Lead frame manufacturing method

A lead frame manufacturing method of manufacturing a lead frame having lead portions, which extend inward from a frame portion like teeth of a comb and each of which has a base portion connected to the frame portion, a center portion connected to the base portion, and side surface portions connected to both side surfaces of the center portion to have a thickness that is smaller than other portions, by a stamping, comprising the steps of:

• forming a plurality of opening portions, which extend in an extending direction of the lead portions, by punching predetermined portions of a metal plate by virtue of the stamping;
• forming crushed portions, which extend from crushed margin portions to insides of the opening portions, by pushing the crushed margin portions, which are defined in predetermined portions of the metal plate in vicinity of the opening portions, by virtue of the stamping to reduce a thickness;
• defining a width of the side surface portion and the center portion to assure an interval between the lead portions and also defining a width of a top end portion and a width of the base portion connected to the center portion, by punching center portions of the crushed portions except predetermined both-side portions and predetermined portions of the metal plate in vicinity of peripheral portions, in which the crushed portions of the opening portions are not present, by virtue of the stamping;
• and
• defining the top end portions by punching a predetermined portion of the top end portion by virtue of the stamping.