JPS59215714A - Method of producing film capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention The present invention provides a film capacitor in which polyethylene terephthalate films as a dielectric material and metal electrodes such as aluminum foil are wound or laminated alternately, or single-sided metallized polyethylene terephthalate films are stacked on top of each other. It relates to improvement of heat resistance, especially heat resistance during soldering and dipping.

In recent years, there has been an increasing demand for smaller and thinner electronic components in order to increase the density of mounting them on mounting boards, and one trend is the rise and use of chip-type components.

Ceramic capacitors and tantalum solid capacitors have been made into chips from an early stage. The electrode terminal portions of these chip-type components are placed directly on the conductor land portions of the mounting board. Therefore, whether soldering is done using the immersion method or a complete reflow soldering process, the temperature for chip-type parts is 250-270°C.
Since it will be exposed to nearby high temperatures, it is required to have excellent heat resistance. In this respect, chip types of ceramic capacitors and tantalum solid capacitors were quickly developed because their dielectrics are inorganic or metal compounds and have high heat resistance.

Compared to other capacitors, film capacitors have good temperature characteristics, small capacitance changes, and low dielectric loss, as well as stable performance, so small chip-type capacitors have long been in demand. However, the current development is delayed.

The reason for this is that dielectric materials such as polyethylene terephthalate, polystyrene, polypropylene, and polycarbonate have lower heat resistance than the above-mentioned inorganic or metallic compounds, and the soldering temperature is close to their softening or melting points. Particularly in the case of chip-type capacitors, the film undergoes significant shrinkage and melting, resulting in defects such as a decrease in capacitance and insulation resistance, or the capacitor loses its shape.

Therefore, if these films are used as they are to form a capacitor, they will have the above-mentioned drawbacks.

The present invention relates to a chip-type film capacitor using polyethylene terephthalate film as a dielectric, and improves the above-mentioned drawbacks when mounting it on a substrate.

This paper presents a manufacturing method with improved soldering heat resistance, that is, a manufacturing method for capacitors that can be soldered by dipping the capacitor body in molten solder, and has excellent mechanical properties, dimensional stability, chemical stability, etc. It is a heat-resistant capacitor that takes advantage of the characteristics of polyethylene terephthalate film, which also has good electrical properties, and is particularly effective in chip type.

In the present invention, when the capacitor is composed of a metal electrode foil and a dielectric film, the capacitor is coated on one or both sides of the dielectric polyethylene terephthalate, and when the capacitor is composed of two metalized polyethylene terephthalate films, the non-first-come-first-served surface of the metallized film is coated. The capacitor is made using a composite dielectric material with a layer of heat-resistant resin provided by spraying or coding, and then the heat-resistant resin is completely heated and cured at a temperature of 200°C or higher. It is something. The heat curing mentioned here may be carried out in the state of the element after winding or lamination, or may be carried out in the state after being packaged.

As a result of various experiments, such a capacitor can be heated to 270℃10
It was found that it withstood sufficiently even after being immersed in solder for seconds, and its electrical properties such as capacitance, dielectric loss tangent, and cut-off resistance did not change at all. Of course, in a capacitor that uses a normal polyethylene terephthalate film that is not based on the present invention, when immersed in solder, the melting point of the film will be 260°C.
Due to its proximity, the film softens or melts as it shrinks.

Therefore, it is accompanied by a decrease in capacitance and insulation resistance, and sometimes loses its function as a capacitor.

The heat-resistant resin referred to in the present invention uses heat deformation temperature as an evaluation scale,
The heat distortion temperature is 170 when the load per unit area is 18.6 kg/crI according to ASTM D 648 as a measurement method.
Although it is more than 'O, it is particularly effective for resins such as polyamideimide and polyimide.

When a heat-resistant film made of the above-mentioned resin is used as a dielectric, it is expensive and difficult to use on a commercial basis, but in the case of the present invention, in which this solution is applied, it can be done relatively cheaply and with one large 'It is a feature. When coating, it is also possible to coat a wide film, dry it, and then cut it into individual pieces. Alternatively, you can form a capacitor as a long film and then cut it into individual elements. Alternatively, a method may be used in which the coating is applied and dried in a step before winding, and then the coating is continuously rolled.

