Design for Relability of Stacked Die CSPs

摘要

Detailed solder joint fatigue models with life prediction capability were established for two types of stacked die CSPs. For enhanced solder joint reliability of stacked die CSPs, it is generally recommended to choose thicker die, a thinner package, a thicker substrate/lead frame, a thinner board, higher solder joint standoff arid a bigger solder pad opening size. Certain design rules learned from single die CSPs are not applicable to stacked die CSPs. The position of the critical solder ball is a variable for SDBGA, so the common practice of using dummy balls for the outermost corner position may not improve the fatigue life. Effects of design variables may be case dependent, so fatigue modeling is efficient to assess solder joint reliability of new package designs — providing cost, time and manpower savings to perform the actual thermal cycling tests.