JPH0231849B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves inserting a strip of plastic film between electrode plates provided with external terminals, wrapping the same plastic film around the outer periphery of the electrode plate, and then heat-treating the element while pressurizing it. The present invention relates to a method for manufacturing a small and small capacity plastic film capacitor, which is characterized by obtaining particularly high capacitance accuracy by fusing plastic films together.

Film capacitors have been used as small-capacity capacitors used in consumer equipment such as televisions and radios because ceramic capacitors have problems in electrical characteristics and miniaturization. BACKGROUND ART Conventionally, methods for manufacturing small-capacity capacitors using plastic film as a dielectric material have been proposed, which are easy to manufacture and have good electrical characteristics. Examples of this include inventions and devices such as (a) Utility Model Publication No. 38-9061, (b) Japanese Patent Publication No. 38-21428, and (c) Japanese Patent Publication No. 20667-1974.

In the idea (a), the exterior mold of the capacitor is sealed with polyethylene, which has a lower melting point than the high melting point polyethylene dielectric plate between the capacitor electrodes, and the exterior molding process is relatively easy, but overall The heat resistance of the capacitor decreases, and the exterior mold easily deforms when used at high temperatures or when soldered, causing problems such as failure of the capacitor terminals and changes in capacitance.

In addition, in the invention (b), a pair of electrodes with lead wires connected is held in a mold, and a synthetic resin such as polyethylene is injection molded, so that the dielectric layer and the capacitor jacket are integrally made of the same material. This is an injection molding method. Here, if the dielectric layer between the electrodes is thin, there is a problem that the dielectric plastic flows poorly and becomes non-uniform, making it difficult to ensure reliability and uniformity.

In addition, in the invention (c), a plastic film is inserted between electrodes having lead wires, and this is sandwiched between a pair of plastic sheets made of the same material as the plastic film on the outside of the electrodes, and bonded and bonded using an ultrasonic welder. This is a capacitor manufacturing method that seals and cuts at the same time. Although this method is relatively simple as a manufacturing method, requires short working time, and has high productivity, it is very difficult to achieve uniform adhesion and sealing in the sense of close contact using ultrasonic waves. Also, since there is a step between the metal plate electrode part and the outer peripheral part,
The shape and pressure will be non-uniform, making uniform adhesion difficult. For this reason, when used at high temperatures or soldered, the outer casing may peel off or deform, and the capacitance may change.

Next, as an improvement to the invention method described in (c) above, there is a conventional manufacturing method in which the adhesive sealing process using an ultrasonic welder is replaced with heating and pressurizing in a furnace, which requires a much longer processing time. It's been coming.
This method is called (d). However, even in this case, adhesion and sealing were still insufficient, and adhesive parts of the plastics peeled off at high temperatures. As a countermeasure to this problem, by coating the film capacitor with a thermosetting epoxy range with excellent heat resistance, performance and reliability can be improved, including reinforcing the terminal part against short-term high-temperature loads such as soldering. was realized, but the cost was high, and the performance improvement as a capacitor was still insufficient, and the high frequency electrical characteristics of the exterior epoxy resin were not good, resulting in some deterioration of the capacitor performance.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a method for manufacturing a small capacity plastic capacitor that improves reliability and performance and reduces manufacturing costs. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below with reference to embodiments. 1 to 5 show embodiments of the present invention, FIG. 1 is a perspective view of upper and lower electrode plates superimposed on both sides of a plastic film strip, and FIG. 2 is a perspective view of the plastic film strip in the state shown in FIG. 1. A perspective view of the remaining portion wound around the upper and lower electrode plates, Figure 3 A and B are A-A and B-B in Figure 2.
4 is a perspective view of the completed product, FIG. 5 is an explanatory diagram of pressurization and heat treatment of a capacitor element, and FIG. 6 is an explanatory diagram showing a conventional manufacturing process of a capacitor element.

First, as shown in FIG. 1, flag-shaped upper and lower electrode plates 1,
1' are aligned and overlapped with each other. The upper and lower electrode plates 1, 1' are made of copper plates with a thickness of about 0.3 mm by press working or the like into a predetermined shape, and the surfaces are plated with silver for soldering or the like. Upper electrode plate 1
A relatively narrow terminal 2 is suspended below the left edge of the rectangular electrode portion 1A, and the terminal 2 is provided with a shoulder portion 2A for convenient attachment to a printed circuit board or the like. Further, the lower electrode plate 1' is rotationally symmetrical with the upper electrode plate 1, and like the upper electrode plate 1, the electrode part 1'
A, a terminal 2', and a shoulder 2'A are provided. The strip-shaped plastic film 3 has electrode portions 1A and 1'A in width.
Use a wider heat shrinkable thermoplastic range. As an example, a thickness of about 5 to 200μ manufactured by Mitsubishi Plastics Co., Ltd.
Styrofoam film (trade name Styrex) was used. This strip-shaped plastic film 3 is inserted between the electrode portions 1A and 1'A of the upper and lower electrode plates 1 and 1' facing each other over a predetermined area as shown in FIG. 1 so that the terminals 2 and 2' are exposed to the outside. Next, the extended portion of this strip-shaped plastic film 3 is wound around the outer periphery of the electrode portions 1A, 1'A of the electrode plates 1, 1', and a high-temperature tool such as a soldering iron is pressed at the end to heat-seal the ends. By fixing them together, a semi-finished capacitor element 4' as shown in FIG. 2 is obtained.

