Leaching of heavy metal elements in solder alloys

Leaching behavior of heavy metal elements from Sn–3.5Ag–0.5Cu, Sn–9Zn, and Sn–37Pb solder alloys and their joints was investigated in typical H2SO4, NaCl and NaOH solutions. The leaching amount of Sn from solder joints was more than that from solder alloys and the leaching amount of Sn from Sn–3.5Ag–0.5Cu solder joint in the NaCl solution was the most. The surface corrosion products on the solder and their joints were composed of oxide, oxide hydroxide or oxychloride of the component element. Much more surface oxides for the samples treated in the NaCl solution produced than that in the NaOH and H2SO4 solutions.

Research highlights
► Metal leaching from Sn–3.5Ag–0.5Cu, Sn–9Zn, and Sn–37Pb solder joints was studied.
► The employed solution were 0.10 mM H2SO4, 0.20 mM NaOH, and 3.5 wt.% NaCl solution.
► The leaching amount of Sn from solder joints was more than that from solder alloys.
► Leaching of Sn from Sn–3.5Ag–0.5Cu solder joint in the NaCl solution was the most.
► Surface oxides in the NaCl solution were more than that in the other solutions.