JPS6228041Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an elastic holding device for a thermionic emission cathode in an electron gun or the like.

In recent years, chips of rare earth borides, especially lanthanum hexaboride, have been used for the cathodes of electron guns used in electron beam exposure devices or electron microscopes, and as heating means for these chips, a pair of pyrolytic graphite or polymer Generally, the structure is such that the cathode chip is sandwiched between a pair of conductive members made of oriented carbon material on both sides thereof.

(Prior art and its drawbacks) To obtain a stable high-intensity electron beam,
Electrical and mechanical contact between the cathode chip and the heating means and conductive pillars must be maintained stably even at high temperatures of 1500 to 1600 DEG C., which is the working temperature of this type of cathode.

For this reason, it has been proposed to fix an elastic body such as an arcuate leaf spring to the outside of the conductive column in order to absorb the deformation of the holding member that inevitably occurs due to heat generation. (For example, JP-A-51-45640 (No. 2)
(Fig. 3), JP-A-52-77661, Fig. 6) However, in this structure, the middle part of the spring is fixed and both ends are the points of force application, so when the spring is heated, the end part is pushed. It is practically impossible to adjust the pressure appropriately, and there is a drawback that there is a large deviation in the position of the contact point during heating and when not in use.

Furthermore, apart from this, conductive support members 3a, 4a as shown in FIG.
A heat-resistant elastic plate 5 is attached to both outside sides of the
A structure in which the conductive support members 3a and 4a are pressed at the middle has been proposed, but since the conductive support members 3a and 4a are each deformed inwardly into an arched shape, the parallelism with the heat generating member is difficult. There was a drawback that the contact resistance could not be maintained and the contact resistance changed.

Furthermore, in order to improve this problem, a structure as shown in FIG. 2 was proposed, but in this structure, the tips of the auxiliary columns 3, 4 and the elastic plate 5 are close to the Wehnelt electrode 7, so discharge is likely to occur. A new drawback has arisen: the wires have become longer and are more likely to break.

(Purpose) The present invention solves the above-mentioned drawbacks of the conventional device, and obtains a stable electron beam by reducing resistance changes in the current path passing through the cathode chip even under high temperatures. The object of the present invention is to provide a new hot cathode holding device that allows easy adjustment of the temperature and also allows for the spatial position adjustment of the chip.

(Structure) The structure of the proposed device consists of the bases of a pair of conductive pillars that sandwich the emitter tip and the heating element, and the bases of heat-resistant leaf springs (flat plate elastic materials) with bendable tips arranged in parallel on the outside of these pillars. is separately fixed to the inner base of a fixed support vertically disposed on the substrate, and an adjustment screw is screwed through the extension of the fixed support, and the pressure force at the tip of the flat elastic member is adjusted by the adjustment screw. It is designed to be adjusted.

An embodiment of the present invention will be described below with reference to FIG.

Reference numeral 10 denotes an insulating substrate, which is equipped with a conductive terminal, and has a pair of fixed supports 11 vertically disposed thereon.

Reference numeral 12 denotes a conductive column, and a base 13 is fixed to the base inner side 11a of the fixed column by spot welding or other fixing means, and is provided in parallel to the fixed column.

Reference numeral 14 denotes the distal head portion thereof, which holds the emitter tip 1 via the heat-generating holding members 2a and 2b.

Reference numeral 15 denotes a flat elastic plate made of a heat-resistant metal with a high melting point, which is arranged parallel to the outside of the conductive column 12 at a distance d, and its base 16 is connected to the inner step 1 of the fixed column.
1b, and the tip portion 17 is bent 17a at a predetermined angle θ so as to contact the outer surface of the head 14 of the conductive column.

The tip abutting surface 18 of the flat elastic material is tapered according to the bending angle θ so as to maintain surface contact with the outer surface of the head, and the flat elastic material has a flat portion 19 in the middle thereof. , fixed column extension 11c
It is constantly pressed by an adjustment screw 20 that passes through and is screwed into the screw.

(Operations and Effects) In the device of the present invention, the intermediate portion 19 of the flat elastic member 15 is pressed by the adjustment screw 20, thereby producing a pressing force on the tip abutting surface 18.

In this case, the middle part of the flat elastic material is curved inward, which makes the angle θ of the bent part larger, but on the other hand, the flat part (from the base fixed part to the bent part)
Since the straight line distance becomes shorter, there is less change in the position of the tip abutting surface 18 as a whole.

In addition, even if stress is generated near the chip due to thermal expansion during use, the contact surface on the outside of the head of the conductive column is in surface contact and is located at a position that resists the stress, so the partial pressure of the pressing force is even and the chip is clamped. This makes it possible to reduce changes in force.

The holding device of the present invention can stably maintain the contact surface of the chip and the contact pressure because the change in the position of the pressing force application point of the flat plate elastic material, that is, the contact surface 18 is small.

Further, since the pair of adjustment screws 20 can be used to adjust the pressing force against the conductive columns on each side, the position of the electron beam spot can also be adjusted.

[Brief explanation of the drawing]

1 and 2 are sectional views of the main parts of the conventional device, and FIG. 3 is a front view of the main parts of the present device.

Claims (1)

[Scope of utility model registration request] In a hot cathode device in which a cathode chip is held under pressure by a pair of heating elements, and the heating elements are supported by a pair of conductive columns, the conductive columns have their bases suspended above an insulating base. A heat-resistant metallic flat plate elastic member is fixed to the inside of the fixed column, has a base fixed to the inside of the stepped portion of the fixed column, and is arranged parallel to the conductive column at a constant distance from the outside of the conductive column. The portion is bent so as to come into surface contact with the outside of the head of the conductive column, and the intermediate flat portion thereof is configured to be pressed by an adjustment screw threaded through the extension portion of the fixed column. Hot cathode holding device.