PURPOSE: To prevent the generation of inferior goods due to one-sided extension or warpage by stamping a shape such as a character or figure to be expressed by a continuous line in press stamping.

CONSTITUTION: Characters with a length of 1.0mm and a width of 0.8mm are applied to the single surface of the side rail of a lead frame with a width of 53mm made of a 42 alloyed copper material with a plate thickness of 0.15mm over a width of 3.0mm by press stamping. As a result, the percent defective due to lateral warpage is 1% in conventional stamping forming a shape such as a character by a line whereas lateral warpage is 0.1mm or less and percent defective becomes 0.5% or less. Extension is 0.12mm per a length of 150mm in a conventional method but 0.08mm in this method.