Head on pillow defects in BGAs solder joints

The growing use of lead-free soldering, ultra-fine pitch and area-array devices in electronics manufacturing create new type of defects, such as “head-on-pillow” (HoP). The head-on-pillow soldering defect occurs as a result of the incomplete merging of the BGA/CSP component sphere and the molten solder paste during reflow. This defect was observed during realization of our research, mainly in solder joints of BGA676 components. To prevent and reduce the head-on-pillow defects as well as understand and address this issue a series of experiments were done.