| 摘要 |
PURPOSE:To prevent a lead from thinning and a bad influence from dross on the lead, by carrying out etching for a metallic plate and stopping the etching when the dross by laser cutting has been almost entirely peeled away. CONSTITUTION:This invention deals with a lead frame made of metallic plate with a thickness of 0.3mm or below and having a minimum lead pitch not more than twice the plate thickness, while a minimum width of a slit 2 between the leads is not more than the plate thickness. In a first working step, the metallic plate 1 is coated on both sides with an etching-proof resist film 2. In a working second step, a laser beam is cast to the metallic plate 1 coated with the resist film 2 to cut the metallic plate 1 in a desired shape. In a third step, the metallic plate 1 is etched and the etching step is stopped when the dross caused by the laser cutting has been almost entirely peeled away. Then, the thinning of the lead is kept to a minimum without causing a bad effect on these productive steps. |
