POSITIVE CHARACTERISTIC THERMISTOR AND METHOD FOR MANUFACTURING POSITIVE CHARACTERISTIC THERMISTOR

摘要

A component element (1) is formed from a semiconductor ceramic in which the chief constituent is a BaTiO₃-based composition and some of the Ba is substituted with alkali metal and Bi, and the component element (1) is provided with: a high-resistance layer (4) having high room-temperature resistance and a high resistance/temperature coefficient; and low-resistance layers (3a, 3b) having low room-temperature resistance and a low resistance/temperature coefficient. The high-resistance layer (4) is formed on an outside surface section contacting external electrodes (2a, 2b), and also the low-resistance layers (3a, 3b) are formed in a middle section separated from the external electrodes (2a, 2b). The thickness (y) (μm) of the high-resistance layer (4) and the mol ratio (x) of the alkali metal in the chief constituent satisfy the relationship of 10≤y≤-3500x+525(0.010≤x≤0.147). Also, the component element (1) can be manufactured by a sheet processing method. In this way, a non-lead-based PTC thermistor can be implemented having good reliability in which deterioration over time of resistance can be suppressed without impairing PTC characteristics even when current is passed for a long period of time, and a method for manufacturing this PTC thermistor can also be implemented.