JPS5931018A - Method of producing metallized plastic film condenser - 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 relates to a method for manufacturing a metalized polyethylene terephthalate film capacitor, and is aimed at forming a plastic film capacitor into a chip and improving the heat resistance of the plastic film capacitor.

Currently, as electronic devices become smaller, thinner, and more dense,
The electronic components used in these devices are becoming more and more chip-based, and in the field of capacitors, chip-shaped ceramic capacitors, solid electrolytic capacitors, and the like have already been put on the market and have become extremely popular. However, plastic film capacitors have not yet been put into practical use.

The main reason for this is that the dielectric materials currently used in plastic film capacitors are organic polymer compounds such as polyethylene terephthalate, polycarbonate, and polypropylene, whereas the dielectric materials used in ceramic capacitors and tantalum capacitors are inorganic or metallic compounds. This is because it cannot fully satisfy the heat resistance required for chip capacitors during soldering because its heat resistance is lower than that of capacitors. Also, even if there are films with high heat resistance,
At present, it is extremely expensive and it is difficult to reduce the film thickness to 3 μm or less, so small and inexpensive chip capacitors suitable for practical use using this type of film have not become popular. In other words, although a long period of time has passed since various films for capacitors have been provided on the market, the current situation is that chip-type plastic film capacitors have not yet been commercialized.

The present invention uses polyethylene terephthalate film, which is most commonly used in conventional plastic film capacitors, and during the manufacturing process, this film is subjected to a heat treatment characterized by high temperatures and long periods of time, which is different from conventional ones, to significantly improve heat resistance. The present invention aims to reduce the commercialization of chip-type plastic film capacitors by one step if possible, and further improves the soldering heat resistance of conventional lead linear metallized polyethylene terephthalate film capacitors.

The main reason why conventional plastic film capacitors are chip-shaped and cannot satisfy soldering heat resistance is that the melting point of the film is close to the soldering heat resistance test temperature, so the film softens and shrinks significantly during the soldering heat resistance test. As a result, the contact between the vapor-deposited metal on the film and the lead wire end face metal part (metallicon part) processed by metal spraying is impaired, resulting in poor electrical contact, that is, poor dielectric loss or disconnection. This is because this shrinkage causes a significant decrease in capacitance and poor insulation.

The inventors of the present invention focused on the fact that the cause of the above-mentioned defects is the remarkable thermal shrinkage phenomenon of the film at high temperatures of around 250°C,
As a result of various studies on methods for eliminating or mitigating the heat shrinkage phenomenon of this film at high temperatures, it was concluded that heat treatment under appropriate conditions is most effective. That is,
After heat-treating capacitor elements at temperatures between 160 and 200 degrees Celsius for various heating times, heat resistance tests were conducted to investigate electrical properties such as dimensional changes, capacitance, dielectric loss, and insulation resistance of the elements. If heat treatment is performed at each temperature for a predetermined period of time corresponding to that temperature, the heat resistance will be significantly improved, and it will now be possible to place it on a circuit board and pass it through a furnace at around 250 degrees Celsius, which was previously considered impossible. We were able to confirm that it could sufficiently withstand the conditions of reflow soldering.

Furthermore, as a result of measuring the density of the film of the element heat-treated under the various conditions described above, it was found that there is a certain relationship between heat treatment conditions, density, and heat resistance. That is,
If heat treatment is performed while keeping the time constant and changing the temperature, the higher the temperature, the higher the density will become.If the temperature is kept constant and the time is changed, the density will increase as the time gets longer. The higher the density, the better the heat resistance as a capacitor. That is, the density of polyethylene terephthalate film before heat treatment is usually 1.40. ! i'A
I, but when the density was increased by heat treatment, the effect of heat resistance began to appear around 1.405VcII, and it became 1409gA1! The effect becomes even more noticeable from nearby.

The reason for this is considered to be that the heat shrinkage rate of the film has a large relationship with the density.

