A new thermal-fatigue life prediction equation for a plastic ball grid array (PBGA) package with 95.5wt%Sn4.0wt%Ag0.5wt%Cu lead-free solder balls is proposed in this investigation. The test vehicle consists of the PBGA package, a lead-free PCB, and a lead-free solder paste (95.5wt%Sn3.9wt%Ag0.6wt%Cu). The coefficients of the fatigue equation presented herein are determined by best fit of the test vehicle's isothermal fatigue data tested at 60degC. Failure modes and locations of the failed samples are discussed