Characterization of Wire Bondability on Overhang Structured Chip in Multi Chip Package

Characteristics of wire bonding on the overhang structured chip were investigated in this study. During the wire bonding process, chip crack and bondability were severe factors for thin wafer bonding. Chip crack was investigated by chip strength test and parametric study was performed by changing bonding parameters, constant velocity, force, and power. Bondability was measured for 500, 700, and 1000 mum overhang length. Bonding strength was tested by ball shear test method. 700 mum overhang showed better performance than 500 mum. 1000 mum overhang showed very low bondability. Bonding characteristics were observed by numerical FEM method. Nonlinear dynamic analysis was performed. Unstable contact pressure and shear stress were observed between ball and metal pad. Noise of reaction force was increased with overhang length.