JPH0747781Y2 - Hot cathode holding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a pinching and holding device for a thermionic emission cathode in an electron gun or the like.

[Prior Art] Conventionally, a hot cathode holding device of an electron gun used in an electron beam exposure apparatus, an electron microscope and the like has a structure shown in FIG. 2 and FIG. Incidentally, FIG. 3 shows the structure shown in Japanese Utility Model Publication No. 62-28041.

First, the structure of FIG. 2 will be described. A pair of electrodes 2 to which a heating voltage is applied is implanted on the upper surface of the insulating substrate 1. A large-diameter portion 2b of this electrode 2 is implanted in the insulating substrate 1, and a tip portion of the electrode 2 becomes the small-diameter portion 2a so that it can be inserted into, for example, a socket (not shown) to which a conductor from a power source is connected. . The large-diameter portion 2b of the electrode 2 is provided with a column mounting surface 2c formed so as to be parallel to the side surface,
The mounting portions of the pair of supports 3 are fixed to the column mounting surface 2c with screws 4, respectively. The pillar 3 is a through hole of the insulating substrate 1.
It extends downwardly through 1a, and the opposing surface on the lower end side has a structure in which the cathode chip 6 is sandwiched and held via a pair of heaters 5.

Next, the structure of FIG. 3 will be described. A pair of fixed columns 11 are fixed to the lower surface of the insulating substrate 10.
Conductive columns 12 are fixed to the insides of 11 respectively. The lower end side opposing faces of the conductive columns 12 hold the cathode chip 6 through a pair of heaters 5 as in the case of FIG. .
An elastic plate 13 is fixed to the fixed support column 11 at a constant distance from the outside of the current-carrying support column 12.
Has a structure in which the energizing column 12 is pressed by the adjusting screw 14 screwed to the fixed column 11.

In the structure shown in FIGS. 2 and 3, the columns 3, 11 and 12 are generally made of molybdenum material, the heater 5 is made of pyrolytic graphite or highly oriented carbon material, and the cathode tip 6 is made of rare earth boride, especially lanthanum hexaboride. Has been.

By the way, in the hot cathode holding device having such a structure, in order to obtain a stable high-intensity electron beam, the cathode chip 6, the heater 5, and the support column 3 are kept even at a high temperature of 1500 to 1600 ° C. which is the operating temperature of the cathode chip 6. Or 12 shall maintain stable electromechanical contact.

[Problems to be Solved by the Invention] The structure shown in FIG. 2 has a feature that the number of parts is small and the structure is simple, so that the cost is low and the size can be reduced.

However, in the case of this structure, the precision of the parts alone does not provide sufficient precision. Therefore, in order to assemble the cathode chip 6, the heater 5 and the column 3 with high precision, an adjustment work for bending and deforming the column 3 is performed. , The elasticity of the column 3 causes the heater 4
Is pressed to hold the cathode chip 6. In actual use, the bent portion of the column 3 is relatively hot (the operating temperature of the cathode chip 6 is a high temperature of 1500 to 1600 ° C., so the column 3
The temperature at the bending part, which is the middle part of the temperature, is around 700 ° C)
Since the residual stress due to the bending in the adjustment work is released, the pillar 3 is deformed. Therefore, during use at high temperature, the pair of left and right columns 3 are slightly deformed according to the residual stress, resulting in an imbalance in the clamping force. Move to the right or left with the passage of. As a result, the relative position between the grid electrode (not shown) arranged outside the tip of the cathode chip 6 and the cathode chip 6 changes. Further, during use under high temperature, the pair of columns 3 slightly bends in the opening direction due to the temperature difference between the inside and the outside, and the clamping force of the columns 3 decreases. As a result, the contact state between the cathode chip 6 and the heater 5 deteriorates.

As described above, when the relative position between the grid electrode and the cathode chip 6 changes, or when the contact state between the cathode chip 6 and the heater 5 deteriorates, the electron emission state from the tip of the cathode chip 6, particularly the current value and the current density. The distribution changes. Therefore, there is a problem that the current value of the finally used electron beam may temporarily leave the implementation range and become unusable.

In the structure shown in FIG. 3, since the elastic plate 13 pressed by the adjusting screw 14 is pressed against the energizing member 12, the energizing strut member 12 is used for the adjustment work.
Since there is almost no need to deform and there is little influence of residual stress, the problem of FIG. 2 is solved.

However, since this structure has a large number of partial points and a complicated structure, the cost is high. An elastic plate 13 is arranged outside the support column 3 at a constant interval, a fixed support column 11 is provided on the outer side of the elastic plate 13, and an adjusting screw is provided from the outside of the fixed support column 11.
Since 14 is screwed together, there is a problem that the size is inevitably increased.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hot cathode holding device having a column having a small number of parts, a simple structure, a low cost, and a column relatively unaffected by residual stress or thermal deformation.

