Socket apparatus for IC packages

A socket for use with a semiconductor device having a plurality of terminals arranged in a pattern comprising a base, an adapter mounted on the base having a semiconductor device mounting seat, a plurality of contact members each having first and second end portions, one end portion of each contact member being fixed to the base in a pattern corresponding to the pattern of the semiconductor device terminals, the other end portion of each contact member having a pair of generally parallel extending arms, each arm having a free distal tip portion, the arms of each pair being movable toward and away from each other to nip and release a respective semiconductor device terminal of a semiconductor device placed on the mounting seat, each arm formed with a butting surface aligned with, extending toward and engageable with the butting surface of the other arm of a respective pair to determine the minimum spacing distance between the tip portions of the arms when the butting surfaces of a pair engage each other, a plurality of contact member opening and closing members, a respective contact opening and closing member disposed between the arms of each contact member and being movable between a first position biasing at least one arm of the respective pair to open the tip portions of the arms and a second position where engagement of the butting surfaces with each other is permitted, and an opening and closing mechanism that moves the contact member opening and closing members between the first and second positions.