Application of failure analysis process flow in multifunctional SiP

SiP is becoming a popular technology as it can provide an effective method for system integration and miniaturization. The complex structure and diversity of technologies applied in SiP may cause unexpected failure. Failure analysis of SiP is getting more difficult than that of single die packaging. In this paper, failure analysis of a SiP which integrated four functional dies and one silicon interposer with die-stack structure was studied. Part of SiP samples did not passed function test and different yield of packaging turned out between two batches. Following the failure analysis process flow for pilot run of SiP, nondestructive inspection (X-ray/C-SAM/Probe Test) and destructive inspection (Acid De-cap/Laser De-cap/FIB) were applied to locate the precise failure site and dig out the root cause. The electrical short between bonding wire and exposed trace nearby was affirmed at last. Design optimization was carried out. Meanwhile, in order to improve processing compatibility and yield of packaging, stringent design rule and process specification for SiP, especially for those with long loop, multi-tier bonding wires and fine pitch bonding fingers, were summarized.