Effect of PCB orientation on condensation-related dendritic failure due to electrochemical migration

High-voltage electronic systems face increasing reliability challenges due to corrosion and Electrochemical Migration (ECM) in harsh environmental conditions. Printed circuit boards (PCBs) are particularly vulnerable as water film forms under humid conditions. This creates conductive paths between metallic components, leading to reduced surface insulation resistance and leakage currents, ultimately leading to ECM. Operational PCBs are frequently installed vertically or at angles depending on device specifications, potentially altering condensed droplet behavior due to gravitational effects. This study investigates how PCB orientation influences condensed droplet development and coalescence into a continuous water film between biased points and subsequent failures. A 16-pad test PCB featuring equidistant square copper pads was subjected to high humidity condensation conditions in three distinct orientations: horizontal, vertical, and angled. The experimental setup allowed for water droplet formation, coalescence and dendritic growth progression under controlled environmental conditions. Findings revealed significant orientation-dependent differences in water droplet coalescence behavior and subsequent failure rates. Horizontal PCB demonstrated the most severe coalescence effects, resulting in accelerated dendritic formation and highest propensity for electrochemical failures. Conversely, vertical orientation exhibited the lowest failure rates, with reduced droplet coalescence due to gravitational drainage effects that minimized sustained conductive path formation between biased components. Critical mass of droplets calculated revealed that lesser number of droplets can remain on the surface without sliding off, with increasing inclination angle of the surface (tending towards hydrophobic). Furthermore, X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS) were used to characterize the corrosion products formed with varying orientations.