Effect of electromigration in the anodic Al interconnect on melting of flip chip solder joints

摘要

Melting of eutectic SnPb flip chip solder joints has been observed to occur frequently in dc electromigration tested with current density above 1.5 X 10~4 A/cm~2 at an ambient temperature of 100℃. It has been found that it is not due to the Joule heating of the solder bump itself, but rather due to the Joule heating of the on-chip Al interconnects. The current density in the Al approaches 2 X 10~6 A/cm~2 and electromigration has especially generated voids at the anode of the Al. The damage has greatly increased the resistance of the Al, which produces the heat needed to melt the solder joint. The results of electrothermal coupling analysis show that when the resistance of the Al line changed threefold, the solder bump melted.