Measurements of water contact angle on FR4 and polyimide substrates relating electrochemical migration

Contact angle measurements of water droplets were carried out on fiberglass epoxy resin and polyimide substrates related to water condensation effect as an antecedent process of electrochemical migration. It was shown in our previous paper that water condensation intensity depends mainly on the surface roughness (which determines capillary condensation) and on the heat diffusivity of the substrate material as well. However, not only water condensation intensity has a high impact on electrochemical migration but also the water wettability of the surface. The wettability of the different substrates was estimated by the contact angle calculation using the drop shape method. The results correspond to the surface roughness and heat diffusivity differences of the substrates, thus the time to failure values.