JPH03241806A - Chip type metallized film capacitor - Google Patents

Abstract

PURPOSE:To alleviate the deterioration by heat of a high molecular dielectric film, to satisfy heat-resisting characteristics when a surface-mounting reflow treatment is conducted, to improve potential inclination, and to make it possible to miniaturize the title film capacitor by a method wherein a high molecular dielectric film, having the specific value or lower of average surface roughness on both surfaces, is used. CONSTITUTION:In a chip type metallized film capacitor formed by winding or laminating a metallized film having a vapor-deposited metal 7 on one side or both sides of a high molecular dielectric film 6, a high molecular dielectric film 6, having the average surface roughness on both surfaces of 0.04mum or less, is used. For example, polyethylene naphthalate film, having average surface roughness of 0.04mum or less, is used as the high molecular dielectric film 6, and a metallized plastic film is obtained by forming an aluminum thin film metal 5 on the surface of the above-mentioned film 6. The metallized plastic film is laminated, and after an external electrode 8 has been formed by conducting a metal flame-spraying operation, a heat-treatment process is finished, solder-plating 9 is provided on top of the external electrode 8, and a simple outer covering is provided by coating ultraviolet-ray-hardening resin 10 on the laminated cut surface.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a chip-shaped metallized film capacitor used in electronic and electrical equipment.

Conventional technology In recent years, electronics technology has made remarkable progress, and electrical equipment using electronics technology2 communication equipment, IIJi
[Equipments are becoming more multi-functional and smaller. Therefore, in promoting miniaturization of these devices, there is a strong demand for miniaturization of passive components to form circuits.

A typical example of this is the chipping of passive components such as resistors, capacitors, and coils. In addition, as passive components have been made into chips, the method for mounting components on printed circuit boards constituting circuits has also shifted to a surface mounting method that allows for higher density mounting than before. In this method, parts are fixed to one or both sides of a board with adhesive or cream solder, and soldered by passing them through a solder bath or high-temperature furnace (hereinafter abbreviated as surface mount reflow).Therefore, The component body is directly exposed to high temperatures, and the temperature applied to the component body is much higher than that of a conventional leaded component in which only the lead wire is immersed in a soldering bath.For example, in the case of a film capacitor, a conventional leaded component with only the lead wire immersed in the solder bath. While the internal temperature of the capacitor during soldering is 100 to 130℃,
The internal temperature of chip film capacitor is 210~240℃
℃, which is about 100℃ higher. In addition, in order to miniaturize devices, methods are used to reduce the space inside the device and increase the density of the board structure, so when using the device, heat generated by active electronic components (ICs, transistors, diodes, etc.) is kept inside the device. It becomes muffled and the temperature rises.

As described above, the usage conditions for chip components are much more severe in terms of temperature than for conventional leaded components.

Conventionally, film capacitors use polyethylene terephthalate (hereinafter abbreviated as PET) as a dielectric material.

Films such as polypropylene (hereinafter abbreviated as PP) were used, but they had problems in terms of heat resistance, and polyphenylene sulfide film (hereinafter abbreviated as PPS) was developed as a new heat-resistant dielectric film. Naphthalate (hereinafter referred to as PEN) has been attracting attention and being used.

A conventional chip capacitor will be described below with reference to the drawings.

FIG. 4 is a configuration diagram of a moldless type chip film capacitor. A thin metal film 2 such as aluminum is formed on the surface of the dielectric film 1 to form a metallized plastic film, the metallized plastic film is laminated, and an external electrode 3 for drawing out the electrode from the internal electrode is formed by metal spraying. After that, through a heat treatment process at high temperature, solder plating 4 is provided on the top of the external electrode, and a simple exterior coated with ultraviolet curable resin 5 is applied to the cut surface to form a moldless type chip film. I'm getting a capacitor.

In FIG. 4, the dielectric film 1 is constructed by increasing the average surface roughness on both surfaces.

