JPH04332111A - Lamination-type film capacitor and its manufacture - Google Patents

Abstract

PURPOSE:To enable a creeping discharge to be restricted by forming a film with at least an organic material as one constituent element on a cutting surface by cutting. CONSTITUTION:Approximately 500 band-shaped metallized films where a metal thin film 2 is formed by depositing aluminum are laminated on a polyester film 1. An external electrode is formed on its both end faces. A capacitor base material 4 which is obtained by it is fixed to a fixing stand 5 by an adhesive tape and is cut by a rotary whetstone blade 7 while spraying pure water, thus obtaining a lamination-type film capacitor. When a cooling agent, a rotary blade, and other cutting conditions are set properly, a dielectric film 1 and a protection film are moved due to cutting and a film 3 consisting of an organic material is formed on the cutting surface, thus preventing a creeping discharge from occurring.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer film capacitor having conditions effective for improving dielectric strength and moisture resistance, and a method for manufacturing the same.

0002

2. Description of the Related Art In recent years, as electronic devices and the like have become more densely packaged, electronic components used therein have been required to be made into chips and have higher reliability. Film capacitors are also being made into chips. In order to make film capacitors into chips, miniaturization and increased capacitance have been achieved by using a laminated type in which dielectric thin films are laminated.

A conventional multilayer film capacitor will be explained below. A laminated film capacitor is made by cutting a capacitor base material into which external electrodes are attached to both end surfaces of a plurality of laminated metallized films. The cut surface of the multilayer film capacitor made in this way has a structure in which the edge of the thin metal layer on the metallized film is broken when the element is cut, and the edge of the thin metal layer is inside the cut surface. ing. This structure is shown in FIG. In the figure, 1 is a plastic film, 2 is a thin metal layer formed on the surface of the film 1, and L is the width of the thin metal layer 2 extending beyond the edge of the film 1. By adopting such a structure, the creepage distance between the edges of the thin metal layer is increased, and the electrical dielectric strength of the cut surface is maintained.

0004

However, even with the structure as described above, the electrical dielectric strength of the cut surface is actually smaller than that of the opposing electrode portion, and creeping discharge is likely to occur at the cut surface. Therefore, the rated voltage of a multilayer film capacitor is controlled by the electrical dielectric strength of the cut surface. In addition, conventional laminated film capacitors have a problem of reduced moisture resistance due to gaps between metallized film layers near the cut surface.

The present invention is intended to solve these problems, and aims to improve the electrical dielectric strength and moisture resistance of a cut surface of a multilayer film capacitor.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the multilayer film capacitor of the present invention has a film having at least an organic material as one component formed on the cut surface by cutting.

[0007]

[Function] In the multilayer film capacitor having the above structure, a film having at least an organic material as one component is formed on the cut surface by cutting to cover the cut surface, thereby suppressing creeping discharge. Furthermore, since the gaps between the metallized film layers on the cut surface are covered with a film containing at least an organic material as one component, the intrusion of moisture and the like is suppressed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a multilayer film capacitor according to an embodiment of the present invention. In FIG. 1, numerals 1 and 2 are the same plastic film and thin metal layer as in the conventional example shown in FIG. 3 is a film made of an organic material formed on the cut surface, which is a feature of the present invention. The film 3 made of this organic material is formed to cover the cut surface and is integrated with the edge of the film 1.

FIG. 2 is a perspective view of the cutting step in an embodiment of the method for manufacturing a multilayer film capacitor according to the present invention. In FIG. 2, after a capacitor base material 4 is fixed on a fixing table 5, it is cut by a rotary grindstone blade 7 while spraying a coolant 6 to obtain a capacitor element 8.

