Dynamics Features of Cu-Wire Bonding During Overhang Bonding Process

Cu-wire overhang bonding process is investigated first by a high-speed camera system. It was found that the greater impact, rebound, and deflection of overhang die during the Cu-wire bonding process happen since a hard Cu ball hits with the die with a 1.0-μm-thick Al pad, which affects the bonding strength. When the thickness of the Al pad on the die increases to 2.8 μm, its microhardness is three times lower than that of the 1.0-μm Al pad, which will help to improve the dynamics features of hard Cu overhang bonding. Real-time dynamics features prove that the loading process of the 2.8-μm-thick Al pad is much more stable than that of the 1.0-μm-thick Al pad. Furthermore, impact and rebound reduce significantly; thus, the shear strength of Cu-wire overhang bonding increases significantly.