JP2739822B2 - Feed-through capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedthrough capacitor and, more particularly, to a composite feedthrough type condenser having two dielectrics and having a large capacity.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing an example of a conventional feedthrough capacitor, and FIG. 4 is an exploded perspective view. A cylindrical dielectric (for example, porcelain ceramic or the like) 2 having an outer surface and electrodes 3 and 4 on the inner surface is inserted into a metal case 1 having a threaded portion for housing insertion and fixing. The inner wall above the threaded portion and the outer electrode 3 of a cylindrical dielectric are connected by soldering. Further, the through terminal 5 is inserted into the through hole of the cylindrical dielectric 2, and the through terminal 5 and the dielectric 2 are inserted.
Are connected by soldering. Further, the space inside the other metal case 1 is filled with an insulating resin 6.

[0003]

In a conventional feedthrough capacitor, one cylindrical dielectric inside a metal case forms the capacitor.

Therefore, when forming a feedthrough capacitor having excellent temperature characteristics (for example, CH: 0 ± 60 ppm / ° C.), it is necessary to use a dielectric having the same temperature characteristics of CH as the cylindrical dielectric. However, in general, a dielectric having a good temperature characteristic has a low dielectric constant and has a dimensional restriction that the dielectric must be accommodated in a metal case, so that C = ε (s / d) (C: capacitance, ε: dielectric , S: dielectric surface area, d: dielectric thickness), it is impossible to realize a capacitor having a capacitance larger than that represented by the following formula:

For example, if the outside diameter of the cylindrical dielectric of the conventional feedthrough capacitor is φ3 and the length is 3 mm, the capacitance is about 30 pF even when the above ceramic material is used. The temperature characteristic of the capacitance at this time is 10 to 20 pF.
It is. This kind of feedthrough capacitor has a limit of about 40 pF due to the above-mentioned restrictions.

SUMMARY OF THE INVENTION In view of the above drawbacks, an object of the present invention is to provide a feedthrough capacitor having excellent temperature characteristics, satisfying dimensional restrictions, and having a large capacitance value.

[0007]

In order to solve the above-mentioned problems, a feed-through capacitor according to the present invention is provided with an internal and external capacitor instead of an insulating resin filled inside a housing insertion portion of a conventional feed-through capacitor. A second cylindrical dielectric having an electrode on the side surface of the second dielectric.

[0008]

The conventional first cylindrical dielectric and the second cylindrical dielectric located above the housing insertion part have opposite positive and negative temperature coefficients, respectively, and have a dielectric constant larger than that of the zero temperature coefficient. Is used, a large-capacity feed-through capacitor with good temperature characteristics can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing one embodiment of the present invention,
FIG. 2 is an exploded perspective view. Inside a metal case 1 having a threaded portion for housing insertion and fixing, a first cylindrical dielectric 2 having electrodes 3 and 4 on the outer and inner surfaces and a first and second electrode 9 and 10 like the first. The two cylindrical dielectrics 8 and the first and second dielectrics are inserted with bead-shaped spacers 7 made of an insulating resin interposed therebetween so as to be insulated and separated from each other so as not to apply stress. The through terminals 5 are inserted into the through holes of the first and second cylindrical dielectrics 2 and 8 and the spacer 7, and the electrodes 3 of the first cylindrical dielectric 2 and the electrodes 9 of the second cylindrical dielectric 8 are inserted. Are connected to the inner wall of the metal case 1 and the electrodes 4 and 10 are connected to the through terminals 5 by soldering. Further, an insulating resin 6 is filled in a space in the case above the threaded portion of the metal case 1.

As the first cylindrical dielectric 2, a dielectric having a temperature coefficient of zero is used, and as the second cylindrical dielectric 8,
A dielectric having a temperature coefficient opposite to that of the first cylindrical dielectric 2 is used. In this embodiment, the first cylindrical dielectric has a dielectric constant greater than CH (0 ± 60 ppm / ° C.) and a ceramic LH (−80 ± 80) having a negative (or positive) temperature coefficient. 60 ppm / ° C.), but the ceramic AH (+ 100 ± 60p) is provided in the second cylindrical dielectric.
pm / ° C).

