The effect of gelatin on the tin electrodeposition

Tin methyl sulfonate solution has been widely applied in preparing tin films. In this research, semi-bright and bright tin coatings electroplated from the tin methyl sulfonate baths containing and not containing gelatin were observed through scanning electron microscope. The influence of gelatin on the electrodeposition of tin was investigated by X-ray diffraction and polarization analysis. The result shows that gelatin has little influence on the orientation of tin coatings; both the semi-bright and bright tin coatings shows the same preferential growth directions, which are (101) and (112) crystal planes. Without adding gelatin into the methylsulfonic acid tin bath, a lot pores appear on the surface of semi-bright tin coatings, and the void ratio is about 5%. While for the bright tin coatings fabricated from the solution containing gelatin, it has 100% coverage. The cathodic polarization curves prove that gelatin can obviously promote the cathodic polarization, which is in general beneficial for producing uniform, fine and bright tin coatings.