Tin Displacement Plating on Copper Using Alginate Gel Particle

Tin displacement plating has been used for improvement of soldering adhesion. Conventional displacement plating methods need a masking process for pattern plating. In the present study, we developed a non masking displacement plating method by using an alginate gel particles. A 10×10−3 cm3 sodium alginate solution was dropped into an aqueous solution containing 5 wt% tin sulfate and 0.83 mol dm−3 thiourea by using a microsyringe. The spherical gel particles were prepared by crosslinking between alginate and Sn2+. The average diameter of the gel particles was about 2 mm. A copper sheet was used as a substrate. An alginate gel particle containing electrolytes was attached to the copper surface and left for 30 min at 25°C. A circular tin film formed on the copper substrate with high uniformity and a sharp edge line. The diameter and thickness of the tin film was about 450 μm and 0.4 μm respectively.