The Influence of the Stamping Parameters on the Warpage of Leadframe

Warpage tends to occur when the stamped leadframe strip is soldered with silicon-dies and baked during the packaging process. This causes offset or fall-off of the silicon-dies near the both ends of the leadframe strip. The length of the strip must be shortened to avoid the excessive warpage, and therefore the production yield is reduced. The situation worsens when the leadframe is not carefully stamped. In this paper, FE analysis was used to simulate the hole punching process as well as the baking process for a simplified leadframe unit attached with a silicon-die. The parameters investigated include the punch/die clearance, the blank-holder force, and the shoulder radii of both the punch and the die. The result shows that the main cause of the excessive warpage in baking is by the worn-off of the punch-shoulder radius.