Chemical synthesis of Cu-Sn powder by tin(II) cementation with copper in aqueous solution

The method of Cu−Sn alloy powder chemical synthesis based on tin(II) cementation with copper powder in aqueous solution has been devised. Tin content was controlled up to 95 at.% by the duration of cementation and Sn(II) : Cu molar ratio in the solution. Mechanism and kinetics of complicated reduction-oxidation reactions proceeding during Sn(II) cementation were revealed. The occurrence of overstoichiometric copper corrosion in the presence of thiourea and chloride ions was found. Partial dissolution of the reduced tin and the reduction of the dissolved Cu(I) were disclosed. Bronze powder obtained by cementation in aqueous solution contained crystalline phases of tin, copper and η-Cu6Sn5, δ-Cu41Sn11 and ξ-Cu10Sn3 phases. It was found that intermetallic compounds were formed in the result of copper and tin atoms low temperature diffusion and simultaneous reduction of Sn(II) and Cu(I). The grains in the powder were about 3 µm in average size with numerous nanoparticles 40-200 nm in diameter on their surface. The powder can be applied for soldering, sintering, it can be pressed in tablets and mixed with liquid fluxes for soldering.