Effect of anisotropy on springback of integrated circuit leadframes

In order to meet the stringent requirements for high lead count packages, a thorough understanding of springback behavior becomes essential in the forming of integrated circuit leadframes. Plastic anisotropy of leadframe materials is known to be one of the key factors affecting springback. However, insufficient theoretical work has been done in the past to study the effect of plastic anisotropy on springback in integrated circuit leadframe forming. In this paper, a new plane stress bending model, taking account of plastic anisotropy, has been proposed to predict the deformation behavior and springback of narrow strips. Comparisons between theoretical predictions and experimental results have been made. It is shown that the results predicted by the anisotropic model are in better agreement with the experimental observations than those given by the isotropic plane stress model. These findings are significant because they provide useful guidelines for tool designers.