JPH023533B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for packaging a capacitor with a round face using a plastic film having a small dielectric loss tangent as a dielectric material.

In general, capacitors using plastic film as a dielectric material are often packaged by coating with a high viscosity liquid resin in a molten state or by coating with a powdered resin. However, when these methods are applied to a round element in which the winding core hole exists as a void,
Since the voids were not sufficiently filled with resin, large pinholes were formed in the resin portion covering the surface of the winding core hole when the resin was cured, making it unsuitable as a method for packaging round elements. For this reason, a method of packaging the resin using a low-viscosity liquid resin in a molten state has been considered, but this has the drawback that the desired thickness of the packaging cannot be obtained, and is not practical. Therefore, a method of using a low-viscosity liquid resin in a molten state and coating the entire surface with powdered resin after immersing it in the liquid resin has been considered. Although it is useful in that it enables filling and prevents the occurrence of pinholes, the low viscosity liquid resin not only fills the core holes but also enters between the plastic film layers through the gaps in the metallicon. In such cases, apart from combinations in which the dielectric loss tangent of plastic film and low-viscosity liquid resin is not much different, or combinations in which the dielectric loss tangent of plastic film is larger than that of low-viscosity liquid resin, for example, polypropylene film is used as the dielectric material. In the case of combinations where the dielectric loss tangent is smaller than that of the resin, such as when using polyethylene film or polystyrene film and epoxy as a low-viscosity liquid resin, the dielectric loss tangent of the resin will have an effect as the capacitance becomes smaller. The small dielectric loss tangent characteristic of the dielectric material cannot be fully utilized, and the dielectric loss tangent of the capacitor itself is increased, resulting in a large exterior temperature rise due to heat generation during mounting.While the operating temperature range can be kept low, the capacitance decreases greatly, making the characteristics unstable. It had some drawbacks. However, such problems have been particularly pronounced in metal foil structures in which the gaps between dielectric layers are larger than in vapor-deposited structures.

The present invention has been made in view of the above points, and by performing immersion in a powder resin bath, immersion in a low viscosity liquid resin bath at room temperature, and immersion in a powder resin bath, the small dielectric loss tangent characteristic of the plastic film itself can be prevented. To provide an exterior packaging method capable of obtaining a film capacitor consisting of a round element with excellent appearance and no characteristic deterioration while ensuring an appropriate exterior thickness without pinhole defects.

The present invention will be explained below by way of an example. That is, as shown in FIG. 1, a round capacitor is formed by alternately laminating and winding a pair of polypropylene films and a pair of metal foils, forming metallicon electrodes 1 on both end faces, and connecting lead terminals 2 to the metallicon electrodes 1. After preheating the element 3 in a constant temperature bath of 90 to 110°C for about an hour, maintain the preheated state and heat it at 150°C for 30 seconds → immerse it in a powder resin tank → remove it from the powder resin tank and heat it at 150°C for 30 seconds. The process is repeated 3 to 6 times to form the first resin layer 4 on the capacitor element 3 as shown in FIG. Note that 5 is a winding core hole.
Next, the capacitor element 3 on which the first resin layer 4 has been formed is melted at room temperature, immersed in a liquid resin of 50 to 500 cps to some extent, and coated with a reduced pressure of 1/2 to 1/3 atm. The thin second resin layer 6 is formed within the winding core hole 5 and on the surface of the first resin layer 4 as shown in FIG.
℃, heating for 30 seconds → immersion in a powder resin bath → lifting from the powder resin bath and heating at 150℃ for 30 seconds for 3 to 6 steps.
This is an exterior packaging method in which the third resin layer 7 is repeatedly formed as shown in FIG.

According to the method of packaging a polypropylene film capacitor with a round element as described above, the capacitor element 4 is first coated with a powdered resin and then immersed in a low viscosity liquid resin. The resin does not enter between the polypropylene film layers through the gaps, and the small dielectric loss tangent characteristic of the polypropylene film is not lost. The entire inside of the winding core hole 6 is filled with resin, and pinholes can be eliminated. Furthermore, since the product is immersed in a powder resin bath again after being immersed in a liquid resin bath, it has the advantage of easily securing the necessary exterior thickness and exhibiting a good effect in terms of appearance.

Next, the effects of the present invention will be explained based on experimental results. In other words, it is made by combining two polypropylene films with a thickness of 6μ and a width of 20mm + one sheet of aluminum foil with a thickness of 6μ and a width of 20mm.It has a rating of 630V.DC/400V.
Thirty AC-0.01 μF round elements were prepared, 15 of them were packaged using the present invention, and the remaining 15 were packaged using the conventional method of dipping in a low viscosity liquid resin bath and dipping in a powder resin bath. Comparison of characteristics between the product of the present invention (A) obtained and the conventional product (B) obtained from the conventional example are shown in Figures 5 to 7.
Shown in the figure. In this case, both powder and liquid epoxy resins were used in the present invention and in the conventional examples, and the liquid resin had a viscosity of 350 cps at 20°C. Figure 5 shows the distribution of 10KHz-dielectric loss tangent, Figure 6 shows the temperature rise versus time when a 10KHz-100V sine wave is applied, and Figure 7 shows the constant temperature at 85℃. The figure shows the rate of change in capacitance versus time when a 10KHz-100V sine wave is applied inside the tank. From the above results, the product (A) of the present invention is superior to the conventional product (B) in all properties, demonstrating the excellent effects of the packaging method of the present invention. In the above embodiment, polypropylene film was used as the dielectric material, but the same effect can be obtained using polyethylene film, polystyrene film, or polyfluorinated ethylene film. Although the method using foil has been described as an example, it goes without saying that it can be applied to a vapor-deposited electrode structure.

As described above, according to the present invention, as a means for sheathing a round element formed by winding a plastic film with a small dielectric loss tangent, immersion in a powder resin bath, immersion in a liquid resin bath with low viscosity at room temperature, and immersion in a powder resin bath are performed. By carrying out this method, it is possible to provide a method for packaging a film capacitor which has great practical value and can provide a film capacitor with no characteristic deterioration.

[Brief explanation of drawings]

1 to 4 show the steps of a method for packaging a film capacitor according to an embodiment of the present invention. FIG. 1 is a sectional view showing a capacitor element, and FIG. 3 is a cross-sectional view showing the state in which one resin layer has been formed.
4 is a sectional view showing a state in which a second resin layer is formed on the surface of the resin layer, FIG. 4 is a sectional view showing a state in which a third resin layer is formed on the surface of the second resin layer shown in FIG. 3, and FIG. FIG. 6 is a time-temperature rise characteristic curve diagram, and FIG. 7 is a time-capacitance change rate characteristic curve diagram. 3... Capacitor element, 4... First resin layer, 5
... Winding core hole, 6 ... Second resin layer, 7 ... Third resin layer.

Claims (1)

[Claims] 1. Means for forming a first resin layer by immersing a round capacitor element wound with a plastic film having a small dielectric loss tangent in a powder resin bath; A means for forming and heating a second resin layer on the winding core hole and the surface of the first resin layer, and a means for subsequently immersing in a powder resin bath to form a third resin layer on the surface of the second resin layer. How to package a film capacitor.