Package-On-Package Mechanical Reliability Characterization

POP (package-on-package) integration is achieved by stacking laminate substrate packages in vertical direction and interconnecting them with solder balls. Some mechanical reliability issues were addressed through POP development. In particular, package warpage and Si delamination were dominate issue. Package warpage was characterized with FEM-modeling, Shadow Moire and viscoelastic property measurement. Substrate and mold compound optimization techniques are explained in this paper. Also, Si delamination was characterized with FEM-modeling, OMI strain tool (digital image analysis), scratch tester and stress senor TEG. Si surface strength was measured with scratch tester. Si stress and displacement in the package were measured with OMI strain and stress senor TEG. Design optimization for Si delamination is also explained in this paper. Board level drop test performance is also critical issue for POP. So, nano particles of a solder effects on drop test performance is described. Co, Ni, Pt , Al, P, Cu, Zn, Ge, Ag, In, Sb or Au inclusions in Sn-Ag based lead free solders were evaluated to study if these nano particles can improve drop test performance. It was found that some nano particles could improve the performance. This papers describes POP mechanical reliability characterization with some tools.