Do I have to choose the SnAgCu alloy as my Pb-free solder?
Not necessarily. There are other alternatives on the market. The primary alternatives tend to include bismuth (Bi), indium (In), or nickel (Ni). Examples include: • SnAgBi • SnAgIn • SnAgBiIn • SnNiCu (SN100) The exact alloy compositions can vary widely, except for SnNiCu. It is dependent upon the desired characteristics, primarily the melt temperature and degree of “shininess.” Companies wanting a “drop-in” replacement have selected SnAg-based alloys with higher concentrations of Bi and In (up to 6 wt%). Lower concentrations result in melt temperatures closer to SnAgCu, but with potentially a better look and feel. SnNiCu has especially shown improved manufacturability and shininess in regards to wave-soldered interconnections (read more here). Except for SnAgCu, however, none of the alloys have the test-to-field correlation necessary to provide some degree of assurance of design life. If solder joint robustness is not a concern for your product, then other alloys can definitely be con
