve 4 with the impregnated cathode substrate 1 exposed. A heater 5 is built in the sleeve 4. Furthermore, this sleeve 4 has three straps 7
It is coaxially supported and fixed to the central portion of the cylindrical holder 6 via.

Various methods have been already known as a method for producing this type of impregnated cathode, and the following method is shown as one of the methods in JP-A-63-34830. There is. First, the porous tungsten rod is sliced or the tungsten powder is pressed and sintered to obtain a wafer-shaped large-diameter porous tungsten thin plate (hereinafter referred to as wafer) 11 shown in FIG.
A brazing material 12 such as ruthenium, molybdenum paste or the like is applied to one surface of the wafer 11 and sintered, and then an electron emissive material 13 such as BaO, CaO, Al ₂ is applied to the voids.
O ₃ = 4: 1: 1 molar ratio is melted and impregnated from the side opposite to the brazing filler metal 12. Wafer-1 thus obtained
1 is cut out into a predetermined shape by electric discharge machining or laser machining to obtain a chip-shaped impregnated cathode substrate (hereinafter referred to as a chip). After that, if necessary, Ir, Os
And the like, and then incorporated into the cathode structure.

[0004]

In the above disclosed example, the wafer-11 has a thickness of 0.4 to 0.5 mm and a diameter of 30 m.
Although it is about m, it is clear that it is desirable that the diameter is large in order to improve the production efficiency, without needing to give a history of semiconductors and the like.

The wafer 11 of this type is warped as shown in FIG. 5 by heat treatment at about 1950 ° C. after coating the brazing material 12 and heat treatment at about 1400 ° C. at the time of impregnation with the electron emissive material 13. In particular, since the brazing filler metal 12 formed on the one surface side is made of ruthenium molybdenum, which is different from the wafer-11, the compressive stress of the brazing filler metal surface acts due to the high temperature treatment, and the brazing filler metal 12 warps in a convex shape on the brazing filler metal surface side. Inconvenience occurs.

That is, the magnitude of the warp is the thickness of the brazing material 12,
Depending on the heat treatment temperature, time, etc., the greater the amount of these factors, the greater the amount of warpage. Also, the larger the diameter,
It is natural that the warp amount becomes large. If the warp amount becomes large, not only does it hinder the automatic feeding of the wafer 11 in the post-process, but also when the wafer 11 is cut out into a chip shape by laser processing or the like, the wafer 11 is against the laser beam. Vertically set and automatically cropped. At that time, wafer-1
If there is a warp in 1, the focus of the laser beam will be in a defocused state and will not be cut off. Further, even if the laser output is increased and cut, a chip having a predetermined size cannot be obtained because it is cut obliquely or a burr becomes large. This causes inconveniences such as a more complicated automated facility for assembling the cathode assembly.

The present invention has been made in view of the above circumstances, and it is an impregnated cathode capable of preventing warpage of a wafer, facilitating automation of a post-process, and obtaining chips having high mass productivity and stable quality. It is intended to provide a manufacturing method.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides an impregnated cathode in which an unevenness is formed on the back surface of a porous tungsten thin plate impregnated with an electron emitting substance, and a brazing material is applied and sintered on the uneven surface. Is.

Further, the present invention comprises a step of forming an uneven surface on one surface of a large-diameter porous tungsten thin plate having pores,
Next, a step of applying and sintering a brazing material on the irregularities of the porous tungsten thin plate, a step of impregnating the pores of the porous tungsten thin plate with an electron emissive substance, and a step of impregnating the electron emissive substance A method for producing an impregnated cathode, comprising a step of cutting out the impregnated porous tungsten thin plate into a predetermined shape by electrical discharge machining or laser machining to obtain an impregnated cathode substrate.

[0010]

According to the present invention, the warp of the wafer is prevented, the automation of the post-process is facilitated, and the chip having high mass productivity and stable quality can be obtained. That is, as shown in FIG. 2, by forming the unevenness 14 on one surface of the wafer 11 and increasing the roughness, tensile stress is generated on the surface. And
When heat treatment is applied, as is apparent from FIG. 2, warpage occurs due to deformation on the processed side of the unevenness 14 into a concave shape. Further, when the brazing material 12 is applied to one surface of the wafer 11 and melted and baked, a compressive stress is generated on the surface of the application side, and the surface is deformed to be convex and warped. The size of the concave or convex warp is regulated by the surface roughness and the thickness of the brazing material 12 in addition to the heat treatment conditions (temperature and time).
In view of this, in the present invention, a warp-free wafer 11 is formed by imparting tensile stress and compressive stress to one surface of the wafer 11 to cancel the uneven warp, facilitating automation of the post-process and improving mass productivity. It is possible to obtain an impregnated cathode of rich and stable quality.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

The impregnated cathode according to the present invention is constructed as shown in FIG. 1. When the same parts as those in the conventional example (FIG. 5) are designated by the same reference numerals, the holes are impregnated with the electron emissive material 13. Concavities and convexities 14 are formed on the back surface of the wafer 11, that is, on the surface opposite to the electron emission surface.
Is applied and sintered.

