Solder Surface Deformation

摘要

THIS MONTH WE show the ball surface on area array packages where no solder joint was formed. The joints were intermittent, but one of the surfaces - either the ball or the surface of the solder on the pad - was deformed. This is better known as head-in-pillow (HiP) or head-on-pillow (HoP), depending on the shape formed on the solder adjacent surface. FIGURES 1 and 2 show examples of HiP/HoP. In Figure 1, the surface of the ball is shown after mechanically separating the device from the board. The indent of the solder from the pad on the board is visible.