Electricity: electrical systems and devices – Safety and protection of systems and devices – Load shunting by fault responsive means
Reexamination Certificate
2000-03-10
2001-09-04
Ballato, Josie (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Load shunting by fault responsive means
C361S091100, C361S111000, C361S118000
Reexamination Certificate
active
06285535
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surge absorber for absorbing surge noise applied on electronic devices.
2. Discussion of the Background
Japanese Examined Patent Publication No. JP-B-63-57918 discloses a surge absorber having a structure in which a conductive ceramic thin film is formed on the surface of an insulating member having a cylindrical shape, a micro-gap is formed to divide the conductive ceramic thin film in the circumferential direction and a total thereof is hermetically sealed in a cylindrical glass in a state where gas is filled at inside thereof. Further, Japanese Unexamined Utility Model Publication No. JU-A-49-80351 proposes a surge absorber in which electrodes each in a shape of a pinnacle having points sharpened toward micro-gaps are formed on an insulating substrate in a flat plate shape.
FIG.
17
and
FIG. 18
show sectional views of conventional surge absorbers.
FIG. 17
shows a surge absorber in a cylindrical shape. Explaining the principle of operating the surge absorber, when surge is applied on a cylindrical surge absorber
40
, arc discharge is caused in a micro-gap
41
and an enclosed gas is successively ionized by the discharge to cause corona discharge by which surge is absorbed.
FIG. 18
shows a surge absorber
42
in a flat plate shape and the principle of operation is basically the same as that of the cylindrical surge absorber.
However, according to the cylindrical one of the conventional surge absorbers, lead wires are extended from central portions of the both ends of the cylinder and therefore, there poses a problem where surface mounting or automatic mounting thereof is difficult. Further, the outer shape is cylindrical and therefore, air-tight cover material other than glass is difficult to use.
Further, according to the one in a flat plate shape, front ends in the micro-gaps are sharpened and accordingly, there poses a problem where the front ends are liable to chip off by discharge when surge is applied with the result of a short life.
SUMMARY OF THE INVENTION
In view of the situation described above, it is an object of the present invention to provide a surge absorber which is easy in surface mounting and is provided with high reliability in respect of repeated discharge.
A first aspect of the present invention is characterized in comprising:
(1) an insulating substrate in a flat plate shape;
(2) a conductive film having a gap in an annular shape and formed in a circular disk shape concentric with the gap on the insulating substrate;
(3) a first electrode arranged at a central portion of the conductive film;
(4) a second electrode in an annular shape concentric with the gap arranged at a peripheral edge portion of the conductive film;
(5) an air-tight crowned member for hermetically sealing the conductive film, the first electrode and the second electrode in a state where a predetermined gas is filled at an inside thereof in cooperation with the insulating substrate;
(6) a first terminal arranged at an outside of the air-tight crowned member for being electrically connected to the first electrode; and
(7) a second terminal arranged at the outside of the air-tight crowned member for being electrically connected to the second electrode.
Here, according to the surge absorber of the present invention, the first electrode and the first terminal may be electrically connected by a through hole formed at a portion of the insulating substrate where the first electrode is arranged, the through hole being penetrated between a surface and a rear face of the insulating substrate and filled with a conductor electrically connected to the first electrode at an inside thereof, and a conductive film formed on the rear face of the insulating substrate for electrically connecting the conductor in the through hole with the first terminal, or the first electrode and the first terminal may be electrically connected by a via hole formed at a portion of the insulating substrate where the first electrode is arranged, the via hole being filled with a conductor electrically connected to the first electrode at an inside thereof, and a conductive layer formed at an inside of the insulating substrate, electrically connected to the first terminal and electrically connected to the conductor at the inside of the via hole at a bottom portion of the via hole, or the surge absorber of the present invention may comprises an insulating film formed on the insulating substrate: the conductive film, the first electrode and the second electrode are formed or arranged on the insulating film; and the first electrode and the first terminal may electrically be connected by a via hole formed at a position of the insulating film where the first electrode is arranged, the via hole being filled with a conductor electrically connected to the first electrode at an inside thereof, and a conductive film formed between the insulating substrate and the insulating film for electrically connecting the conductor at the inside of the via hole with the first terminal.
According to the surge absorber of the present invention, all of the first electrode, the second electrode, the conductive film and the micro-gap are arranged on the same plane above the insulating substrate in a flat plate shape and therefore, the outer configuration can be constituted on the flat plate where surface mounting thereof is facilitated.
Further, since the outer configuration can be a flat plate shape, ceramics material of alumina or the like can be used as the material for the air-tight crowned member.
Further, according to the surge absorber of the present invention, all of the first electrode, the second electrode, the conductive film and the micro-gap are formed on the same plane and in shapes of concentric circles and accordingly, discharge is uniformly caused at a total region of the micro-gap and even when a portion of the conductive film is chipped off by discharge, the discharge start voltage is not variable and reliability in respect of repeated discharge is high.
Further, according to the surge absorber of the present invention, as means for connecting the first electrode arranged at the central portion and the first terminal which serves to connect to outside, for example, the through hole installed at the insulating substrate and the conductive film on the rear face of the substrate, or the via hole installed at the insulating substrate and the conductive layer formed at the inside of the substrate or the via hole installed at the insulating film and the conductive layer below the insulating film can be adopted by which a surge absorber having a structure comprising a small number of parts and yet having high reliability can be realized.
Incidentally, the basic principle of the surge absorber according to the present invention is the same as that disclosed in Japanese Examined Patent Publication No. JP-A-63-57918 mentioned above and therefore, excellent surge absorbing characteristic and high reliability provided to the surge absorber disclosed in the publication are followed as they are.
According to a second aspect of the present invention, there is provided the surge absorber according to the first aspect, wherein the second electrode constitutes the air-tight crowned member.
In this case, the second electrode can be a portion of the air-tight crowned member or can be a total thereof.
By constituting the surge absorber in this way, it can be downsized and an area for mounting thereof to an electric circuit or the like can be reduced compared with the case of the first embodiment.
Further, according to a third aspect of the present invention, there is provided a surge absorber in the first or the second aspect of the present invention, wherein the first terminals are formed respectively at two side faces of the insulating substrate remote from each other and the second terminals are formed respectively on two other side faces of the insulating substrate.
By constituting the surge absorber in this way, as explained later in reference to the drawin
Ballato Josie
Marquis Vaughn
Mitsubishi Materials Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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