Leadframe having a particular dam bar

摘要

A leadframe comprising a thin-walled portion that is formed in a dam bar portion or a portion that extends from the dam bar portion to a pair of inner leads which are adjacent thereto. By cutting the dam bar portion along the thin-walled portion, the stress that is imposed on a cutting punch is reduced. Thus, it is possible to extend the lifetime of the cutting punch and also to minimize the shear droop formed on the cut surface. The leadframe further has a thick-walled portion formed at the position where the thin-wall portion is formed. The thick-walled portion serves to support the thin-walled portion when the dam bar portion is cut off, thus preventing the dam bar portion from tilting. Accordingly, the dam bar cutting operation can be conducted stably without undesired movement of the dam bar portion, and the stress that is imposed on the leadframe can be controlled so as to be well balanced.