The application of plastic core solder balls (PCSB) for the assembly of a silicon (Si) interposer die inside a ceramic package has been evaluated for a harsh application. Three different variants of assembly were compared. All variants survived the performed thermal shock cycling and centrifugation. Failures observed after thermal shock cycling indicated a reduced risk of crack formation for Ag-rich solder systems. Roughly 50% of each variant survived a performed application test. Significantly different failure modes were observed after thermal shock cycling compared to after the application test. Individual qualification tests are therefore recommended to evaluate reliability with respect to storage and application.