Next, a method of manufacturing the impregnated cathode will be described. For example, as disclosed in Japanese Patent Laid-Open No. 63-34830, a tungsten powder having a particle size of 2 to 10 μm is compression molded and then reduced. Sintering in a strong atmosphere to form a large wafer rod having a large diameter of, for example, about 50 mm. Then, in order to improve the workability, the hole portion of the wafer-rod is impregnated with copper, and then the thickness is 0.5 mm and the diameter is 3 by lathe processing or wire electric discharge processing.
Slicing is performed on a wafer of about 0 mm. The surface of the wafer-11 shown in FIG. 2 thus obtained is
Although it depends on the conditions of electric discharge machining, since the roughness is about 10 μm, it is machined to 2-3 μm or less by polishing, lapping or the like. This is for facilitating the removal of the surplus substance after impregnation with the electron emitting substance in the subsequent step and for ensuring the smoothness of the electron emitting surface. In the above steps, there is no distinction between the front and back of the wafer-11.

Next, unevenness 14 having a roughness of 15 to 20 μm is formed on one surface of the wafer 11 by polishing. As a polishing method, a fused alumina-based polishing cloth paper No. 220 was used for polishing while dripping water, followed by washing with water and drying. Etching is also acceptable. It is not necessary to specify the polishing method, and other well-known methods can be used without any problem.

Next, as shown in FIG. 3, 40% of ruthenium and 6 of molybdenum were formed on the unevenness 14 on one surface of the wafer 11.
A brazing material 12 made of a suspension prepared by adding an organic binder to a mixed powder of 0% is applied by a printing method to a thickness of about 50 μm, dried, and then heated to about 1950 ° C. in a reducing atmosphere. , Melt and bind.

Then, in the holes of the wafer-11, Ba is deposited.
An electron emissive substance 13 composed of O, CaO and Al ₂ O ₃ is impregnated, and the surplus substance remaining on the surface is removed to obtain an impregnated wafer-11. Wafer-1 thus completed
No. 1 was offset by the effect of the unevenness 14, and there was almost no warp even by the above heat treatment, and a flat (10 μm or less) wafer-11 could be obtained. On the other hand, in the case of not having the conventional unevenness, as shown in FIG.
A warp of 0.5 mm occurred. Therefore, it is difficult to automate the removal of the surplus electron emissive material (not shown) on the wafer surface, which must be removed by brushing one by one.
This is a labor-intensive task and causes high costs. Then, a laser beam is applied to this wafer 11 to have a diameter of 1.
Cut out into 45 mm chips. Laser beam is wafer
The focus is set to be perpendicular to the plane. At this time, if the wafer 11 is warped, the focal point will not be in focus, so that the laser beam cannot be cut out unless the laser output is increased. Moreover, if the focus is corrected and cut out, not only the equipment becomes extremely complicated and expensive, but also the tip of the tip is inclined so that the tip has a trapezoidal cross section, which is also to be assembled later in the cathode structure. It becomes a factor that makes automation difficult in the process.

The thus-obtained chip shown in FIG. 1 has a metal coat (not shown) such as Ir or Os on the surface.
And is used for assembling the cathode structure as shown in FIG. The cathode structure completed in this way has no difference in appearance from the conventional one, and even if it is used for a color cathode ray tube, no adverse effect on emission characteristics is recognized, and it has the same performance as the conventional product. I was able to confirm that I am doing.

The roughness of the unevenness 14 in the present invention is
The compressive stress changes depending on the application / sintering of the brazing material 12 of the wafer-11 and the impregnation condition of the electron emissive material 13. Therefore, the warp amount changes, so that the tensile stress corresponding to the degree is offset by the roughness. It can be changed to. In order to generate a tensile stress on the coated surface side of the brazing material 12, it is sufficient to perform processing at least rougher than the opposite side surface (side surface impregnated with the electron emissive material 13).
The tensile stress becomes large.

[0019]

According to the present invention, since unevenness is formed on one surface of a wafer impregnated with an electron emissive substance, and a brazing material is applied and sintered on the unevenness, the warp of the wafer is reduced. Or you can prevent it. Therefore, the production of the chip-shaped impregnated cathode substrate becomes extremely easy. Further, the adhesion of the brazing material to the wafer is improved, and the risk of peeling is reduced, which is a great effect. In particular, as the diameter increases, this effect is further increased, which is an indispensable technique.

[Brief description of drawings]

FIG. 1 is a sectional view showing an impregnated cathode according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a method of manufacturing an impregnated cathode according to an embodiment of the present invention.

FIG. 3 is a sectional view showing a method of manufacturing an impregnated cathode according to an embodiment of the present invention.

FIG. 4 is a perspective view showing a cathode structure using an impregnated cathode.

FIG. 5 is a sectional view showing a method of manufacturing a conventional impregnated cathode.

[Explanation of symbols]

11 ... Wafer- (porous tungsten thin plate), 12 ... Wax material, 13 ... Electron emissive material, 14 ... Unevenness.

Claims (2)

[Claims] 1. An impregnated cathode, characterized in that irregularities are formed on the back surface of a porous tungsten thin plate impregnated with an electron emissive substance, and a brazing material is applied and sintered on the irregular surface. 2. A step of concavo-convexing one surface of a large-diameter porous tungsten thin plate having pores, then a step of applying and sintering a brazing material on the concavo-convex of the porous tungsten thin plate, In the step of impregnating the hole portion of the porous tungsten thin plate with an electron emissive substance, then, the porous tungsten thin plate impregnated with the electron emissive substance is formed into a predetermined shape by electrical discharge machining or laser machining. And a step of cutting out to obtain an impregnated-type cathode substrate.