JPS6130413B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a film capacitor, and its purpose is to use the same resin for impregnating the inside of a film capacitor element and for the exterior for protecting the element from the external environment. It is an object of the present invention to provide an economical method for manufacturing a film capacitor that saves steps and materials by making the resin layer on the element surface thicker than other parts.

So-called film capacitors, which use plastic film as a dielectric, are electronic components that are used in extremely large quantities for electronic devices. Among these, the most common method of manufacturing a resin-clad capacitor is as follows.

In other words, a low-viscosity thermosetting resin such as an epoxy resin is used for the flat pressed element, and if necessary, it is placed under reduced pressure (e.g.
Impregnated at a pressure of 0.1 atmosphere or less) and heated to harden. Then, it is dipped in a highly viscous and highly thixotropic resin, for example, an epoxy resin, and then heated to harden the curable epoxy resin or epoxy resin. A large amount of thermal energy is required to cure the deposited impregnation and sheath resin. In addition, in the case of mass production of capacitors, large-sized heating devices were required for impregnation and packaging.

Attempts have been made to use a single resin for both impregnation and packaging in order to avoid the trouble of having to use separate resins for the two steps of impregnation and packaging, as described above, but these methods are still effective. The reason why this method has not been used is as follows.

The impregnation process is performed to fix the inside of the element by infiltrating the resin into the element and hardening it, and to increase the external strength of the element in the later packaging process and at the same time to improve the airtightness of the element. Therefore, the resin used for impregnation must have low viscosity and good permeability. However, if only the impregnation process is used, the amount of resin adhered to the element surface is small, especially the end face where the multilayer formed by winding the film and electrode foil is exposed.
It is not possible to electrically and mechanically protect the device from the external environment. On the other hand, when the exterior is applied directly without going through the impregnation process, there are a lot of voids inside the element, so when heating to harden the exterior resin,
A large number of bubbles are generated on the exterior surface, and the inside of the device is not isolated from the outside world, so that the purpose of the exterior is not achieved.

The film capacitor manufacturing method of the present invention solves these problems of the prior art and provides an economical manufacturing method.

The gist of the present invention is as described in the claims, but further explanation is as follows. A flattened film capacitor element is impregnated with a resin that has both ultraviolet curing properties and thermosetting properties, and ultraviolet rays are irradiated onto the element surface except for at least one of the end faces of the element having multiple wound layers, and the ultraviolet irradiated surface is Cure the resin until it is dry to the touch.
Since the impregnated resin has ultraviolet curing properties, only the resin on the surface irradiated with ultraviolet rays is cured, but the resin on at least one of the end faces of the element that was not irradiated with ultraviolet rays and the resin inside the element remain uncured. The element is then heated and pressurized to harden the uncured resin. At this time, as the element is pressurized, excess of the impregnated resin is pushed out toward the end face that was not irradiated with ultraviolet rays and hardened. Therefore, the resin layer on that surface is formed thicker than on other parts. That is, when it is desired to form a thicker protective outer resin layer on the end face of the element than on other parts, this purpose is achieved by excluding ultraviolet irradiation.

Next, embodiments of the method of the present invention will be described with reference to the drawings. That is, FIG. 1 is a front view (a) and a plan view (b) of a film capacitor element before impregnation, in which the wound element is substantially flattened. In the figure, 1 is a capacitor element, and 2 is a lead wire. In the method of the present invention, the capacitor element described above is impregnated with a resin having both ultraviolet curability and thermosetting properties. The impregnation method involves dipping the element 1 in the above-mentioned liquid resin, and if this is done under reduced pressure, the resin will more effectively penetrate into the element. FIG. 2 is a front view (a) and a plan view (b) of an element impregnated with the above resin. In the figure, the thickness of the resin 3 adhered is shown enlarged for easy viewing. The element shown in Fig. 2 is irradiated with ultraviolet rays except for one or both end faces of the element having the multilayered windings (i.e., the surface from which the lead wire 2 is led out and the bottom surface on the opposite side). Allow the resin on the UV irradiated surface to harden to the extent that it is dry to the touch. In this example, a case was shown in which both end faces of the element were not irradiated with ultraviolet rays. Even if the resin on the surface irradiated with ultraviolet rays is cured, the resin inside the element and the resin attached to the end face of the element that is not irradiated with ultraviolet rays remain uncured. Then, in the method of the present invention,
The above element is heated and pressurized to complete the exterior. The molding method may be by molding using a metal mold or the like, or by pressurizing with a press machine equipped with a hot plate. By heating and pressurizing, uncured excess resin inside the element is pushed out and transferred to the element end face, and the resin layer on the element end face becomes thicker than the resin layer on other parts. . FIG. 3 shows the element after this sheathing, in which a is a front view and b is a plan view. The thickness of the resin layer at the end face d ₁ and d ₂ in the figure
is shown to be thicker than the resin thickness d in other parts. It is well known that moisture, which is a major factor in deteriorating the characteristics of film capacitors, enters into the device mainly from the end faces, and the method of the present invention can thicken the outer resin layer on the end faces. is particularly effective as a moisture proofing measure for capacitors. Note that FIGS. 4 and 5 show an example in which only one of the end faces is excluded and the resin layer is thickened on that face during ultraviolet irradiation. That is, Fig. 4 shows the capacitor when the resin layer _d3 on the end face on the lead wire side is made thicker, and Fig. 5 shows the capacitor when the resin layer _d4 on the end face on the opposite side to the lead wire side is made thicker. Front view, b is a plan view. In any case of the elements shown in FIGS. 3 to 5, the inside of the element is fixed by hardening of the impregnated resin.

Next, the effects of the method of the present invention will be described. As described above, since impregnation and packaging are performed with one type of resin, materials and man-hours are saved, and management of resin materials is simplified. Generally, resins with high viscosity and high thixotropy tend to have a short pot life, but not using such resins is a great advantage. Furthermore, the equipment for curing the thermosetting resin can be smaller than in the case of conventional packaging methods, and the consumption of thermal energy is also greatly reduced. Further, by thickening the resin layer at the end face portion of the element which is susceptible to external environmental conditions such as humidity, the effect of protecting the capacitor can be increased. Taken together, it is clear that the method of manufacturing a film capacitor according to the present invention is far more economical than conventional methods.

[Brief explanation of the drawing]

1 to 5 are drawings showing embodiments of the present invention, in which a in FIG. 1 is a front view of a capacitor element before impregnation, b is a plan view thereof, and a in FIG. 2 is an element impregnated with resin. 3, a is a front view of the capacitor after packaging, b is a top view, a is a front view of the capacitor after packaging, and b is a top view of the capacitor after packaging. In Fig. 5, a is a front view of the capacitor after packaging, and b is a plan view. In these figures, 1...capacitor element, 2...lead wire, 3...
... Resin, d, d ₁ , d ₂ , d ₃ , d ₄ ... Indicates the thickness of the resin layer.

Claims (1)

[Claims] 1 A nearly flat film capacitor element is impregnated with a resin that has both ultraviolet curability and thermosetting properties,
irradiating the element surface with ultraviolet rays except for at least one end face of the element having the wound multilayer, and curing the resin on the ultraviolet irradiated surface to the extent that it is dry to the touch;
A method for manufacturing a film capacitor, which comprises: then molding the element by heating and pressurizing it, and making the resin layer on the end face of the element, which is not irradiated with ultraviolet rays, thicker than other parts.