JPS6018832Y2 - High voltage feedthrough capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-voltage feedthrough capacitor used as a noise filter for high-frequency, high-power devices, such as microwave ovens, magnetrons for broadcasting equipment, or X-ray tubes.

Recently, high-power electromagnetic waves in the UHF and V□ bands have come to be used not only in industrial equipment such as broadcasting equipment and medical X-ray equipment, but also in consumer equipment such as microwave ovens, and their use is increasing. As a result, prevention of noise pollution caused by electromagnetic waves leaking from these devices has become an important issue.

In order to prevent such noise pollution, various noise filters have been used in the past.

Figure 1 shows a conventional example of a high-voltage feedthrough capacitor used as a component of this type of noise filter. The electrodes 3 are fixed on the floating part 5 of the metal fitting 4 so as to be in contact with each other, and the through conductor 8 provided with the insulating tube 10 is connected to the through-hole ceramic capacitor 1 and the grounding fitting 4.
After passing through the through holes 1a and 5a provided in the floating part 5 of the through-hole ceramic capacitor 1, the electrode fitting 6 is fixed onto the electrode 2 of the through-hole ceramic capacitor 1 by means such as soldering, and the through-hole ceramic capacitor 1, The electrode fitting 6 and the penetrating portion of the through conductor 8 are covered with an insulating resin 9, and the outer periphery of the insulating resin 9 is covered with an exterior case 11.

12 is an insulating cover. The insulating resin 9 is provided to ensure insulation, moisture resistance, etc. of the through-type ceramic capacitor 1, and is formed by injecting an insulating resin such as epoxy resin into the exterior case 11.

The outer case 1 is made of synthetic resin, such as ABS, nylon, polyethylene resin, etc., which has good adhesion to the insulating resin 9, provides strong adhesion, and is flame retardant.

However, if the outer case 11 is made of a synthetic resin that exhibits adhesive properties to the insulating resin 9, the adhesive force between the outer case 11 and the insulating resin 9 will be When the insulating resin 9 hardens and shrinks, during heat cycle tests, or during heat resistance tests, residual stress generated due to differences in linear expansion coefficients of each part causes the porcelain capacitor 1 and the insulating resin to bond together. Gaps, cracks, or peeling occur at the interface of 9, and these gaps,
High electric field lines concentrate in cracks and peeled areas, which tends to cause creeping discharge damage, resulting in a lack of reliability.

In order to eliminate the above-mentioned drawbacks, there is a method in which the outer case 11 is made of a synthetic resin that is non-adhesive to epoxy resin, such as polypropylene resin, and the insulating resin 9 is cast using the outer case 11. has also been proposed.

However, polypropylene resin is flammable and too dangerous to be used as an exterior case as it is, so it must be removed after casting the insulating resin 9, resulting in poor workability, lack of mass production, and high costs. There are drawbacks.

The present invention solves the problems of the prior art described above, and is a high-voltage feed-through type with an exterior case that does not cause deterioration of temperature and voltage resistance characteristics even if it is installed as is after insulating resin is cast. The purpose is to provide capacitors.

In order to achieve the above object, the present invention is characterized in that the insulating resin surrounding the feedthrough capacitor is covered with an exterior case whose coefficient of linear expansion is smaller than that of the insulating resin.

That is, in the high voltage feedthrough capacitor as shown in FIG. 1, when the linear expansion coefficient of the insulating resin 9 is α1 and the outer case of the outer case 11 is α2, the insulating resin 9 and the insulating resin 9 are adjusted so that α1>α2. The exterior case 11 is selected.

Of course, the outer case 11 is made of a flame-retardant material.

As the insulating resin 9, flexible epoxy resins such as novolak epoxy or polyglycol type epoxy known under trade names such as Epicote and Araldite are suitable.

These epoxy resins have a linear expansion coefficient α1 of α1=9.3.
It is relatively large at approximately X10-5/°C.

Moreover, as a specific example of the exterior case 11 for this,
Synthetic resins such as polybutylene terephthalate and polyethylene terephthalate are suitable.

The linear expansion coefficient α2 of these synthetic resins is α2=2.3~
It is around 2.5 x 10-5/°C, and fully satisfies the relationship α1>α2.

As mentioned above, if the linear expansion coefficient α2 of the outer case 11 is selected to be a value smaller than the linear expansion coefficient α1 of the insulating resin 9,
When the temperature is increased in a heat cycle test or a heat resistance test, as shown enlarged in FIG. 2, the amount of expansion of the outer case 11 shown by arrows A-Q is -
Since the expansion amount of the insulating resin 9 is smaller than the expansion amount of the insulating resin 9, the expansion of the insulating resin 9 is suppressed by the outer case 11, and reactionary
A force f is applied to the interface 1b between the capacitor 1 and the ceramic capacitor 1 in the direction of increasing the adhesive force between the two.

As a result, the occurrence of gaps, cracks, peeling, etc. at the interface 1b is prevented, and the withstand voltage characteristics are significantly improved.

If the linear expansion coefficient α2 of the outer case 11 is made larger than the linear expansion coefficient α1 of the insulating resin 9, the outer case 11 will expand more than the insulating resin 9. Due to the synergistic effect of the stress that tends to cause the ceramic capacitor 1 to peel off and the stress that the exterior case 11 exerts on the insulating resin 9, the magnetic capacitor 11 and the insulating resin 9 are separated.
Gaps, cracks, or peeling occur at the interface 1b with the metal, resulting in poor withstand voltage.

FIG. 3 shows a heat cycle characteristic diagram of a high voltage feedthrough capacitor according to the present invention and a conventional high voltage feedthrough capacitor.

The straight line represents the heat cycle characteristics of the high voltage feedthrough capacitor according to the present invention, and the straight line L2 represents the heat cycle characteristics of the conventional high voltage feedthrough capacitor.

As shown by the straight line L2, the cumulative failure rate of conventional high voltage feedthrough capacitors reaches almost 100% in less than 100 cycles, but the high voltage feedthrough capacitor according to the present invention has a cumulative failure rate of almost 100% as shown by the straight line L2. ＜、With less than 100 cycles, almost no failure occurs, and the heat cycle characteristics are significantly improved.

As described above, the present invention provides that the insulating resin covering the feedthrough capacitor has a linear expansion coefficient of 11f1m
Even if the insulating resin is covered with an outer case, there will be gaps at the interface between the feedthrough capacitor and the edge resin during heat cycle tests and heat resistance tests. It is possible to provide a highly reliable high-voltage feed-through capacitor that is resistant to cracking or peeling and has excellent temperature and voltage resistance characteristics.

In addition, the outer case is made of a flame-retardant material and is left in place even after the insulating resin 9 is cast.

Therefore, it is possible to provide a high-voltage feed-through capacitor that is easy to assemble, can be mass-produced, and is inexpensive.

It goes without saying that the present invention can also be applied to other types of high voltage feedthrough capacitors, for example, double type high voltage feedthrough capacitors.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a high voltage feed-through capacitor, Figure 2 is an enlarged cross-sectional view of the main parts to explain the effects of the high voltage feed-through capacitor according to the present invention, and Figure 3 is a characteristic diagram of heat cycle. be. 1...Feedthrough capacitor, 9...Insulating resin,...Exterior case. 1

Claims (2)

[Scope of utility model registration request] (1) Insulating resin covering the feedthrough capacitor,
1. A high-voltage feed-through capacitor, characterized in that the capacitor is covered with an exterior case having a coefficient of linear expansion smaller than that of the insulating resin. (2) The high voltage feed-through capacitor according to claim 1, wherein the outer case has flame retardancy.