Electrochemical Migration (ECM) Testing

National Technical Systems (NTS)

Testing for electrochemical migration (ECM) would occur in the case of a field failure return. Metal migration between isolated conductors on a completed printed circuit assembly may produce electrical shorts.
Why does this growth occur and what do you need to look for? Basically, we need to know if our assemblies are “dirty.” By dirty, we mean littered with ions. Ions on printed circuit assembly surfaces can cause short circuits. In simple terms, shorts occur when the space between the conductors is bridged by dendrites formed by re-deposited metal ions. This metal migration is best described by IPC as a reverse plating of the conductors in the presence of ions, water and an electrical potential.