Estimation of degradation of printed circuit board by growth of ionic migration

To investigate the development and growth process of ionic migration of metals used for wiring, lone term tests on typical printed circuit boards (PCB) have been performed under high humidity and high temperature conditions. A relationship between the electric field (E), the time (t) after which the migration starts to develop and its subsequent rate of growth (ψ) is proposed which can be expressed as ψ=4(Er)^α where values of both A and α depend on the PCB material. Values for A and α have been calculated for three PCBs made of different materials