In general, polymer dielectric films are
It causes contraction and thermal changes over time. In particular, for chip film capacitors that are exposed to high temperatures during surface mount reflow, in order to suppress shrinkage of the polymer dielectric film due to high heat, a high temperature heat treatment step is provided in the manufacturing process to suppress thermal element deformation during high temperature mounting. It is characterized by its heat resistance properties. Generally speaking, it is a well-known fact that a polymer dielectric film that has been heat-treated at a certain temperature will have a very small degree of shrinkage at temperatures within that range, as long as the processing temperature is not exceeded. It is. Therefore, the temperature in the heat treatment step is set to the mounting reflow temperature or higher.

Problems to be Solved by the Invention However, in the case of chip film capacitors, many problems have arisen due to the polymer dielectric film.

Among these issues, one of the major issues is whether heat treatment is applied during the manufacturing process of chip film capacitors in order to eliminate the thermal shrinkage of polymer dielectric films during surface mount reflow. Polymer dielectric films undergo thermal deterioration, significantly reducing the level of withstand voltage characteristics. Therefore, in order to ensure heat resistance, the potential gradient (withstand voltage per micron unit) is reduced, resulting in an increase in the size of the device.

In line with the recent miniaturization of equipment, chip film capacitors are also becoming increasingly smaller, and this has become a major drawback for chip film capacitors that require heat resistance characteristics.

To address these issues, particularly for chip film capacitors, various proposals have been made to ensure heat resistance and improve withstand voltage characteristics, but most of them involve methods for exterior coating of capacitor elements, heat-resistant electrode structures, This is a consideration regarding the insertion of heat-resistant plates.

However, it is impossible to completely prevent temperature from passing through the inside of the element, and if an arbitrary heat treatment is performed and the temperature is higher than that, it is impossible to suppress the thermal shrinkage of the polymer dielectric film itself due to the high temperature. This is extremely difficult, and ensuring heat resistance and improving withstand voltage characteristics are extremely demanding requirements for chip film capacitors.

Means for Solving the Problems In order to solve the above problems, the chip-type metallized film capacitor of the present invention has an average surface roughness of 0.04 on both surfaces.
It is characterized by using a polymeric dielectric film having a diameter of μm or less.

Regarding the difference in surface roughness of the working polymer dielectric film, the larger the surface roughness, the weaker the adhesion, and the flatter the surface, the better and stronger the adhesion.

Conventionally, capacitor characteristics due to these differences were mainly determined by
Taking advantage of the adhesion of a polymer dielectric film with a flat surface roughness, it prevents moisture from entering and improves moisture resistance. The effect of suppressing oxidation, which causes the electrode to lose its function and cause a change in capacitance, has been attracting attention. However, little attention has been paid to the study of heat resistance characteristics due to differences in surface roughness of polymer dielectric films.

As a result of intensive research, the inventors succeeded in lowering the temperature of the heat treatment process required during the manufacturing process of chip film capacitors by using a polymer dielectric film with a smaller surface roughness on both surfaces. It has been found that by pressing the film, thermal deterioration of the polymer dielectric film can be alleviated, the potential gradient can be improved, and the desired heat resistance properties can be satisfied.

The reason for this is that a polymer dielectric film with a smaller surface roughness has a higher surface roughness than a polymer dielectric film with a larger surface roughness, even when subjected to high temperature heat treatment under the same conditions. It has been discovered that the interlayer adhesion becomes strong, which has the effect of mutually suppressing the shrinkage of the dielectric film itself due to heat, and the heat resistance properties are dramatically improved.

As a polymer dielectric film, the surface roughness of both surfaces is 0.
By using a flat material with a diameter of 0.4 μm or less,
It is possible to significantly improve the potential gradient and realize a smaller chip film capacitor. In particular, PPS film and PE film of polymeric dielectric film corresponding to heat resistance.
By using N film, it is possible to achieve even higher heat resistance characteristics for surface mounting reflow at higher temperatures, and furthermore, it is possible to promote miniaturization.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a moldless type chip film capacitor in one embodiment of the present invention.

As the polymer dielectric film 6, P with a thickness of 3.5 μm is used.
EN film was used. A thin metal film 5 of aluminum is formed on the surface of this PEN film 4 to form a metallized plastic film, the metallized plastic film is laminated, and an external electrode 8 for drawing out the electrode from the internal electrode is formed by metal spraying. After that, through a process of heat treatment at high temperature, solder plating 9 is provided on the top of the external electrode, and a simple exterior coated with ultraviolet curable resin 10 is applied to the laminated cut surface, resulting in a moldless type chip film. Get a capacitor.

