PURPOSE: To reduce the generation of a material transfer phenomenon between contacts by making the ratio of the major axis to the minor axis of the formation of Cu crystalline particles of a Cu-Bi alloy 3.0 or larger.
CONSTITUTION: An isolation chamber 1 is partitioned airtight by an insulating container 2 formed cylindrical and metallic lids 4 and 5 provided through connections 3 and 3a at both ends of the container 2. In the isolation chamber 1, a fixed electrode 8 and a movable electrode 9 are arranged at the opposing ends of a pair of electrode rods 6 and 7, and the tips of the electrode 8 and 9 form contacts 14 and 14a. The contacts 14 and 14a are composed of a Cu-Bi alloy, and the whole area of the parts where the ratio of the major axis to the minor axis of the Cu crystalline particles is 3.0 or larger occupies 90% or more. To such an alloy, 0.0001-0.1% of boron is added, and the longitudinal direction of the Cu crystalline particles is arranged parallel to the contact surface. By such a constitution, the material transfer amount can be reduced, the contact resistance property can be improved, and the width of unevenness can be reduced.
SEKI KEISEI
HONMA MITSUTAKA
