Lead Free Solder Information

Some lead-free compositions and their melting ranges

Alloy Composition (wt%) Melting range (°C)
Bi-In 33 In 109(e)
Sn-In 50 In 118(e)
Sn-Bi 58 Bi 138(e)
Sn-Bi-In 20 Bi 10 In 143-193
Sn-Pb 37 Pb 183(e)
Sn-Bi-Zn 8 Zn 3 Bi 189-199
Sn-Zn 9 Zn 199(e)
Sn-Ag-Bi 7.5 Bi 2 Ag 207-212
Sn-Ag-Cu-Sb 2 Ag 0.8 Cu 0.5 Sb 216-222
Sn-Ag-Cu 3.8 Ag 0.7 Cu 217(e)
Sn-Ag 3.5 Ag 221(e)
Sn-Cu 0.7 Cu 227(e)
Sn-Sb 5 Sb 232-240
Sn-Au 80 Au 280(e)

(e) - eutectic

Alloy selection

Family Pluses Minuses
Sn-Cu Cost Melting temperature 227°C,
mechanical properties
Sn-Ag Reliability,
solderability
Cost,
melting temperature 221°C
Sn-Ag-Cu (Sb) Reliability,
solderability,
mechanical properties
Melting temperature 216°C
Sn-Ag-Bi (Cu) (Ge) Melting temperature 206°C,
close to tin-lead eutectic
Paste shelf life,
needs aggressive fluxes,
excessive oxidation,
corrosion.