JPH03293709A - Chip type film capacitor - Google Patents

Abstract

PURPOSE:To realize miniaturization and capacity enlargement and get heat resistance by using a polymer alloy film comprising polyketone sulfide and other thermoplastic resin as a dielectric layer. CONSTITUTION:A film 2 consisting of polymer alloy of polyketone sulfide and thermoplastic resin is used for a dielectric. And electrodes 4 are formed at both faces of the polymer alloy film 2, and this is rolled to form a capacitor element 1, and the electrode 4 of the capacitor element 1 and the external terminal for surface mounting are connected electrically with each other. That it, the one, which is made polymer alloy by blending thermoplastic resin easy to film to the polyketone sulfide high in heat resistance and high in dielectric constant, is made into a film. Hereby, the dielectric of a capacitor, which is excellent in heat resistance and is high in dielectric constant and is made into a film, can be obtained.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a chip-type film capacitor used for surface mounting, etc., which requires miniaturization and heat resistance.

[Conventional technology]

Film capacitors are made by rolling out a film.1. f, - Using plastic as a dielectric, electrodes are formed on both sides of this dielectric film by metallization treatment, etc., and are wound or layered to form a capacitor element, and the electrodes are electrically connected to external electrodes by metallization treatment, etc. It is obtained by connecting and further applying an exterior means such as a resin exterior. In recent years, electronic components are mounted by placing the electronic components at predetermined positions on a printed wiring board and soldering them using a method such as a reflow solder method, a wave solder method, or a dip solder method. In any case, when electronic components are soldered to a printed wiring board,
It will be exposed to a high temperature of about 260°C for several seconds to several tens of seconds. For this reason, solder heat resistance is required as an essential characteristic of chip-type electronic components. Further, in order to miniaturize electronic devices, higher packaging density of electronic components is required, and the need to mount a large number of electronic components on a printed wiring board requires miniaturization of electronic components as well. Resin films such as polyethylene, polystyrene, polycarbonate, polyethylene terephthalate, and polyphenylene sulfide have conventionally been used as dielectrics for film capacitors. However, these conventional materials have melting points that are comparable to or lower than the melting temperature of solder. Thermoplastic resin films such as polyethylene terephthalate mopolyphenylene sulfide have a relatively high melting point and are suitable for heat-resistant applications. However, when these materials are used alone, the film begins to soften before it reaches its melting point, so even if measures such as making the exterior material sufficiently thick to prevent heat conduction are taken, The temperature was only 150°C at most, making it difficult to use it for surface mounting under the same conditions as other electronic components. Therefore, recently, polyimide resin films, which have a high melting point and are heat resistant, are being considered. This resin is suitable as a dielectric material due to its high melting point and heat resistance, but it is difficult to process due to the material's low dielectric constant and mechanical properties, making it difficult to process into thin films. in,
The drawback was that it was difficult to miniaturize the capacitor. For example, Japanese Patent Application Laid-Open No. 1999
As in Japanese Patent No. 253907, a dielectric layer using a polyketone sulfide film has been proposed. Polyketone sulfide has a high heat resistance, excellent mechanical strength, and a high dielectric constant, so that small chip capacitors that are resistant to soldering heat can be obtained.

[Problem to be solved by the invention]

As mentioned above, polyketone sulfide has excellent properties as a dielectric material for chip-type capacitors, and it is possible to produce a considerably thin film, but the film thickness that can be processed is limited to about 2 μm. For this reason, it has not been possible to sufficiently meet the objective of obtaining higher capacitance by making the dielectric film thinner and bringing the electrodes closer together. The present invention improves these drawbacks of conventional film capacitors, and aims to provide a chip-type film capacitor that can be further miniaturized, has a larger capacity, and has heat resistance.

[Means to solve the problem]

The chip-type film capacitor of this invention has a dielectric material including:
Using a film made of a polymer alloy of polyketone sulfide and thermoplastic resin, which has heat resistance to molten solder temperature and can be miniaturized, electrodes are formed on both sides of this polymer alloy film, and the film is rolled or layered. A capacitor element is formed using a capacitor element, and means for electrically connecting the electrodes of the capacitor element and an external terminal for surface mounting is provided, and if necessary, an exterior means is provided. Furthermore, this invention is characterized in that polyphenylene sulfide or polyethylene terephthalate is selected as the thermoplastic resin that forms the polymer alloy with polyketone sulfide.

