Lead-free solder alloy
A lead-free solder alloy suitable for use in flow soldering of electronic components to printed wiring boards comprises 0.1-3 wt % of Cu, 0.001-0.1 wt % of P, optionally 0.001-0.1 wt % of Ge, and a balance of Sn. The solder alloy may further contain at least one of Ag and Sb in a total amount of at most 4 wt %, and/or at least one of Ni, Co, Fe, Mn, Cr, and Mo in a total amount of at most 0.5 wt % in order to strengthen the alloy, and/or at least one of Bi, In, and Zn in a total amount of at most 5 wt % in order to lower the melting point of the alloy.
1. A lead-free solder alloy consisting of 0.1-1.5 wt % of Cu, 0.001-0.1 wt % of P, 0.001-0.1 wt % of Ge, 0.03-0.3 wt % of Ni, and a balance of Sn.
2. A soldered joint formed from a lead-free solder alloy as claimed in claim 1 .
3. A soldered joint as claimed in claim 2 wherein the soldered joint is formed by flow soldering.
4. A lead-free solder alloy as claimed in claim 1 containing 0.4-1.0 wt % of Cu.
5. A lead-free solder alloy as claimed in claim 1 containing 0.001-0.05 wt % of Ge.
6. A lead-free solder alloy as claimed in claim 1 containing 0.001-0.05 wt % of P.
7. A lead-free solder alloy as claimed in claim 1 containing 0.001-0.01 wt % of P.
8. A method of performing flow soldering comprising using a lead-free solder alloy as claimed in claim 1 .
9. A method as claimed in claim 8 wherein the flow soldering is wave soldering.