Microstructural study of the initiation and formation of immersion tin coating on copper

The initiation and growth of immersion tin coating from hydrochloric acid based and methanesulphonic acid based baths on the inner surface of copper tube was studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The formation of immersion tin coating crystallites from hydrochloric acid based bath occurs semi-coherently with copper substrate. Tin crystallites grow actively both in vertical and horizontal directions yielding an equiaxial grain structure. The immersion tin deposition from methanesulphonic acid based bath proceeds by the formation of tin nanocrystals. These nanocrystals transform into columnar grains during the grain growth process. Differences in the coating formation characteristics between studied baths are reflected to the microstructural details and properties of coatings, such as surface morphology, porosity and adhesion.