Surface roughness influence on solderability

The article deals with results of solderability testing of printed circuit boards. The wetting balance test was used for solderability testing. This test makes wetting force measurement possible as a function of time. Measured values are recorded automatically. Surface roughness is one of parameters, which influence surface wetting. The article will present the results and comparison of tested printed circuit boards with different surface roughness. This comparison will be made for several surface finish types. Test specimens of printed circuit boards with surface finishes SnG (galvanic tin), SnC (immersion tin), Cu (pure copper), OSP (organic solderability preservative) and ENIG (electroless nickel immersion gold) were tested. The test specimens were purposely roughened by different abrasive paper before solderability testing. Roughness created on surface finishes were oriented vertically and horizontally.