Below are the results of the measurements of UCN voltage of the constant component of signal- response of the test samples of solder joints of chip imitator of integral circuit (IC) and substrate made of polyimide film while applying periodic sequence of square pulse of electric current. The samples with high and abnormally high UCN voltage level were detected with their resistance still within the range of values for the rest of the samples. The test sample with abnormally high UCN voltage level showed noninertial properties and was the carrier of hidden defects in the area of solder joint (inhomogeneities, pores, thin dielectric layers, metal film corrosion). Qualitative samples showed inertial properties and had low UCN voltage levels, proportional to the durability of pulses of electric current. The results of the measurements prove high informativity of the diagnostic method by UCN level while applying pulses of electric current, and the sensitivity to the hidden defects in the area of solder joints ICs. The results of the work can be used while working out automatized means of operational integral electrophysic diagnostics of conducting test IC structures with high requirements to their maintenance reliability.