Here, the inner diameter of the first cylindrical dielectric 2 is a
1 [m], the outer diameter is b1 [m], the length is 11 [m], the relative dielectric constant is εS1, and the inner diameter of the second cylindrical derivative 8 is a2.
[M], the outer diameter is b2 [m], the length is l2 [m], the specific permittivity is εS2, the vacuum permittivity is ε0, and the relative permittivity of a dielectric material having a zero temperature coefficient is εS0. 1 cylindrical dielectric 2
Is expressed as follows: C1 = 2πεS1 · ε0 · l1 / {2.3 × log10 (b1 / a1)} (1) Similarly, the capacitance C2 obtained from the second cylindrical dielectric 8 is expressed as follows: C2 = 2πεS2 · ε0 · l2 / {2.3 × log10 (b2 / a2)} (2) Therefore, the amount of change due to each temperature is: dc1 / dT = 2πε0 · l1 / {2.3 × log10 (b1 / a1)} · dεS1 / dT dc2 / dT = 2πε0 · l2 / ｛2.3 × log10 (b2 / A2)｝ · dεS2 / dT In the above equation, a1, b1, l1, dε1 / dT, a2, b such that dC1 / dT = −dC2 / dT.
By selecting 2, l2 and dε2 / dT, the mutual temperature characteristics are canceled out, and a feedthrough capacitor having a temperature characteristic close to zero can be obtained.

The capacitance C of the entire feedthrough capacitor is:
Since it is given by C = C1 + C2, it is given by the following equation.

C = C1 + C2 = 2π · ε0 / 2.3 × {εS1 · 11 / log10 (b1 / a1) + εS2 · 12 / log10 (b2 / a2)} (5) Next, the first and second cylinders When dielectrics having the same zero temperature coefficient (0 ppm / ° C.) are used for the type dielectrics 2 and 8, the capacitance C0 of the entire feedthrough capacitor is C0 = 2π · ε0 / 2.3 · εS0 × ｛b1 / log10 (b1 / a1) + b2 / log10 (b2 / a2)｝ (6) In the equations (5) and (6), εS1> εS0, εS2>
From εS0, C> C0 As described above, in addition to the first cylindrical dielectric, a second cylindrical dielectric having a dielectric constant opposite to that of the first cylindrical dielectric is provided in the metal case, so that a larger capacitance can be obtained. become. Except for having the second cylindrical dielectric, the dimensions and the shape are the same as the conventional one, and when a second cylindrical dielectric having a diameter of 2.2 and a length of 4.5 mm is provided, the total capacitance of the capacitor is reduced to about 100 pF. Become. Further, the temperature characteristics are maintained at the same level as the conventional one.

As described above, according to the feedthrough capacitor of the present invention, the temperature characteristic is maintained at the same level as that of the related art, and the capacitance of about 100 pF, which is twice or more than that of the related art, can be realized.

[0016]

As described above, the feedthrough capacitor according to the present invention has a structure in which the second dielectric is also provided inside the housing insertion portion of the metal case.
It is possible to select and use a material having a positive / negative temperature coefficient having a larger dielectric constant than the dielectric material having a zero temperature coefficient. This makes it possible to realize a feedthrough capacitor having excellent temperature characteristics and having a large capacitance value.

[Brief description of the drawings]

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

FIG. 2 is an exploded perspective view showing an embodiment of a feedthrough capacitor according to the present invention.

FIG. 3 is a sectional view showing an embodiment of a conventional feedthrough capacitor.

FIG. 4 is an exploded perspective view showing an embodiment of a conventional feedthrough capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Metal case 2 ... 1st cylindrical dielectric 3 ... Electrode 4 ... Electrode 5 ... Through terminal 6 ... Insulating resin 7 ... Spacer 8 ... 2nd Cylindrical dielectric of 9 ・ ・ ・ Electrode 10 ・ ・ ・ Electrode

Claims (5)

(57) [Claims] A metal case having a threaded portion; a through terminal connected to the outside; a first electrode on an outer surface electrically connected to the metal case; A first dielectric having a second electrode electrically connected to the through terminal; a third electrode on an outer surface electrically connected to the metal case; A second dielectric, which has a fourth electrode electrically connected to the through terminal, and is arranged so as not to contact the first dielectric; and a space inside the metal case is filled. comprises a first insulator which is, wherein the second dielectric and said first dielectric positive and negative to each other
A feed- through capacitor, which is a dielectric having an inverse temperature coefficient . 2. The feedthrough capacitor according to claim 1, wherein both the first dielectric and the second dielectric are cylindrical. 3. The semiconductor device according to claim 2, further comprising a second insulator between said first dielectric and said second dielectric.
The feedthrough capacitor as described. 4. The feedthrough capacitor according to claim 4, wherein the temperature coefficient of the capacity of the feedthrough capacitor is substantially zero. 5. The feedthrough capacitor according to claim 5, wherein the first dielectric and the second dielectric are made of ceramic.