In order to validate the applicability of the direct current potential difference method (DC-PDM) to identification of interface cracks, electric field analysis was carried out for a copper plate with a solder ball joined on the surface by the finite element method. The analysis was carried out for different crack depths under the following four conditions; (a) when the shape of interface cracks between solder ball and copper changes, (b) when the radius of solder ball changes, (c) when the distance between the bottom of the copper wire and the interface changes, and (d) when the angle of copper wire changes. It was found from the analysis that the larger crack area ratio gave the larger increase in potential difference and that the effect of the crack shape and the angle of copper wire on the potential difference was small. Finally, the relationship between the crack area ratio and the increase in potential difference was given by a single formulated curve for all the conditions discussed in the present analysis