[For production]

Polymer alloy means a multi-component composite material containing two or more types of polymers. The form of the polymer alloy takes the form of a copolymer such as block copolymerization or graft copolymerization, a physical blend, a chemical blend, and a polymer complex. Both were combined 2
More than one type of polymer can exhibit its own unique characteristics, and can also complement each other's shortcomings to exhibit excellent characteristics for specific purposes. The polyketone sulfide used in this invention can be made into a film at a heat deformation temperature of 340° C. to 350° C. or higher. It also has high mechanical properties such as tensile strength, so the film is less likely to be cut or stretched during winding of capacitor elements. Also, looking at the dielectric constant, which is important for capacitors,
While other resins conventionally used in film capacitors, such as polyphenylene sulfide and polyethylene terephthalate, have a dielectric constant of about 3 at most, polyketone sulfide has a dielectric constant of 4 or more. can get. However, polyketone sulfide film is difficult to make into a thin film, and thin films cannot be obtained, whereas thermoplastic resins such as polyphenylene sulfide and polyethylene terephthalate are easy to make into thin films, and polyethylene terephthalate in particular can be made into extremely thin films of 1 μm or less. is obtained. Therefore, in this invention, by blending polyketone sulfide with a thermoplastic resin such as polyphenylene sulfide or polyethylene terephthalate to form a polymer alloy into a film, it has excellent heat resistance, a high dielectric constant, and a thin film. A dielectric material of a capacitor is obtained. In this case, the polymer alloyed film shows a decrease in heat resistance and dielectric constant compared to polyketone sulfide alone, but its heat resistance is within the range that can withstand the temperature rise caused by immersion in molten solder for a predetermined period of time. The blending of the polymer alloy may be determined within a range in which both the factors of increase in capacitance due to reduction in film thickness and decrease in capacitance due to decrease in dielectric constant are offset. The preferred blending ratio varies depending on the selection of materials used and the required specifications, but if the blending ratio of one material is significantly large, the exclusive characteristics of that material will become stronger (and the desired effect of this invention will not be fully achieved). Therefore, the preferred blending ratio of both materials is in the range of 3:1 to 1:3.

