Electrochemical migration behavior of a fine-pitch IC substrate by alternating current

Electrochemical migration properties of fine pitch chip-on-flex (COF) for displays were investigated by a water drop test and scanning electron microscope with energy dispersive spectroscopy. While the time to failure due to ECM is less than 1 s at a direct current (DC) bias of 10 V, it is approximately 330 s at an alternating current (AC) bias of 10 V 10 Hz and approximately 3,940 s at 240 Hz. The ECM failure mode due to AC bias appears to be caused by limitations on the degree of ion diffusion and relatively small changes of the pH, unlike the DC bias case.