Some lead-free compositions and their melting ranges |
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|---|---|---|
| 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 |
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|---|---|---|
| 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. |
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