Effects of Glue on the Bend Performance of Flip Chip Packages

To combat reliability margin loss in ball grid array (BGA) packages specifically in mechanical shock and vibration testing, companies are exploring the possibility of using glue and complete underfill to mitigate risk to second-level interconnects (SLI). Though glue has been demonstrated to have a positive influence on SLI reliability margin, it can have adverse affects on the rest of the package such as substrate or first-level interconnects (FLI). This paper explains details on how glue modulates the overall reliability of the package. Finite-element modeling (FEM) along with low strain rate bend tests was done to prove the effect of glue on solder joint reliability. Further, shock testing was done to demonstrate how the glue modulates the shock performance. The improvement in SLI reliability was highly dependent on the choice of glue.