Investigation of kinetics of ECM dendrite growth during corrosion in electronics

Corrosion-related failures are critical for electronics reliability in various technological sectors, with a wide range of systems shifting towards the use of high voltage and power. Miniaturization and high voltage between closely spaced connectors induce a higher risk of dendrite formation due to electrochemical migration (ECM) when connected by a condensed water film. Shorting caused by ECM dendrites is a prominent failure mechanism in electronics, which at higher voltage could even lead to incidents of fire. Dendrite growth occurs by metal dissolution and electric field assisted deposition, while dendrite composition and shorting characteristics are determined by the kinetics of growth, controlled by the current. To study the kinetic factors related to dendrite growth, a galvanostatic approach with applied current in the range of 0.5 µA to 5 mA was employed on a simple test PCB consisting of two copper pads. Electrochemical testing was supplemented by chemical analysis of dissolved species in a micro-volume of solution using ICP-OES, while characteristics of dendrite as a function of current levels were analyzed using XPS, SEM-EDS and TEM. Dendrite growth and pH gradient increased with current levels. Dendrite composition varied depending on the current levels, while it was suggested that hydrolysis reactions rate determined local pH and dendrite morphology rather than the level of copper dissolution (Total charge QT/Charge consumed by Cu dissolution QCu>1 for low and high current levels with shorting). A complementary potentiostatic test verified this understanding of charge consumed (QT/ QCu>1 at 2 V and 48 V applied voltage, without dendritic shorting).