Effects of the surface hardness of MIS leadframe on the bonding strength

Molded interconnect system (MIS) is a new generation of substrate technology for traditional QFN, and fine gold wire bonding should be used. While lots of studies focused on the wedge bonding process, the effect of Ni/Pd/Au finish on the bonding force was never verified before. This paper will present a detailed investigation on the wedge bonding on MIS leadframe, and many aspects which affect the gold wire wedge bonding including components, morphology, and hardness were studied. The results show that the hardness of the Ni layer is found directly decides the wedge bonding force with the Ni layer increasing. It is possible to optimize the thickness of Ni/Pd/Au finish material to control the wedge bonding strength.