Murata Manufacturing Co., Ltd.

Norimitsu Kito

Masahiko Kawase

Hidenobu Kimoto

Ikuya Taniguchi

Yasuhiro Nabika

Yoshiaki Abe

Noboru Furukawa

Ryoichi Urahara

Mitsuaki Fujimoto

Takahiko Kawahara

Thermistor chips are produced by preparing thermistor bodies each having outer electrodes formed on its end parts and dipping them in a solvent so as to melt away exposed surface portions of the thermistor body. In order to efficiently adjust their resistance values so as to produce thermistor chips with resistance values having only small variations from a target value, the resistance value between the outer electrodes are measured for each and they are divided into ranks according to the measured resistance values, and the dipping process is carried out differently for different ranks such that different amounts of the thermistor body material will be melted away.

Method of producing thermistor chips

A thermistor chip is made by first forming first metal layers with a three-layer structure at both end parts of a thermistor block and then forming second metal layers with a three-layer structure on the first metal layers so as to have edge parts that are formed directly in contact with a surface area of the thermistor block and will reduce its normal temperature resistance value. The first and second metal layers are each of a three-layer structure with a lower layer made of a metal with resistance against soldering heat, a middle layer made of a metal with both wettability to solder and resistance against soldering heat, and an upper layer made of a metal having wettability to solder.

Methods of making thermistor chips

Electrodes on both ends of a thermistor chip element each have a first metal layer formed on the thermistor chip element and a second metal layer which has a smaller area than the first metal layer and is formed on the first metal layer such that the mutually opposite edge parts of the first metal layers are exposed. Third metal layers are formed over the second metal layers. A fourth metal layer may be formed between the first and second metal layers.

Thermistor chips and methods of making same

A thermistor chip is made by first forming first metal layers with a three-layer structure at both end parts of a thermistor element and then forming second metal layers with a three-layer structure on the first metal layers so as to have edge parts that are formed directly in contact with a surface area of the thermistor element and will reduce its normal temperature resistance value. The first and second metal layers are each of a three-layer structure with a lower layer made of a metal with resistance against soldering heat, a middle layer made of a metal with both wettability to solder and resistance against soldering heat, and an upper layer made of a metal having wettability to solder.

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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Shiga, Japan

Norimitsu Kito