HSOP package mold process development

SOP (Small Out-line Package) has a very broad application in semiconductor for a long time. HSOP is the SOP package with heat sink on lead frame. This paper is focusing on HSOP package assembly development. This paper described the main structure of HSOP package, especially for the lead frame (LF) with riveting heat sink to LF. In terms of assembly process flow, solder wire die attach process, wire bond process and mold process are main challenges for HSOP assembly development. This paper is focusing on HSOP mold process development. Incomplete fill for the area around the rivet and heat sink backside delamination were the main two issues in the mold process study. Through transfer pressure optimization, incomplete fill issue cannot be much improved even using different compound with good mold flow ability. Through mold process study using LF with different riveting area design, the LF with narrower riveting area design can improve the incomplete fill. As for the heat sink backside delamination, the DoEs were performed to improve the heat sink backside delamination including mold flow evaluation and mold parameter optimization. Finally, the heatsink backside delamination was largely improved. In addition, one HSOP package had been performed preliminary reliability evaluation and achieved no electrical fails up to TCI000 (-50C~150C) and 1008hrs HTSL at 150C. Decapped units after Temperature cycle (TC) and high temperature storage life (HTSL) can achieve to have no issue in terms of wire pull strength measurement and ball shear strength measurement. All of the current evaluation experiences will be helpful for further HSOP assembly development.