Influence of electric field, liquid film thickness, and sodium chloride deposition on atmospheric corrosion of Cu

Abstract

Printed circuit boards (PCBs) are prone to failure due to the influence of environmental factors such as humidity, salt spray, and electric fields during usage. As the lead pitch of PCBs decreases and these environmental factors become challenging to control, corrosion becomes unavoidable. This study used a self-built thin liquid film–electric field coupling environment in an in situ electrochemical testing apparatus. PCB-Cu electrodes were evaluated using open-circuit potential and polarization curve tests on the thin liquid film. This study systematically investigated the effects of external electric field bias, sodium chloride deposition, and liquid film thickness on PCB-Cu corrosion. The results showed that increased bias promoted Cu corrosion in the coupled environment and altered electrode reactions. The cathodic process transitioned from activation control at 0–1 V to hydrogen evolution electrochemical control at 3 V for electrode reactions. Increased sodium chloride deposition enhanced the Cu corrosion rate in the coupled environment primarily due to Cl− damaging the corrosion product film. Under different liquid film thickness conditions, the corrosion rates can be ranked as 200 μm > 300 μm > 100 μm, with 200 μm exhibiting the highest corrosion rate and marking the transition point from the cathodic to anodic control of the corrosion reactions. Orthogonal analysis results indicated that bias was the most influential factor affecting Cu corrosion, followed by liquid film thickness and sodium chloride deposition.