Microstructural evolution and atomic transport by thermomigration in eutectic tin-lead flip chip solder joints

Dan Yang*, B. Y. Wu, Y. C. Chan, King-Ning Tu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

The thermomigration behavior of eutectic tin-lead flip chip solder joints at an ambient temperature of 150 °C was investigated in terms of microstructural evolution, atomic transport, and numerical simulation. Pb accumulation and phase separation were observed in solder joints near a melting temperature after 50 h, which was supported by energy dispersive x-ray and element mapping analysis. It is believed that Pb atoms migrated from the chip side (the hot side) to the substrate side (the cold side) under a temperature gradient. Thermal electrical finite element simulation for the real flip chip test structure showed the existence of a temperature difference between the substrate side and the chip side. In addition, a temperature gradient above 1000 °Ccm across the adjacent unpowered solder joints was predicted. This was also verified by temperature measurements with thermocouples. The atomic flux of Pb due to thermomigration was calculated here, which was agreeable with the values originally reported. Also, the driving force of thermomigration was estimated to be 10-17 N, even approaching the same order with that of electromigration under a current density of 104 A cm2.

Original languageEnglish
Article number043502
JournalJournal of Applied Physics
Volume102
Issue number4
DOIs
StatePublished - 7 Sep 2007

Fingerprint Dive into the research topics of 'Microstructural evolution and atomic transport by thermomigration in eutectic tin-lead flip chip solder joints'. Together they form a unique fingerprint.

Cite this