Electrochemical Migration

Failure Mechanism

Water films absorb water-soluble flux residues from preceding soldering operations, creating an electrolyte bridge that dissolves copper from positively biased features. Metal ions reduce at the cathode surface, precipitating microscopic metallic filaments that lengthen toward the anode until current leakage trips protective circuits or fuses the narrowest metal strand. Atmospheric humidity accelerates the transport process, while elevated operating temperatures increase ionic mobility within the thin moisture layer trapped beneath component bodies.

Testing Protocol

Standardized water drop tests and humidity bias chambers evaluate printed circuit board susceptibility by applying direct current voltage across closely spaced comb patterns while recording leakage current spikes. Destructive cross-sectional analysis combined with energy dispersive X-ray spectroscopy confirms the composition of suspected metallic dendrites after environmental stress testing concludes. Passing criteria require leakage current to remain below specified microampere thresholds throughout prolonged exposure to eighty five percent relative humidity at eighty five degrees Celsius.