Murata Manufacturing Co., Ltd.

Yoshiaki Abe

Toshiharu Hirota

Takahiko Kawahara

Yutaka Ikeda

Takayo Katsuki

Yasuhiro Nabika

Hiroshi Ibaragi

Kazuto Miyagawa

Takeo Haga

Norimitsu Kito

Yoshitaka Nagao

Ryoichi Urahara

A chip-type semiconductor ceramic electronic component including a ceramic body made of a semiconductor ceramic, first external electrodes formed on opposite end surfaces of the ceramic body, and second external electrodes extending to cover surfaces of the first external electrodes and part of side surfaces of the ceramic body. A curvature radius of a corner portion of the ceramic body is R (&#x3bc;m), a maximum thickness of a layer of the first external electrode layer, which is in contact with the ceramic body, measured from the end surface of the ceramic body is y (&#x3bc;m), and a minimum thickness of a layer of the second external electrode, which is in contact with the side surface of the ceramic body, measured from an apex of the corner portion of the ceramic body is x (&#x3bc;m), and 20&#x2266;R&#x2266;50, &#x2212;0.4 x+0.6&#x2266;y&#x2266;0.4 is satisfied when 0.5&#x2266;x&#x2266;1.1, and &#x2212;0.0076 x+0.16836&#x2266;y&#x2266;0.4 is satisfied when 1.1&#x2266;x&#x2266;9.0.

Chip-type semiconductor ceramic electronic component

In a method for sorting PTC elements having different resistance-temperature characteristics, a predetermined voltage that allows a current to sufficiently decay is applied to each of PTC elements A and B, and the PTC elements are sorted on the basis of the difference between the times required for the currents passing through the PTC elements B to reach a predetermined value (e.g., 52 mA).

Method for sorting positive temperature coefficient (PTC) elements

A chip thermistor includes a layered structure having a thermistor element and a substrate stacked one above the other with an electrically insulating layer in between. The thermistor element has a pair of surface electrodes on surfaces of a planar thermistor body, and a pair of outer electrodes each on a corresponding one of mutually opposite end parts of this layered structure. Each of these outer electrodes is electrically connected to a corresponding one of the surface electrodes. The pair of surface electrodes is preferably each formed so as to cover a major portion of one of the main surfaces of the thermistor body and to reach the opposite main surface through one of its side surfaces, while in a mutually separated and electrically insulated relationship. The substrate may preferably be another thermistor body.

Chip thermistor

Thermistor chips are produced by first obtaining elongated strips made of a sintered ceramic plate having a specified resistance-temperature characteristic and having thereon a plurality of mutually parallel grooves extending perpendicularly to its direction of elongation. On each of these strips, ohmic electrodes are formed, one extending continuously from one of its main surfaces to one of its side surfaces and another extending continuously from the other oppositely facing main surface to the opposite side surface. This may done by covering the strip completely with an electrically conductive film and separating it into two areal parts by forming a longitudinally extending slit on each of the main surfaces. These strips are then stacked one on top of another by aligning the grooves on each of these strips and adhesively attached together with a glass paste in between. The layered structure thus obtained is broken up along the aligned grooves to obtain individual units of which newly exposed surfaces may later be covered by an electrically insulating material.

Method of producing thermistor chips

A chip thermistor is produced by providing a planar rectangular thermistor block with a pair of electrodes formed on its surfaces, each of the electrode being formed so as to be in part on a different one of the main surfaces and extending continuously at least onto one of the side surfaces. The thermistor block thus prepared is cut transversely to obtain a plurality of thermistor elements. A specified number of these thermistor elements are then aligned and stacked one on top of another with their main surfaces facing each other. A layer of an insulating material such as glass with thickness greater than 10 .mu.m is inserted between each mutually adjacently stacked pair of these thermistor elements. Outer electrodes are formed on the outer surfaces of the stacked structure so as to electrically connect to the electrodes on the stacked thermistor elements on their aligned end surfaces.

Chip thermistors and methods of making same

A semiconducting ceramic whose rush breakdown voltage is high and which hardly cracks during lamination is provided. In the semiconducting ceramic having a positive resistance-temperature characteristic, the ratio of intra-granular resistance of the crystal grains and inter-granular resistance between crystal grains which together determine the value of resistance of the semiconducting ceramic is set so that the intra-granular resistance is less than about 20% of the value of resistance of the semiconducting ceramic (not including 0%).

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Higashiomi, Japan

Yoshiaki Abe