JP3264006B2 - 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 for this type of vacuum capacitor is that the loss is low.
Heat generation at the time of energization may be 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 10% IACS (International Amealed Cop).
per Standard: an intrinsic conductivity ratio with respect to international standard annealed copper), and in high frequency applications, there was a problem that the electric resistance increased during energization and the surface temperature of the vacuum capacitor rose.
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]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a vacuum pump having a bellows which keeps the inside of a vacuum container airtight following a displacement of a movable electrode and also serves as a current path to an external power supply terminal. The capacitor is characterized in that beryllium copper is used as a material of the bellows, and a copper plating process or a nickel plating process is applied to a brazing portion of the beryllium copper.

In another aspect of the present invention, in the vacuum capacitor, the entire surface of the beryllium copper is plated with a plating material having a higher conductivity than the beryllium copper, for example, a copper-based material or a silver-based material. It is characterized by the following.

In another aspect of the present invention, the above-mentioned vacuum capacitor is characterized in that the brazing portion is brazed by a brazing material of an alloy containing copper and silver.

[0012]

[Function] The frequency of the current flowing through the vacuum capacitor is several M
If on the order of H _Z, the high-frequency current is concentrated on the surface of the bellows by the skin effect, current cross-sectional area is reduced.

In the present invention, the bellows is made of beryllium copper having higher conductivity than phosphor bronze, so that a high-frequency current can easily flow. However, since beryllium copper has a strong beryllium oxide formed on its surface during brazing, a brazing material containing copper and silver is subjected to copper plating or nickel plating on the brazed portion. Can be used.

[0014] Further, by plating the entire surface of the beryllium copper with a copper-based material or a silver-based material having higher conductivity than phosphor bronze, the electrical resistance of the bellows surface is further reduced,
High-frequency current flows easily. Further, the use of the brazing material is also possible.

As a result, heat generation during energization is suppressed, and the allowable maximum current value of the vacuum capacitor increases.

[0016]

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.

(First Embodiment) In the first embodiment of the present invention,
In the vacuum capacitor having the structure shown in FIG. 1, beryllium copper (Cu-Be) is used as the material of the bellows 22.

However, when assembling a vacuum capacitor, it is necessary to braze the bellows 22 in a vacuum. In the case of beryllium copper, a strong beryllium oxide (B
eO) is formed, making brazing difficult. Therefore, copper (Cu) plating or nickel (Ni) plating is applied to the brazed portion of beryllium copper, and a brazing material containing copper and silver, for example, a Cu-Ag-Sn brazing material or Cu-Ag-In.
The use of brazing material was made possible. By using these brazing materials, brazing in a vacuum atmosphere of about 750 ° C. that does not cause deformation or the like of the bellows 22 becomes easy, and a vacuum capacitor capable of solving the conventional problems can be manufactured.

FIG. 2 is a graph showing the relationship between the current flow and the surface temperature of the vacuum capacitor according to this embodiment.
A characteristic example when beryllium copper of 2% IACS is used (beryllium copper bellows 22% IACS), and a dashed line is a characteristic example when beryllium copper having a conductivity of 48% IACS is used (beryllium copper bellows 48% IACS). Is shown. As a comparative example, phosphor bronze bellows 10% I
A characteristic example of a conventional vacuum capacitor using ACS is also indicated by a broken line. Each of these values gives a capacitance of 50
0 [pF], the use frequency 13.56 [MH _Z], applied current I (= ωCV: ω is the angular frequency, C is the capacitance, V is the applied voltage) in the example in the case of variable by an applied voltage V to is there.

Referring to FIG. 2, it can be seen that the vacuum capacitor using the beryllium copper bellows suppresses the surface temperature rise with respect to the current value more than the phosphor bronze bellows. This is because the electrical conductivity of beryllium copper is higher than that of phosphor bronze, and the current on the bellows surface easily flows. This suppresses a rise in surface temperature during energization of the vacuum capacitor, and increases the allowable maximum current value.

