Head-in-Pillow BGA Defects

Head-in-Pillow (HiP) solder joints have become a more prevalent defect as the industry continues to migrate to more lead-free assemblies. This defect occurs when an electronic and mechanical bond is not made between BGA solder spheres and the solder paste during reflow. Perhaps a larger problem may be that this defect can make it through both x-ray inspection and in-circuit testing undetected, only to surface in the field as the result of thermal and mechanical stress. Also complicating the situation are changes in solder sphere to low silver alloys with or without dopants for improved shock resistance. New surface oxides may be more difficult for current solder paste technologies to overcome and facilitate reliable solder joint formation.