Accurate AOI inspection of resistance in LCD Anisotropic Conductive Film bonding using differential interference contrast

The pressing deformation of conductive microspheres in Anisotropic Conductive Film(ACF) bonding mainly decides the interconnection resistance and bonding quality. Prior works have studied the formation mechanism of microspheres' pressing deformation and bonding resistance, but haven't theorized how to obtain them. This paper has propose to accurately inspect the pressing deformation by differential interference contrast(DIC) imaging and images analyzing. By the deformation inspection, it further proposed to calculate the bonding resistance with the resistance model. Experimental results show it can accurately inspect the conductive microspheres' pressing deformation and interconnection resistance, showing that the unacceptable bumps have a big resistance, over 300 mΩ, while the acceptable bumps have a small resistance, about 126 mΩ. The inspection result is more consistent with the actual resistance than ones from the references for it doesn't have the shortages of parameters acquisition in the references. This paper has theorized how to inspect the ACF bonding resistance which will be useful to electronic packaging, especially in LCD module industry.