(Second Embodiment) In a second embodiment of the present invention,
1. A vacuum capacitor having the structure shown in FIG. 1, in which beryllium copper (Cu-Be) is used as the base of the bellows 22, and the entire surface thereof is plated with a copper-based material having higher conductivity than beryllium copper. It is. Beryllium copper having a conductivity of at least 22% IACS is used.

According to the bellows 22 made of the above material, similarly to the first embodiment, the Cu-Ag-Sn brazing material or the Cu-A
The g-In brazing material can be brazed in a vacuum atmosphere at about 750 ° C., which facilitates assembly of a vacuum capacitor.

FIG. 3 is a graph showing the relationship between the current flow and the surface temperature of the vacuum capacitor according to the second embodiment.
Copper (Cu) plating on beryllium copper of IACS (copper plated beryllium copper bellows 22% IAC
The characteristic example of S), and the dashed line indicates a characteristic example when beryllium copper of 48% IACS is subjected to copper plating (copper-plated beryllium copper bellows 48% IACS). Further, as a comparative example, an example of characteristics of a conventional vacuum capacitor using phosphor bronze bellows 10% IACS is also indicated by a broken line. These values are based on the same measurement conditions as the characteristic diagram of FIG. 2 shown in the first embodiment.

Referring to FIG. 3, the vacuum capacitor according to the second embodiment has a higher surface temperature with respect to the flowing current value than the conventional vacuum capacitor using phosphor bronze bellows and the vacuum capacitor according to the first embodiment shown in FIG. Is suppressed. This is because beryllium copper has higher conductivity than phosphor bronze, and the higher the frequency becomes, the more effective the copper plating film on the bellows surface is, and the more easily the current flows on the bellows surface. This suppresses a rise in surface temperature during energization of the vacuum capacitor, and increases the allowable maximum current value.

FIG. 3 shows an example in which beryllium copper is plated with copper (Cu). However, another copper-based material having substantially the same conductivity as copper is used as a plating material. May be. 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.

[0026]

As described above, in the vacuum capacitor of the present invention, the bellows, which keeps the inside of the vacuum vessel airtight and follows the displacement of the movable electrode and serves as a current path for the external power supply terminal, is brazed. The part is made of beryllium copper plated or nickel-plated, so that the current carrying capacity is improved compared to conventional vacuum capacitors using phosphor bronze bellows, and the heat generated during powering is suppressed. . Also, low joining in a low-temperature vacuum atmosphere becomes possible,
The assembly of the vacuum capacitor becomes easy.

In the vacuum capacitor of the present invention, since the entire surface of the beryllium copper bellows is plated with a copper-based material or a silver-based material having higher conductivity than beryllium copper, the bellows surface is formed by a skin effect. The concentrated high-frequency current flows more easily, and has the effect of further suppressing heat generation during energization.

As a result, the allowable maximum current value of the vacuum capacitor is increased, so that it is not necessary to cool the vacuum capacitor when it is housed in a circuit or a device to be used, 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 an electric current-surface temperature characteristic diagram of the vacuum capacitor according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a relation between a current flowing through a vacuum capacitor and a surface temperature according to a second embodiment of the present invention.

[Explanation of symbols]

 10: vacuum vessel 16: movable electrode 22: bellows

Continuation of the front page (56) References Hira 4-74416 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 5/14 H01G 5/01

Claims (6)

(57) [Claims] 1. A vacuum capacitor having a bellows that 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, wherein a material of the bellows is beryllium copper; A vacuum capacitor, wherein a copper plating process is applied to a brazing portion of the beryllium copper. 2. The vacuum capacitor according to claim 1, wherein nickel plating is performed instead of said copper plating. 3. The vacuum capacitor according to claim 1, wherein the entire surface of the beryllium copper is plated with a plating material having a higher conductivity than the beryllium copper. 4. The vacuum capacitor according to claim 3, wherein the plating material is a copper-based material. 5. The vacuum capacitor according to claim 3, wherein the plating material is a silver-based material. 6. The vacuum capacitor according to claim 1, wherein said brazing portion is brazed with a brazing material of an alloy containing copper and silver. .