Next, examples of the present invention will be described. 3 as a first example
A 10% by weight N-methyl-2-pyrrolidone solution of polyimide powder was applied to the non-first-coated side of a μm-thick single-sided aluminum-coated four-layer metallized polyethylene terephthalate film at 100°C for 50 minutes.
Drying was carried out for a minute to form a polyimide film of about 1 μm. An element formed by winding a pair of these films in an overlapping manner, or a chip-type element whose end face was subjected to metal spraying after heat suppression was heated at 200° C. for 3 minutes to cure the applied resin. As a result, those who performed this process,
Even when immersed in a solder bath at 270°C for 10 seconds or more, the durability characteristics did not change at all. In the experimental results,
In this case, the thickness of the coating layer is about 0.8 μm or more,
It was confirmed that it is more effective.

If the bake hardening temperature range was from 200°C to 270°C, it could withstand 270°C, which is close to the upper limit of immersion soldering, for 10 seconds or more. Therefore, when attaching a chip-type film capacitor to a substrate, soldering is now possible without problems such as shrinkage or melting of the dielectric when using solder dipping, flow, or reflow methods.

As a second example, a 10% by weight NN dimethylformamide solution of polyamideimide powder was applied to one side of a 4 μm thick polyethylene terephthalate film, and then 100%
After drying for 3 minutes at ℃, a 1 μm polyamide-imide film was formed and the element was wound alternately with aluminum electrode foil. The element was heated and pressed into a flat shape, and then external electrodes were formed and dried at 200℃. The applied resin was cured by heating for a few minutes. As in the first example, even when immersed in a solder bath at 270° C. for 10 seconds or more, soldering was carried out without any problems, and the characteristics did not change.

The present invention as shown in the first and second embodiments above.

It was confirmed that the same effect is exhibited not only in the case of a capacitor having a structure of metalized films, but also in the case of a capacitor having a structure of a film and a metal electrode foil.

In the present invention, when immersed in a solder bath at 220°C to 230°C, even melted polyethylene terephthalate film capacitors can be coated with the above heat-resistant resin on the base film.
If heat curing treatment is performed at 0° C. or higher, it will be effective in withstanding solder immersion at temperatures exceeding the melting point of polyethylene terephthalate.

A curing temperature of 200° C. or lower for the applied resin is not appropriate because the film will undergo large thermal contraction when immersed in a solder bath, resulting in significant changes in properties.

The temperature should preferably be 200°C or higher, but the practical upper limit is about 270°C, which is the upper limit temperature of a commonly used solder bath.

Note that the above two examples show cases in which the wound element is heated and pressed into a flat shape and then subjected to heat curing treatment at 200°C or higher. The same effect of soldering heat resistance can be obtained even if flattening is performed at the same time as soldering.

It has been confirmed that

As described above, the present invention allows a heat-resistant resin layer with a thickness of about 0.8 μm or more to be attached to a base film without deteriorating the electrical characteristics of a commonly used polyethylene terephthalate film capacitor, and a 200'Q This paper presents a method for manufacturing capacitors at low cost that can sufficiently withstand solder immersion by improving the soldering heat resistance by performing heat curing treatment at the above temperature, especially for chip type capacitors. This invention is considered to be extremely useful and valuable industrially, as it enables stable soldering using the solder immersion method.

Patent applicant: Nissay Electric Co., Ltd. 6

Claims (1)

[Scope of Claims] (11) A film capacitor whose dielectric is a polyethylene terephthalate film formed by winding or laminating dielectric films and metal electrodes such as aluminum foil alternately or by overlapping and laminating single-sided metalized films, At least one side of the dielectric film or one side of the metallized film
A layer of heat-resistant resin is formed on the surface to form a capacitor element.
A method for manufacturing a film capacitor, comprising the step of subjecting the capacitor element to heat curing treatment at 200° C. or higher. (2) Claim No. (2) characterized in that polyamideimide, polyimide, etc. are used as the heat-resistant resin.
1) The method for manufacturing a film capacitor according to claim 1. (3) The method for manufacturing a film capacitor according to claim 1, wherein a heat curing treatment is performed when flattening the element.