Characterisation of lead free solderability of immersion Sn finish on PWBs using wetting balance technique

Abstract

Lead free solderability of pure Sn/Cu finish is investigated in terms of microetch process in printed wiring boards manufacturing. Factors affecting the solderability have been known as whisker, contamination, copper tin intermetallic compound, and the thickness of coating. Lead free solderability, in this paper, is correlated with the surface roughness of Cu film after the microetch process. Solderability is measured by wetting balance technique, and the result shows that the wetting force and the wetting time are negatively correlated with the coefficient of –0˙613. Employing statistical design of experiment, two significant factors, etching time and the mount of Piperidine, affecting the wetting force with respect to the surface roughness of Cu film are successfully identified, and response surface plot for the wetting force is also generated for visual an aid of interaction between the two parameters.

Keywords:

• IMMERSION SN
• WETTING BALANCE
• SOLDERABILITY