| abstract |
Electromigration in microbump connections causes voids in the microbumps, which reduces the lifetime of an integrated circuit containing the microbump. Electromigration lifetime may be increased in microbumps by forming a copper or nickel shell around the solder. The copper shell (220, 408) of one microbump contacts the copper shell (234) of a second microbump to enclose the solder (222) of the microbump connection. The copper shell (220 & 234) allows higher current densities through the microbump. Thus, smaller microbumps may be manufactured on a smaller pitch without suffering failure from electromigration. Additionally, the copper shell reduces shorting or bridging between microbump connections on a substrate (202, 230). Increased connection densities between two dies (202,230)or between a die and a packaging substrate are therefore possible. |