PURPOSE: To improve dimensional accuracy by forming an opening at the end of a part of inner lead, performing profile machining so that a coupling part is provided between the side face at the end of the inner lead and an island part, and then removing the coupling part after eliminating residual distortion from the material.
CONSTITUTION: Openings 20 for forming the end part 14 of an inner lead 12 are punched through a thin conductor board, followed by profile punching 22. Under a state where a coupling part 18 is left between the side face at the end part 14 and an island part 16, heat treatment or flattening is carried out in order to remove inner residual distortion. Upon removal of inner residual distortion, the coupling part 18 is punched to complete a lead frame. According to the method, residual distortion to be produced at the time of manufacture of the thin conductor board or distortion of material, e.g. machining distortion, to be produced at the time of punching of lead frame can be eliminated.
TAKAYAMA SHOZO
KODAMA HIROFUMI
NAKAGAWA KUNIO
NAGAYAMA SADAO
