Electrochemical migration behaviour of surface finishes after vapour phase reflow soldering

This paper presents a comparative study of electrochemical migration behaviour of different surface finishes subjected to vapour phase soldering or infrared reflow process. Three different surface finishes were studied: immersion silver, immersion tin and bare copper on glass fibre epoxy board (FR4) with and without solder mask layer. After the application of the lead-free solder profile on the samples, water drop tests were carried out with distilled water. The developed dendrites were observed by scanning electron microscope in order to study the dendrite morphologies. The electrical characteristics of the short formation on the different samples were also compared. According to the statistical evaluation, it was shown that applied reflow soldering technology could have impact on the electrochemical migration behaviour of the different surface finishes.