Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Patent
1986-02-04
1987-06-09
Griffin, Donald A.
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
H01G 408
Patent
active
046725067
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
Technical Field
This invention relates to a capacitor, and more particularly, a capacitor in which the dielectric material comprises a plastic film.
Heretofore, it is known for example in Japanese patent application Kokai publication No. 57-187327 that a capacitor excellent in frequency characteristics, temperature characteristics and soldering resistance can be obtained by using a biaxially oriented polyphenylene sulfide film as the dielectric material of the capacitor.
A capacitor in which the dielectric material comprises a heat-resistant film such as a polyimide film or an aromatic polyamide film is also known.
Because of its excellent electrical characteristics, such a capacitor in which the dielectric material comprises a plastic film, the so-called film capacitor, is frequently used in circuits which require precision, such as a time constant circuit.
However, such a conventional capacitor, especially one having a thin dielectric material has a defect that its capacitance and breakdown voltage disperse widely.
Further, in recent years, in order to reduce the size of a circuit and to improve an efficiency of packaging, it is necessary to fabricate a film capacitor in chip form.
However, on mounting a capacitor in chip form (hereinafter, referred to as a chip capacitor), it must be directly fixed on a circuit substrate by, for example, dipping it in a soldering bath and so the whole capacitor is exposed to a high temperature. Thus it is impossible to fabricate an ordinary capacitor in which the dielectric material comprises polyester, polypropylene, polycarbonate, polystyrene or the like in chip form because, even when it is equipped with a thick outer package, it is lacking in heat resistance and it undergoes a marked change in capacitance, loss of insulation resistance, poor connection, etc. during packaging.
On the other hand, when a polyimide film, an aromatic polyamide film or the like is used as a dielectric material, it is possible in respect of soldering-heat resistance to fabricate the capacitor in chip form, but such a capacitor shows poor electrical characteristics and has limited usefulness as a film capacitor.
Accordingly, the use of a biaxially oriented polyphenylene sulfide film as a dielectric material was proposed to realize both desirable electrical characteristics and soldering resistance. However, such a capacitor is not satisfactory in respect of soldering resistance in fabricating in chip form unless the periphery of its element is covered with a thick outer package and, if this is done, its outer size increases, which is contradictory to the aim of reducing the size of a circuit by fabricating the capacitor in chip form.
It is an object of this invention to provide a capacitor which has small dispersions of capacitance and breakdown voltage, satisfies both of electrical characteristics and soldering resistance on higher levels and shows remarkably excellent characteristics as a chip capacitor by eliminating the above-mentioned defects of a conventional capacitor.
DISCLOSURE OF THE INVENTION
Therefore, this invention provides a capacitor in which the dielectric material comprises a biaxially oriented polyphenylene sulfide film comprising a resin composition mainly consisting of poly-p-phenylene sulfide and having a small-protrusion density on the surface in the range of from 20 to 300/mm and a large-protrusion density on the surface in the range of 5/mm or below, and the electrodes comprise thin layers or foils of a metal.
As a result, the capacitor of this invention has excellent characteristics, which have not been realized in any conventional film capacitor, that it is excellent in the stability and uniformity of capacitance and breakdown voltage and that it can be mounted as a chip capacitor on a substrate by a surface mounting process without any limitation by using a usual soldering apparatus under usual conditions with only little changes in capacitance, suppressed lowering in insulation resistance and withstand voltage, etc.
BRIEF DESCRIPTION OF THE D
REFERENCES:
patent: 2819492 (1958-01-01), Cummin et al.
patent: 3430116 (1969-02-01), Johnstone
patent: 3585468 (1971-06-01), Chertok et al.
patent: 4130722 (1978-12-01), Levijoki
patent: 4367511 (1983-01-01), Crass et al.
patent: 4458294 (1984-07-01), Womack
patent: 4527219 (1985-07-01), Johnson et al.
patent: 4578737 (1986-03-01), Westermann
Deguchi Yukichi
Kobayashi Hiroaki
Griffin Donald A.
Toray Industries Inc.
LandOfFree
Capacitor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Capacitor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Capacitor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1833241