[Means for Solving the Problems] The above object is to provide a hot cathode holding device in which a cathode chip is held between a pair of support columns via a pair of heaters, and a mounting portion of the support columns is provided on an upper surface of an insulating substrate. The hot cathode holding device is characterized in that the support pillar is provided so as to extend downward through the insulating substrate, and a portion near the mounting portion of the support pillar is a plastically deformable portion.

[Operation] Since the mounting portion of the pillar is provided on the upper surface of the insulating substrate and the portion near the mounting portion of the pillar is configured as the plastic deformation portion,
Adjustment work when holding the cathode chip under clamping pressure is easy, and the deformation stress associated with the deformation for that purpose is small. Further, since the plastically deformed portion of the support column is located away from the heater, the temperature rise due to heat conduction from the heater is small. For example, when the plastically deformed part is near the mounting part of the support pillar to the insulating substrate, the plastically deformed part is in a low temperature range of about 100 to 200 ° C. during use, so that residual stress is hardly released and the thermal stress does not occur. Since it is not affected, there is little deformation of the columns due to heat.

[Embodiment] An embodiment of a pillar used in the hot cathode holding device of the present invention will be described below with reference to FIG. In this embodiment, the shape of the column 3 shown in FIG. 2 is improved to the shape of the column 31 shown in FIG.
The drawbacks of the structure shown in the figure are eliminated.

The pillar 31 is provided inside the tip of the heater holding arm portion 31b, the heater holding arm portion 31b extending from the mounting portion 31a of the electrode 2 on the pillar mounting surface 2c, and the heater 5 It is the same as the support column 3 in FIG. 2 in that it is composed of a heater clamping portion 31c for clamping. The pillar 31 is entirely made of the same material,
For example, it is made of molybdenum.

In this embodiment, the mounting portion 3 separated from the heater holding portion 31c
A part of the heater holding arm portion 31b near 1a is made thin to provide a plastically deformable portion 31d. Therefore, when the hot cathode holding device is assembled using the support column 31 as shown in FIG. 2 and the cathode chip 6 is held under pressure by the heater 5, the heater holding arm portion 31b is adjusted to adjust the elastic pressure. When bending
The plastically deformable portion 31d is bent and adjusted.

Therefore, even if the heater 5 is heated to a high operating temperature (1500 to 1600 ° C.), the plastically deformed portion 31d is in a low temperature region apart from the heater 5, so that there is almost no thermal influence,
Reference numeral 31 stably maintains the electromechanical contact with the heater 5 and the cathode chip 6. Further, since it is only necessary to change the shape of the support column 31, there is almost no increase in cost as compared with that of FIG. 2 and the size is not changed. In this case, it is preferable to provide the plastically deformable portion 31d in a portion as far as possible from the heater 5, but if the position is at least ⅔ of the length of the heater holding arm portion 31b from the heater holding portion 31c side, it is practically used. No problem.

Further, in this embodiment, a slit 31e is provided between the mounting portion 31a and the heater holding arm portion 31b. As described above, when the slit 31e is provided, the length of the heater holding arm portion 31b is substantially increased, the heater holding arm portion 31b is easily bent, and the plastically deformable portion 31d is located further away from the heater holding portion 31c. It is possible to provide it in the above and is more effective.

[Effects of the Invention] As is apparent from the above description, according to the present invention, since the plastic deformation portion is provided at a position distant from the heater of the support, the number of parts is small, and when the clamping force of the cathode chip is held. Work is easy, the deformation stress associated with the deformation is small, and the thermal influence of the plastically deformed portion can be prevented with a simple structure.

[Brief description of drawings]

FIG. 1 shows an embodiment of a pillar used in the hot cathode holding device of the present invention. (A) is a front view, (b) is a side view, (c) is a bottom view, and FIG. 2 is a conventional example. Shows (a) a front view,
(B) is a side view, (c) is a plan view, and FIG. 3 is a front view showing another conventional example. 3, 31: stanchions, 31b: heater holding arm portion, 13c: heater holding portion, 31d: plastically deformed portion, 5: heater, 6: cathode chip.

Claims (2)

[Scope of utility model registration request] 1. A hot cathode holding device in which a cathode chip is sandwiched and held by a pair of supporting columns via a pair of heaters, the mounting portion of the supporting columns is provided on an upper surface of an insulating substrate, and the supporting columns pass through the insulating substrate. A hot-cathode holding device, characterized in that a portion that extends downward and is close to the mounting portion of the column is a plastically deformable portion. 2. The hot cathode holding device according to claim 1, wherein the plastically deformable portion is composed of a thin portion.