PTC thermistor and method for manufacturing PTC thermistor

Abstract

Provided is a PTC thermistor including a barium titanate-based semiconductor ceramic, which is low in Curie point, capable of being operated at low temperatures around room temperature, and low in room-temperature resistance, with high resistance-temperature characteristics. As the semiconductor ceramic constituting the PTC thermistor, a semiconductor ceramic is used which contains: a perovskite-type compound including Ba, Ti, Sr, and Ca; Mn; and a semiconducting agent, and in which, when the total content of Ba, Sr, Ca, and the semiconducting agent in terms of parts by mole is regarded as 100, the Sr content a in terms of parts by mole and the Ca content b in terms of parts by mole satisfy: 12.5 ‰¤ b ‰¤ 17.5 in the case of 20.0 ‰¤ a ‰¤ 22.5; and 12.5 ‰¤ b ‰¤ 15.0 in the case of 22.5 ‰¤ a ‰¤ 25.0, and when the total content of Ti and Mn in terms of parts by mole is regarded as 100, the Mn content c in terms of parts by mole satisfies: 0.030 ‰¤ c ‰¤ 0.045.

Description

technical field [0001] The present invention relates to a PTC (Positive Temperature Coefficient, positive temperature coefficient) thermistor using a barium titanate-based semiconductor ceramic having positive resistance temperature characteristics. Background technique [0002] As a barium titanate-based semiconductor ceramic composition having a positive resistance-temperature characteristic, for example, a semiconductor ceramic composition disclosed in Patent Document 1 is known. [0003] The semiconductor ceramic composition of this Patent Document 1 is a composition having a positive resistance-temperature characteristic mainly composed of barium titanate, and contains 20 to 30 mol of strontium titanate, 0.05-0.20 mol of calcium titanate, 0.05-0.15 mol of manganese oxide, 2.5-3.5 mol of silicon oxide, and 0.25-0.30 mol of oxides of rare earth elements. [0004] The semiconductor ceramic composition of this patent document 1 can be used suitably for the PTC thermistor o...

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Problems solved by technology

[0005] However, in the semiconductor ceramic composition of Patent Document 1, although the characteristics of low resistance and high withstand voltage can be obtained, in order to realize high-precision temperature detection, the PTC characteristics (relative to the change in resistance vs. The characteristics of the size of the temperature change, and the greater the resistance change relative to the temperature change, the better), there is a problem that it is not necessarily possible to achieve sufficient characteristics

[0006] Therefore, in the case of using the semiconductor ceramic composition of Patent Document 1, it is actually impossible to obtain a PTC thermistor for overheat detection with desired characteristics.

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