| 摘要 |
PROBLEM TO BE SOLVED: To enable a current switch device to have a low resistance in its conductive conduction and to have a very high insulation resistance in its non- conductive condition by forming a bismuth metal or a bismuth group alloy film causing volume shrinkage in its melting condition on a substrate and providing a protective layer made from an electrical insulating material thereon. SOLUTION: A bismuth metal or a bismuth group alloy film 3 on a substrate 1 is melted with a volume shrinkage of more than the melting point by heat due to rise kin temperature surrounding a device or current through the device. Electrical conductive condition of the metal film 3 is then destroyed, and the electrical resistance is increased instantaneously so as to become an electrical insulating condition and cut off the current. When device temperature is lowered, the electrical conductive condition is restored, since the volume of the melted metal is increased due to solidification. A linear processing position 4 is provided at one point of the bismuth metal or the bismuth group alloy film 3, and the value of the cut-off current becomes constant in a switching device, while identifying a position for cutting off electrical conducting. The electrical resistance is 1 ohm or less in the conductive condition and a few hundreds ohms or more in the non-conductive condition.
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