| 摘要 |
PURPOSE:To reduce a change rate of a resistance value with the passage of time by a method wherein a borosilicate bismuth glass powder is coated on the whole surface of a thermistor device so that the glass can be diffused into the device. CONSTITUTION:When a thermistor to be used for a level gauge sensor is manufactured, a borosilicate bismuth glass powder is coated on the whole surface of the thermistor device and the glass is diffused into the thermistor device at a heat treatment temperature of 800-900 deg.C. For example, the external circumference of a sintered substance for the thermistor device 3 is ground and is finished to be a size of 1.45mm in diameter. After that, the borosilicate bismuth glass powder which is composed of 6.5% B2O3, 60.5% BiO3 and a remaining part of SiO2, Co2O5 and Li2O is coated on the whole surface of the device 3. After that, the glass is diffused into the device 3 at a heat treatment temperature of 800-900 deg.C. By this setup, a change rate of a resistance value with the passage of time as the level gauge sensor can be reduced and the reliability can be enhanced.
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