Reliability improvements in solder bump processing for flip chips

A plated solder-bump process used for the manufacture of high-reliability flip chips is described. Characterization work done to improve the process manufacturability and the resulting product reliability gains are reviewed. Two detailed studies of the thin-film deposition conditions and the Cu pedestal plating parameters are described. Recommendations implemented as a result of these studies have reduced the bump-interconnect-failure level from a defect rate of ~500 p.p.m. to <10 p.p.m. Excellent temperature cycling performance of assembled hybrids was obtained. The process has been used in high-volume production to manufacture ICs used in automobiles (under-hood application). In process capability has improved from a C_p<1 to C_p>1.5. This work highlights the need and the benefits of detailed characterization, which results in more robust manufacturing processes and eventually in more reliable product performance