[Examples] Hereinafter, the chip-type film capacitor of the present invention will be described in detail according to examples. FIG. 1 is an exploded perspective view showing the structure of a typical capacitor element 1 of the present invention. In the figure, metals such as zinc and aluminum are deposited on one surface of a polymer alloy film 2 made of a strip of polyketone sulfide and a thermoplastic resin, leaving an untreated strip 3 at the edge of the film. It is formed as an electrode 4. Then, the capacitor element 1 is formed by overlapping and winding the two strip-shaped polymer alloy films 2 that have undergone these treatments so that the untreated portions 3 are located in opposite directions. At this time, the electrodes 4 formed on the two strip-shaped polymer alloy films 2 by vapor deposition are exposed at both winding end faces of the capacitor element 1. FIG. 2 is a cross-sectional view showing the exterior state of the chip-type film capacitor of the present invention housing the capacitor element 1, and the electrodes 4 exposed on the winding end faces on both sides of the capacitor element 1 are treated with metallized or conductive. It is connected to one end of a surface-mountable plate-shaped external terminal 6 by an electrical connection means 5 such as an adhesive side. Parts of the capacitor element 1, the electrical connection means 5, and the external terminals 6 are covered with an exterior 7 made of an exterior material such as a heat-resistant thermosetting resin. Furthermore, exterior 7
The external terminal 6 protruding from the side surface is bent into a substantially U-shape along the bottom surface from the side surface of the exterior 7, so that it can be surface mounted when placed on a printed wiring board. In this example, a capacitor element was formed by overlapping and winding metal electrodes formed on the surface of a dielectric film by vapor deposition, but the capacitor of the present invention is not limited to this structure. They may be stacked in a layered manner instead of being rolled. Further, the electrode may be formed by overlapping a dielectric film and a foil-like metal electrode to form a capacitor element. Regarding the connection between the capacitor element and the external electrode, a lead may be drawn out from the electrode portion and connected to the external terminal by means such as welding, without using metallicon treatment or conductive resin. It goes without saying that the shape of the external terminal and the packaging method are not limited to those of this embodiment as long as they are suitable for the purpose of surface mounting. Next, we will show an experimental example in which a polymer alloy film was created and its characteristics were investigated, and an electrode was formed on the surface of the film to create a capacitor for evaluation and the characteristics were compared. First, as an example of this invention, polyketone sulfide (PK
A thin film that can be made from a polymer alloy obtained by blending S) with predetermined amounts of polyphenylene sulfide (PPS) and polyethylene terephthalate (PET) was created. For comparison, we also created films of the single resins that make up the polymer alloy, and examined their heat resistance, thin film formation limits, and dielectric constants. Regarding heat resistance, which is one of the objectives of this invention, the required heat resistance condition is a temperature of 230°C to 260°C for 10 seconds to 30 seconds per hour. Therefore, these samples were immersed in a molten solder bath at 260°C for 30 seconds to examine changes. Regarding film thinning, the limits for forming a film that is free from pinholes and has the tensile strength required for capacitor element forming equipment was investigated. We also investigated the dielectric constant of each composition. The results are shown in Tables 1 (a) and (b). 1-TABLE ABOVE (a) PPS/PKS Polymer Blend (b) PET/PKS Polymer Blend △ *1 ○ at 215 seconds, × at 30 seconds. Next, these films were used as dielectrics, and aluminum layers having a thickness of about 10 mm were vacuum-deposited on both sides of the films as electrodes. The area of this electrode is 2 cm
It has an area of 2 C1n, or 4cIII. Then, a metal lead was electrically connected to the surface of the vapor-deposited electrode using a conductive adhesive to complete a flat plate-shaped capacitor for evaluation. Table 2 shows the results of investigating the capacitance and loss of these capacitors. (Measured by applying a bias voltage of 30μ) As can be seen from this result, capacitors using polyketone sulfide film have a high dielectric constant, but because it is difficult to make the film thin, Although the dielectric constant is inferior, a higher capacitance cannot be obtained compared to capacitors made with these thermoplastic resin films, which can be formed into thinner films. On the other hand, although thermoplastic resin films can provide high capacitance, they lack heat resistance, which is essential for chip-type capacitors. On the other hand, a capacitor using the polymer alloy of this invention as a film material can meet the requirements of both heat resistance and high capacitance, and is suitable as a surface-mountable chip type capacitor, which is the purpose of this invention. I know what you're doing. [Effects of the Invention] As described above, the chip-type film capacitor of the present invention has the following features: (1) The dielectric constant of the polymer alloy film of polyketone sulfide and thermoplastic resin is higher than that of other heat-resistant resin films; Therefore, the capacitance per unit volume can be increased, and the capacitor can be made smaller. (2) Polymer alloy films of polyketone sulfide and thermoplastic resin can be formed into extremely thin films of about 1 μm or less, as the blended thermoplastic resin can generally be made into thin films, and have mechanical properties such as tensile strength. Since the capacitor has excellent properties, it is possible to manufacture small-sized, large-capacity capacitor elements. (3) Since the tensile strength is high and tension can be applied to the film, when winding the film while applying tension to it, as in the case of wound-wound capacitor elements, the element is firm and can be wound stably. Vibration is prevented and electrical characteristics are stabilized. Furthermore, there is no inconvenience such as cutting the film during winding work, and productivity is improved. (4) The polymer alloy film of polyketone sulfide and thermoplastic resin has a high heat resistance, so even if it is exposed to the high temperature of molten solder for a certain period of time when soldering to a printed wiring board, the dielectric film will not deteriorate. No deformation. These effects make it suitable for chip-type film capacitors, which require small size, large capacity, and heat resistance.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing the element structure of the chip-type film capacitor of the present invention. FIG. 2 is a sectional view showing a completed chip-type film capacitor of the present invention using the capacitor element shown in FIG. 1. 1. Capacitor element, 2. Polymer alloy film, 3. Untreated portion, 4. Electrode, 5. Electrical connection means, 6. External terminal, 7. Exterior.

Claims (2)

[Claims] (1) Using a polymer alloy film made of polyketone sulfide and other thermoplastic resin as the dielectric layer, electrodes are arranged on both sides of this polymer alloy film,
It is characterized by comprising a capacitor element formed by winding or layering, an external terminal for surface mount, and means for electrically connecting the electrode of this capacitor element and the external terminal for surface mount. Chip type film capacitor. (2) The chip-type film capacitor according to claim 1, which is a polymer alloy using either polyphenylene sulfide or polyethylene terephthalate as the thermoplastic resin.