R-curve behavior of Cu–Sn3.0Ag0.5Cu solder joints: Effect of mode ratio and microstructure

Double cantilever beam (DCB) specimens were prepared with three different time–temperature profiles to achieve distinct intermetallic microstructures and then tested under mode I and various mixed-mode loading conditions to obtain the R-curves. The time above solder liquidus and the cooling rate were selected to be representative of typical microelectronics production. Both the initiation strain energy release rate and the steady-state values were found to increase with the relative amount of mode II loading and decrease with the thickness of the intermetallic compound layer between the solder and the copper. The effect of the local geometry of the end of the solder layer was found to have only a small effect on the initiation strain energy release rate.