Development of Sn-Bi systems lead-free solder paste

The contents of solvent, rosin and activator were adjusted to obtain the most appropriate proportion of the flux for Sn-Bi based lead free solder material by a series of orthogonal experiments. Compared with some commercial Sn-Bi based solder pastes, some tests about the solder paste, such as solder ball test, wettability test and slump test had been carried on. It was found that the self-made Sn-Bi based solder paste had an excellent performance. The welding spots had good appearance; the residues solidified well. The effect of the solder powder ratio on rheological and printing behavior had been studied. When the mass ratio was 12:88 wt%, the best rheological and printing properties of solder paste could be obtained.