Failure induced by thermomigration of interstitial Cu in Pb-free flip chip solder joints

Hsiao Yun Chen, Chih Chen*, King-Ning Tu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

Failure induced by thermomigration in Pb-free SnAg flip chip solder joints has been investigated by electromigration tests under 9.7× 103 A/ cm2 at 150 °C. The fast interstitial diffusion of Cu atoms from underbump metallization into Sn matrix caused void formation at the passivation opening on the chip side. The Cu diffusion was driven by a large thermal gradient and led to void formation even in the neighboring unpowered bumps. When the thermal gradient is above 400 °C/cm, theoretical calculation indicates that the thermomigration force is greater than the electromigration force at 9.7× 103 A/ cm2 stressing.

Original languageEnglish
Article number122103
JournalApplied Physics Letters
Volume93
Issue number12
DOIs
StatePublished - 6 Oct 2008

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