A specific example of the multilayer film capacitor constructed as above and its manufacturing method will be described. Approximately 500 belt-shaped metallized films were laminated on polyester film 1 by vacuum deposition to form metal thin layers 2, and external electrodes were formed on both end faces by metal spraying. The capacitor base material 4 thus obtained was fixed to a fixing table 5 with adhesive tape, and while spraying pure water as a coolant 6, a rotary grinding wheel blade 7 (blade diameter 75 mm,
A multilayer film capacitor with a capacitance of 100 nF was obtained by cutting with a blade thickness of 0.5 mm and an average abrasive grain diameter of 0.2 mm. The purpose of spraying pure water as the coolant 6 is to prevent the grindstone from becoming easily clogged with excessive molten film if the temperature of the cut section becomes too high, and to form an appropriate insulating film 3 on the cut surface. It's for a reason. At this time, the film 3 formed on the cut surface and made of an organic material, that is, the film mainly composed of polyester, had a thickness of about 0.003 mm.

As a comparative example, the capacitor base material was coated with oil (
A rotary saw blade (blade diameter 75 mm) is used as a coolant (mineral oil for transformers) as a coolant.
mm, blade thickness 0.5 mm, number of blades 72, carbide blade) is 10
A 0 nF multilayer film capacitor was obtained. When the cut surface at this time was observed, no film was formed as in this example, and the edge of the thin metal layer penetrated into the interior from the cut surface, as shown in FIG.

Comparing the average breakdown voltages of the laminated film capacitors obtained in this example and comparative example, the average breakdown voltage of the laminated film capacitors of this example was 300V, and that of the comparative example was 230V.

[0014] Furthermore, as a result of conducting a humidity resistance test in an atmosphere of 60°C and 90% RH, it was found that the time required for the capacitance to reach 75% of the initial value was 4500 hours for the comparative example multilayer film capacitor. On the other hand, the laminated film capacitor of this example lasted for more than 7,000 hours.

As described above, in the multilayer film capacitor of the present invention, when the cutting conditions such as the coolant and the rotary blade are appropriately set, the dielectric film 1 and the protective film are moved by cutting, and the cut surface is made of an organic material. Since the film 3 is formed, creeping discharge does not occur. Therefore, it is possible to obtain higher electrical dielectric strength than the conventional one. Furthermore, since the gaps between the metallized film layers at the cut surface are covered with this film, it is possible to prevent the intrusion of moisture and flux during board mounting, thereby improving reliability.

Although the thickness of the film formed in this example was approximately 0.003 mm, the present invention is not limited to this thickness. Furthermore, although a rotary abrasive blade was used in the cutting process of this example, the present invention is not limited to this, and the purpose of the present invention can be achieved by selecting the method, conditions, etc. so as to form a film made of an organic material. It is something. Moreover, a coolant other than water may be used.

[0017]

Effects of the Invention As described above, since the multilayer film capacitor of the present invention has a film made of an organic material on the cut surface, creeping discharge does not occur on the cut surface, there is no intrusion of moisture, etc., and the electrical dielectric strength is improved. and improved moisture resistance. Furthermore, the reliability of the multilayer film capacitor can be improved, and since the dielectric material can be made thinner, the capacitor can be made smaller and have a larger capacity.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a cut surface of a multilayer film capacitor according to an embodiment of the present invention.

FIG. 2 is a perspective view of the cutting process of a multilayer film capacitor according to an embodiment of the present invention.

[Figure 3] Cross-sectional view of a conventional multilayer film capacitor

[Explanation of symbols]

1 Film 2 Metal thin layer 3 Film made of organic material 4 Capacitor base material 6 Coolant 7 Rotary whetstone blade (grindstone blade)

Claims (4)

[Claims] Claim 1: A multilayer film capacitor in which a plurality of metallized films are laminated and separated into individual capacitors by cutting, wherein a film having at least an organic material as one component is formed on the cut surface by cutting. multilayer film capacitor. 2. A step of laminating a plurality of metallized films, a step of attaching external electrodes to both end surfaces of the metallized film to form a capacitor base material, a step of cutting the capacitor base material, and a step of cutting the capacitor base material. A method for manufacturing a multilayer film capacitor, comprising the step of forming a film containing at least an organic material as one component on a cut surface when cutting a base material. 3. The method for manufacturing a multilayer film capacitor according to claim 2, wherein in the cutting step, cutting is performed using a grindstone blade. 4. The method for manufacturing a multilayer film capacitor according to claim 3, wherein in the cutting step, cutting is performed while spraying a coolant onto the cut surface.