Effects of Square Wave Frequency on the Current Steps Caused by Copper Dendrite Formation on a Printed Circuit Board

Electrochemical migration (ECM) is a major concern in modern electronics because miniaturization has reduced insulation distances and electronics are now operated in harsher environments than before. Previous studies on ECM have predominantly used direct current (DC), even though many electronic devices are driven by square wave signals, e.g., in data communication and other digital applications. Square wave signals also constitute the basis of switching power electronics devices, such as frequency converters. In this study, the ECM of copper was investigated using unipolar 12 V square wave signals from 5 Hz to 100 kHz with a 50% duty cycle. The focus was on the current increase that occurs when the first dendrite bridges from the cathode to the anode. The current steps at each frequency were measured and the least squares method was used to evaluate the possible correlation between frequency and current step size. The results of this study showed that the current steps were greater at higher frequencies, indicating a smaller impedance of the dendrites at higher frequencies. The smaller impedance could be caused by, e.g., a smaller resistance or a higher capacitance or a combination of these two.