In particular, in order to ensure heat resistance during surface mounting reflow of chip film capacitors, a heat treatment process at high temperature is provided during the above manufacturing process.

At this time, the average surface roughness of both surfaces of the PEN film 4 used is 0.04 μm or less, which satisfies the desired heat resistance properties and improves the withstand voltage properties.

The operation of the capacitor configured according to the present invention will be explained with reference to the drawings.

Figure 2 shows the average surface roughness of the PEN 3.5μm film as 0.
．． The potential gradient (withstand voltage per micron unit) results obtained by high temperature load life test are shown for three types: 08 ttm, 0.04 μm, and 0.01 μm. The vertical axis represents the potential gradient, and the horizontal axis represents the heat treatment temperature performed during the manufacturing process. The test conditions are that a DC voltage is continuously applied in an air atmosphere at a temperature of 105° C., and after 1000 hours, the test is passed if the initial capacitance is ±5% and the insulation resistance is 1X10IOΩ. As can be seen from FIG. 2, irrespective of the average surface roughness of the film, as the heat treatment temperature increases, the potential gradient decreases due to thermal deterioration of the dielectric film. Figure 3 shows temperatures at 220°C and 240°C during the heat treatment process during the manufacturing process.

The surface mounting reflow test results are shown when heat treatment was performed at 260° C. for 5 hours each. The vertical axis represents the guaranteed temperature for surface mounting reflow heat resistance, and the horizontal axis represents the average surface roughness of the PEN film. The test conditions were that the sample was allowed to absorb 4% of its initial capacity in an atmosphere at a temperature of 85°C and a humidity of 95% (corresponding to the rate of change in capacity throughout the year when a PEN film was used as a capacitor), and then at a maximum temperature of 200°C. ℃～280
After being held in an atmosphere at ℃ for 1 minute, the case where there is no appearance defect (dimensional change in 2 cracks) and the capacitance after moisture absorption satisfies within ±5% is considered to be a pass, and the heat resistance is guaranteed.From Figure 3. As can be seen, the average surface roughness of the film is 0.04 μm
As the surface mounting reflow temperature increases, the guaranteed heat resistance temperature decreases, and when the average surface roughness becomes 0.04 μm or less, the guaranteed heat resistance temperature increases. When the average surface roughness is 0.04 μm or less, the interlayer adhesion between dielectric films becomes strong,
This mutually suppresses shrinkage of the dielectric film itself due to heat.

From the above, it is understood that the average surface roughness of both surfaces of the polymer dielectric film needs to be set to 0.04 μm or less in order to consider the heat resistance characteristics and improve the potential gradient during surface mounting reflow. Ru.

Effects of the Invention As is clear from the above results, the chip film capacitor of the present invention has excellent heat resistance during surface mounting reflow by using a flat polymer dielectric film with an average surface roughness of 0.04 μm or less on both surfaces. It satisfies the characteristics, dramatically improves the potential gradient, and enables significant downsizing.

Therefore, it can greatly contribute to the miniaturization of electronic devices and electrical devices, and has a very large effect on industry.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a moldless type chip film capacitor according to an embodiment of the present invention, FIG.
FIG. 3 is a characteristic diagram of the chip capacitor of the present invention, and FIG. 4 is a partially cutaway perspective view of a conventional moldless type chip film capacitor. 6... Polymer dielectric film, 7...
Vapor deposited metal, 8... External electrode, 9... Solder plating electrode, 10... Simple exterior.

Claims (2)

[Claims] (1) In a chip-type metallized film capacitor formed by winding or laminating a metallized film formed by forming vapor-deposited metal on one or both sides of a polymeric dielectric film, the average surface roughness of both surfaces is 0.04 μm. A chip-shaped metallized film capacitor characterized by using the following polymeric dielectric film. (2) The chip-shaped metallized film capacitor according to claim 1, wherein a polyethylene naphthalate film is used as the polymeric dielectric film.