However, if the temperature is raised in order to increase this density (5), thermal deterioration due to oxidation of the film will occur and the physical strength will decrease, so there is a certain limit to the temperature. In the case of air, the limit is around 200°C, although it also depends on the time. However, in a vacuum, thermal deterioration due to oxidation is suppressed, so the temperature can be raised further.
In addition to thermal deterioration other than oxidation, thermal deformation also begins to occur.
Its limit is around 30℃. If these conditions are combined and the highest heat treatment within a practical range is performed, the density of the film will be 1. It was +2o1/cr&. Therefore, in order to improve the heat resistance of polyethylene terentalate film capacitors, the density of the film must be 1.4.
05-1420. ! Heat treatment may be performed within the range of i'/ffl depending on the purpose. In other words, the density is 1.405V for the soldering heat resistance of the conventional lead wire type.
A density of 1.40 (1/i or higher) is effective for the soldering heat resistance of chip-shaped products.

The above-mentioned density value is the density of only the film after removing the weight of the vapor-deposited metal 6) from the density value obtained by cutting a minute piece from the capacitor element and measuring it as a sample. The weight of the deposited metal is determined by first calculating the thickness of the deposited film from the resistance value of the deposited film, and then multiplying the thickness of the deposited film by the specific gravity of the deposited metal.

Conventionally, in manufacturing capacitors, heating a capacitor element or semi-finished product at a certain temperature for several hours, called heat treatment, is a widely used method. However, in this case, the purpose is to dry the device, relax local stress remaining inside the device, and stabilize molecular bonds within the film, and is generally carried out at a temperature in the range of 100 to 150°C.

On the other hand, the purpose of the heat treatment in the present invention is to increase the density of the film and improve its heat resistance, which is completely different from the conventional purpose as described above, and the heat treatment conditions are also 160°C or higher. It requires a long time and is a completely new manufacturing method that has not been used before.

By the way, to give a specific example, the density at 160℃ is 1.405
To make it 11/cd or more, the density is 1.4 or more for 50 hours or more.
At a temperature of 200 (7) °C, it takes more than 2 hours to achieve a density of 1.405. ! It takes 5 hours or more for il/d or more.

Further, in the case of the above-mentioned heat treatment, it is not necessary to perform it at a single temperature, but the same purpose can be achieved by performing the heat treatment at a low temperature for a long time and at a high temperature for a short time in combination. Therefore, when actually setting heat treatment conditions, it is only necessary to combine the optimal temperature, time, atmospheric pressure, or degree of vacuum within the capacity of the manufacturing equipment so as to obtain a density that corresponds to the required heat resistance. become. More preferably, the density is 1.409
When the value is 11/cII1 or higher, more favorable results than conventional characteristics can be obtained in terms of electrical characteristics, and therefore, consideration is given to improving the characteristics of the capacitor. It was confirmed that the capacitance-temperature characteristics and dielectric loss-temperature characteristics were significantly improved compared to conventional values. Figures 1 and 2 illustrate this.

Hereinafter, a specific embodiment of the present invention will be described with reference to the drawings. Fig. 3 is a developed perspective view of a device wound with a pair of single-sided aluminum vapor-deposited polyethylene terephthalate films (8) each having a thickness of 3 μm and a width of 4.5 mm. In this case, the metallized polyethylene terephthalate film is shifted by 0.5 ig in order to obtain good contact during metal spraying, so-called flat l-wrap. 1 shows the wound element body and the winding width shifted by 2 degrees. Approximately 130 to 150 after winding these elements
FIG. 4 shows a state in which the element was heated and compressed for several minutes at .degree. C. to form a flat shape, and a metal such as solder was sprayed on both end surfaces to provide metallic contact portions on the end surfaces of the element. 3 is a flat shaped element, 4
shows the metal sprayed metal part. This sample is heat treated at 200°G for 10 hours in a constant temperature bath. 5 in FIG. 5 is a metal plate bent at the external electrode and attached to the metallic contact portion 4 by spot welding (not shown), as shown in FIG. In FIG. 7, the outer periphery of this sample is coated with a covering by molding with epoxy resin, which is indicated by 6. Here, the external electrode 5 is cut to an appropriate length and bent along the exterior to complete the chip-type capacitor 7 as shown in FIG. 8 is the completed external electrode.

Although the heat treatment step (g) was carried out after the metal spraying on the upper side, it may be carried out before the metal spraying or after the coating and exterior processing. Further, in order to improve moisture resistance, the element before being coated or the product after being coated may be impregnated with wax.

