Reliability of lead-free copper columns in comparison with tin-lead solder column interconnects

The thermo mechanical behavior of the ceramic lead-free copper column grid array (CuCGA) package has bee characterized under accelerated thermal cycling using high sensitivity moire interferometry and compared with conventional ceramic tin-lead column grid arrays (CCGA). Unlike tin-lead columns, where the failure occurs at the column near the top of the solder fillet and through the thickness of the column, in the CuCGA, the failure is found to occur first in the solder fillet along the periphery of the copper column that propagates along the boundary of the column and solder fillet. The accumulated plastic deformation per cycle is bigger in tin-lead columns compared to the copper columns. A deformation mechanism is provided to explain the nature of this failure.