Next, as shown in FIG. 5, the capacitor element 4' as a semi-finished product made in this way is made of a material with good thermal conductivity such as aluminum with a heat-resistant elastic material 5 such as a silicone rubber sheet pasted on the inside. It is sandwiched between a pair of metal plates 6, 6, and is further pressurized by a tightening device 8 via reinforcing plates 7, 7 made of rigid metal arranged on the upper and lower outer sides thereof. Here, a spacer 9 is inserted between the plurality of capacitor elements 4' sandwiched between the metal plates 6, 6, but the spacer 9 may be used to set the thickness of the capacitor. Next, heat treatment is performed in a furnace, and in the case of the styrene film, pressure and heat treatment similar to the above are simultaneously performed using a press mold or the like for about 110° for 1 hour. As a result, the wound laminated plastic film 3 shrinks and fuses together to become an integral body, and is also adhered to and hermetically sealed with the electrode plates 1 and 1', resulting in a rectangular box-shaped finished product as shown in FIG. Capacitor 4 is obtained.

In the capacitor 4 obtained by the above-described manufacturing method, a seamless and uniform range layer is formed around the terminal in the film covering part of the outer periphery, and the film covering part of the outer periphery does not peel off. There is no When heat treated at 100° for 5 minutes, the multilayer capacitor obtained by the conventional manufacturing method including (d) above was deformed or peeled off in a considerable number of cases, but the capacitor according to the present invention There were no such failures at all.

Here, the conventional manufacturing methods (c) and (d) above will be briefly explained with reference to FIG. In the figure, Figures 1 to 3 are
Upper and lower electrode plates 1, 1', terminals 2, 2', etc., which are substantially the same as those of the present invention explained in the figures, are designated by the same reference numerals. In the manufacturing methods (c) and (d) above, the plastic film 13 is not in the form of a strip, and therefore the extended portion of the plastic film 3 is not wound around the outer periphery of the electrode plates 1, 1' as in the present invention. Instead, a plastic film 13 wider than the electrode portions is placed between the electrode portions 1A and 1′A of the upper and lower electrode plates 1 and 1′.
Next, a plastic film 13 that is wider than the electrode parts and plastic plates 13' and 13'' of the same quality are stacked on the outside of the electrode parts 1A and 1'A, heated and crimped to produce a capacitor. Board 1
A, plastic film 13 around 1'A,
Non-uniform defects remain in the bonded portions of the plastic films 13', 13'', and the plastic films 13, 13',
13'' tends to shrink along the layer surface at high temperatures, resulting in shape deformation and mutual peeling due to internal stress.

As described above, the present invention involves winding a thermoplastic film having self-adhesive properties between and around two electrode plates, heating the film while pressurizing it, and thereby forming a film between the wound plastic films. Since the capacitor was manufactured by heat-sealing and sealing the inside, it has the following excellent effects.

Since the wound plastic films are heat-sealed and adhered to each other, the inside can be reliably sealed. Moreover, since the terminal is formed integrally with the electrode plate, the periphery of the terminal also comes into close contact with the fused plastic film, and this area can also be easily sealed. Therefore, there is no need to put an exterior on it,
Therefore, highly reliable capacitors can be manufactured at low cost. Also, there is no peeling of the films of the manufactured capacitors.

In addition, thermal deformation of the capacitor is small, and the facing area between the electrode plates and the thickness of the interposed film are maintained accurately, resulting in high capacitance accuracy and little capacitance change.

[Brief explanation of drawings]

1 to 5 show embodiments of the present invention.
The figure is a perspective view of upper and lower electrode plates superimposed on both sides of a plastic film strip, Figure 2 is a perspective view of the remaining portion of the plastic film strip wrapped around the upper and lower electrode plates in the state shown in Figure 1, and Figures 3A and B. are sectional views taken along A-A and B-B in Fig. 2, Fig. 4 is a perspective view of the finished product, Fig. 5 is an explanatory diagram of pressurization and heat treatment of a capacitor element, and Fig. 6 is a conventional manufacturing of a capacitor element. It is an explanatory diagram showing a process. 1: upper electrode plate, 1': lower electrode plate, 2: upper electrode plate terminal, 2': lower electrode plate terminal, 3: strip-shaped plastic film, 4': capacitor element before heat treatment, 4: capacitor element, 5: Heat-resistant elastic body, 6: Metal plate, 7: Reinforcement plate, 8: Tightening device,
9: Spacer.

Claims (1)

[Claims] 1. A process of press-working a metal plate to produce two electrode plates integrally equipped with terminals, and a process of forming a belt-shaped self-bonding thermoplastic plastic film between the two electrode plates. A step of sandwiching a part of the plastic film, winding the remaining part around the outer periphery of two electrode plates, and heating the end of the plastic film to seal it on the plastic film. A method for manufacturing a small-capacity plastic film capacitor, which comprises the steps of heat-treating laminated plastic films while applying pressure from above and below, and heat-sealing and forming the plastic films. 2. The method for manufacturing a small-capacity plastic film capacitor according to claim 1, characterized in that a heat-shrinkable styrene film is used as the thermoplastic film with self-bonding properties.