전력 반도체 리드 프레임용 구리 박판의 피어싱 공정에서 펀치 선단의 기하학적 형상이 전단면에 미치는 영향 연구

초록

As the demand for power semiconductors in the electric vehicle (EV) and AI data center industries surges, the demand for lead frames is also expanding. High-quality sheared surfaces of lead frames play a critical role in ensuring electrical connectivity and reliability between chips and PCBs. Therefore, it is essential to secure an effective sheared area by minimizing product defects such as excessive rollover and burrs, which can cause short circuits and contact failures. In this study, the characteristics of the sheared surface were evaluated by applying punches with different profiles and edge radii in the piercing process. A parametric study on the punch tip geometry was conducted for C10100 copper (0.6 mm thickness) with a clearance of 3.3% as the primary process variable. Measurement results showed that the rollover decreased as the profile and edge radius increased. Measurement results indicated that the rollover depth decreased from approximately 26% to 14% as the punch profile angle increased from 60° to 150°. Additionally, under the 90° profile condition, the rollover depth reduced from 122μm to 73μm as the edge radius increased from R0.15 to R0.6mm. This appears to result from the transition of the deformation mode from bending-dominant to pure shearing as the profile angle and edge radius increase, which suppresses material inflow at the punch entry and alleviates local stress concentration. The shear surface characteristics of the C10100 copper thin sheet obtained in this study align with the typical ductile fracture mechanisms and sheared edge morphology observed in sheet metal blanking. However, the highly ductile nature of oxygen-free copper necessitates tighter control of punch geometry to secure a sufficient burnished zone compared to conventional steel or aluminum alloys.

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