JP3264005B2 - Vacuum condenser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable-type vacuum capacitor used for impedance adjustment in a high-frequency power supply or a high-power oscillation circuit of a semiconductor manufacturing apparatus.

[0002]

2. Description of the Related Art FIG. 1 is a cross-sectional view of a general variable vacuum capacitor of this type. For example, a side face is formed by ceramics 12 having copper flanges 11a and 11b at both ends thereof. Are fixed conductor 13 and metal lid 14
To form a vacuum container 10 for filling a high-yield vacuum dielectric.

A plurality of substantially cylindrical electrode plates having different inner diameters are provided concentrically at regular intervals inside the fixed conductor 13 to form a fixed electrode 15.
The movable electrode 16 is formed by a plurality of cylindrical electrode plates having different inner diameters which are inserted into and removed from each electrode gap in a non-contact state. This movable electrode 16 is provided on a movable conductor 18.

The movable conductor 18 has a hollow lead 18a on the back side of the movable electrode 16, and the side surface of the hollow lead is slidably supported by a bearing 17 as shown in FIG. . An internal thread 18b is formed on the inner wall of the end of the hollow lead 18a.

Reference numeral 19 denotes a capacitance adjusting screw,
a and a male screw 19b inserted into the female screw 18b. As shown in the figure, the capacitance adjusting screw 19 is supported by a support formed at a substantially central portion of the lid 14, that is, a screw receiving portion 20 and a thrust bearing 21 for reducing rotational torque. By rotating the head 19a manually or using a motor or the like, the movable conductor 18 is rotated.
Up and down. As a result, the crossing area between the fixed electrode 15 and the movable electrode 16 changes, so that when a voltage having a different polarity is applied to both the electrodes 15, 16, the value of the capacitance generated between the electrodes is continuously changed. be able to.

Reference numeral 22 denotes a bellows made of a soft metal, one end of which is joined to the inner wall of the lid 14 and the bearing 17 so that the movable conductor 18 (movable electrode 16) can move up and down while keeping the inside of the vacuum vessel 10 airtight. And move the other end to the movable conductor 1
8. There is also a structure in which the other end is joined to the surface of the hollow lead portion 18a. Hollow lead 18a
Since the lubricating oil is insulated between the bellows 22 and the bearing 17 for guiding the bellows, the bellows 22 is configured to be energized inside the vacuum vessel 10. That is, the bellows 22 also serves as a current path between an external power supply terminal (not shown) provided on the lid 14 and the movable electrode 16.

[0007]

One of the characteristics required of a vacuum capacitor is that the loss is low and the heat generation during energization is small. In the vacuum capacitor having the above structure, the material of the bellows 22 has a great influence on the above characteristics. Conventionally, phosphor bronze is mainly used as the material of the bellows 22, but the conductivity of the phosphor bronze bellows is as follows.
10% IACS (International Amealed Copper Stan
dard: an intrinsic conductivity ratio with respect to international standard annealed copper), and there was a problem that the surface temperature of the vacuum capacitor rises during energization in high frequency applications. Therefore, the allowable maximum current value could not be increased.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a vacuum capacitor having a structure capable of increasing a high-frequency current carrying capability.

[0009]

In order to achieve the above-mentioned object, the present invention provides a phosphor bronze bellows which keeps the inside of a vacuum vessel airtight following a displacement of a movable electrode and also serves as a current path to an external power supply terminal. The phosphor bronze bellows is characterized in that a surface of the phosphor bronze bellows is plated with a plating material having a higher conductivity than phosphor bronze, for example, a copper material or a silver material.

[0010]

[Function] The frequency of the current flowing through the vacuum capacitor is several M
If on the order of H _Z, since the high-frequency current is concentrated at the extreme surface of the bellows due to the skin effect, this surface portion,
By performing plating with a plating material having a higher conductivity than phosphor bronze, electric resistance is reduced and current easily flows.
Therefore, heat generation during energization is suppressed, and the allowable maximum current value of the vacuum capacitor increases.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Since the present invention is an improvement of the conventional vacuum capacitor, the description of the same components as those shown in FIG. 1 will be omitted, and only different portions will be described.

In this embodiment, in the vacuum capacitor having the structure shown in FIG. 1, the bellows 22 is made of phosphor bronze plated by using a highly conductive plating material. Phosphor bronze is suitable for the base of the bellows 22 because it has excellent toughness, elasticity, and abrasion resistance, and also has a conductivity of about 10% IACS as described above.

FIG. 2 is a current-surface temperature characteristic diagram of a vacuum capacitor according to one embodiment of the present invention. An example of a case where copper (Cu) is used as a plating material (copper-plated phosphor bronze bellows) is shown by a solid line. I have. Further, as a comparative example, a value obtained by a conventional vacuum capacitor using a phosphor bronze bellows that is not plated is also indicated by a broken line. These values are
The capacitance is 500 [pF] and the operating frequency is 13.
This is an example in which the applied current V is 56 [MH _Z ], and the current I (= ωCV: ω is the angular frequency, C is the capacitance, and V is the applied voltage) is varied by the applied voltage V.

Referring to FIG. 2, it can be seen that a vacuum capacitor using a copper-plated phosphor bronze bellows suppresses a rise in surface temperature with respect to an energized current value more than a conventional capacitor. This is because the energizing current is concentrated on the very surface of the bellows 22 due to the skin effect, and a highly conductive plating film becomes effective. This suppresses a rise in temperature during energization, and increases the allowable maximum current value.

Although the above is an example in which copper (Cu) plating is performed, another copper-based material having substantially the same conductivity as the plating material may be used. Further, if a plating film is formed of a silver-based material such as pure silver (Ag) having higher conductivity, a bellows 22 having more excellent current-carrying ability can be obtained, which can contribute to improvement of the characteristics of the vacuum capacitor.

[0016]

As described above, according to the present invention, the surface of the phosphor bronze bellows, which keeps the inside of the vacuum chamber airtight and follows the displacement of the movable electrode and also serves as a current path to an external power supply terminal, is formed on the surface of the phosphor bronze bellows. Since the plating process is performed with a copper-based material or a silver-based material having a high rate, the current-carrying ability is improved, and there is an effect that heat generation when high-frequency current is applied is prevented. As a result, the allowable maximum current value of the vacuum capacitor is increased, and when housed in a used circuit or device, cooling of the vacuum capacitor is not required, and the reliability of the circuit and the like can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a variable vacuum capacitor to which the present invention is applied.

FIG. 2 is a diagram showing a relation between a flowing current and a surface temperature of a vacuum capacitor according to an embodiment of the present invention.

[Explanation of symbols]

 10: vacuum vessel 16: movable electrode 22: bellows

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 5/14 H01G 5/01

Claims (3)

(57) [Claims] 1. A vacuum capacitor having a phosphor bronze bellows which keeps the inside of a vacuum vessel airtight following a displacement of a movable electrode and also serves as a current path to an external power supply terminal. A vacuum capacitor characterized by being plated with a plating material having a higher conductivity than that of a vacuum capacitor. 2. The vacuum capacitor according to claim 1, wherein the plating material is a copper-based material. 3. The vacuum capacitor according to claim 1, wherein the plating material is a silver-based material.