US Patent 7250135 Pb-free solder alloy

Provided is a Pb-free solder alloy used for mounting electronic parts on a printed circuit board. The Pb-free solder alloy is highly resistant to oxidation and impact. The Pb-free solder alloy includes Ag of 2.8 wt % to 4.2 wt %, Cu of 0.3 wt % to 0.8 wt %, Ge of 0.0001 wt % to 0.01 wt %, In of 0.001 wt % to 0.2 wt %, and the balance of Sn. The Pb-free solder alloy having this composition also has a high shear strength and low brittleness factor after bonding. Thus, the Pb-free solder alloy has high quality mechanical properties, to form a high quality joint.