Theoretical analysis of springback in bending of integrated circuit leadframes

The development of high lead-count integrated circuit (IC) packages imposes more stringent demands on the forming quality of IC leadframes. A thorough study on the springback of narrow strips becomes highly essential. However, most of the published works on the springback problem still only consider wide strips and are based on the plane-strain assumption, which are inappropriate for leadframe geometry. In this paper, a strain-hardening plane-stress bending model has been proposed to predict the deformation behavior and springback of narrow strips. Springback prediction for a typical leadframe material has been illustrated. Comparisons between the theoretical predictions and the experimental results and those obtained by two theoretical models reported in the literature have been made. Much improvement has been observed in using the present model. The results of the analysis are of high significance and can provide useful guidelines for tool-designers.