IEC 60321: PCB Cleaning — Flux Residue and Ionic Contamination Reliability Risks

The “White Residue” After Soldering Is Not Just Cosmetic — It Is an Electrochemical Migration Risk

IEC 60321 specifies PCB cleaning quality and testing. Post-soldering flux residue absorbs moisture in humid environments, forming ionic conductive bridges between adjacent pads — leading to electrochemical migration (ECM) and short-circuits. NaCl equivalent ≥1.56 μg/cm² indicates ionic contamination exceeding limits.

TNLab — PCB cleanliness is not about “looking clean” — ionic contamination is invisible under a microscope but can destroy a board within months.