As shown in FIG. 9, the chip-type capacitor completed in this way is shown in the conductive portion 11.1 of the printed circuit board for heat resistance testing.
2. After applying solder paste (not shown), place it at the dotted line position 15 and preheat it in a hot air heating furnace for 150605 minutes, then heat it at 250°C for 90 seconds to reflow solder it to the printed circuit board. No abnormalities were observed in the characteristic values. Figure (10) Next, a similar sample was made and a high temperature life test was conducted by applying a DC voltage of 125 V in a constant temperature bath at 85°C. As shown in FIG. 10, the results showed normal trends in insulation resistance, capacitance, and dielectric loss, and it was confirmed that there were no practical problems. Although the example shows an example of a capacitor using a metalized film on one side, a chip type capacitor using a metalized film on both sides and a non-metalized film, both of which are made of polyethylene tere-7 talate, has similar characteristics. This has been confirmed. FIG. 11 is an external view of a metallized plastic film capacitor using a lead-shaped polyethylene terephthalate film, where 9 is a resin-sheathed main body and 10 is a lead wire. The present invention can be applied to this conventional capacitor as described above to improve the soldering heat resistance.

As described above, the present invention uses polyethylene terephthalate film, which has conventionally been used in large quantities, and heat-treats the film to a predetermined density during the manufacturing process. It is possible to obtain a capacitor, and at the same time, it is possible to improve the soldering heat resistance of a conventional lead-shaped metallized polyethylene terephthalate capacitor, and the industrial effects of the present invention are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a characteristic comparison diagram of the capacitance change rate versus temperature characteristic, and FIG. 2 is a characteristic comparison diagram of the conventional plastic film capacitor and the chip type plastic film capacitor according to the present invention regarding the dielectric loss versus temperature characteristic. FIG. 3 is a developed view of a device wound with a single-sided metallized plastic film capacitor according to an embodiment of the present invention. FIG. 4 is a perspective view of the element shown in FIG. 3 which has been shaped into a flat shape and is provided with a metallic contact portion by metal spraying. FIG. 5 is a perspective view of a metal plate serving as an external electrode, and FIG. 6 is a front view of the element shown in FIG. 4 with spot welding of the external electrode (spot welding is not shown). FIG. 7 is a front view of the structure shown in FIG. 6, which is coated with resin and molded. Figure 8 shows a completed chip-type plastic film capacitor (12) of the present invention. FIG. 9 is a plan view showing how a chip-type plastic film capacitor is assembled into a test printed circuit board. Fig. 10 is a graph of the data of the high temperature life test, and Fig. 11 is a perspective view of a gold-metalized polyethylene terephthalate film capacitor with mm leads. l...Film capacitor element body 2...
Shifting winding width 3... Flat shaped element body
4...Curved metal contact portion 5...External electrode plate
6... Resin-coated chip capacitor body 7.
...Chip capacitor (finished product) 8...
・・External electrode 9・・・・Lead linear resin exterior metallized polyethylene tele-7 talate film capacitor body
10...Lead wire 11.12...
・Conductive part of printed circuit board 13.14...Measurement lead wire terminal 15...Chip type capacitor mounting position γ/Steel-40-2002040608111100-111 Temperature ("C) Po31 8 Oyu, A; f7rA Saiko 12 λ?14 Hand pot 1 correction t (vigilante) 250 500 10
00 hours (H) 250 500 1000
Time (I() 250 500 1000
Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office, Indication of the case: Japanese Patent Application No. 57-140951, Title of the invention: Person who corrects metallized plastic film capacitors Relationship with the ° 1-3-18 Name Nissay Denki Co., Ltd. Contents of the agent's amendment There was a mistake in some of the symbols in Figure 10 of the drawings attached to the specification of this application, so the corrected Figure 10 is as attached. I'll submit it. (1)

Claims (2)

[Claims] (1) In a plastic film capacitor formed by winding or laminating single-sided metalized films or double-sided metalized films and non-metalized films, polyethylene terephthalate is used for the metalized film and the non-metalized film, and the manufacturing process thereof , the density of the polyethylene terephthalate film is 1.405 to 1.420.
A method for manufacturing a metallized plastic film capacitor 0, characterized by comprising a step of heat treatment until the g/Cd range is reached. (2) The method for manufacturing a metallized plastic film capacitor according to claim 1, wherein the heat treatment is performed in air, reduced pressure, or vacuum.