H. W. Tseng

Electromigration-induced failures at Cu/Sn/Cu flip-chip joint interfaces

We observed various EM-induced failures in current-stressed Cu/Sn/Cu flip-chip solder joints. EM-induced Cu-pad consumption occurred at the current-entry point (maximum current-density) on the cathode interface, and voiding occurred at the other joint corner away from the current-entry point (minimum current-density). We believe that the above various EM-induced failure modes were the result of different current-stressing densities and joule heating at the cathode joint interfaces.

Retardation of electromigration-induced Ni(P) consumption by an electroless Pd insertion layer

In this study, Ni(P) bond pads joined with Sn solder bumps were stressed with a high current density of 104 A/cm2. Serious electromigration-induced Ni(P) consumption and unusual EM-enhanced diffusion of the interfacial Ni3Sn4 compound layer are observed. However the observed EM-induced Ni(P) consumption and EM-enhanced diffusion of the interfacial Ni3Sn4 compound layer can be effectively retarded by introducing an additional electroless Pd layer on the Ni(P) layer. The improvement in EM resistance due to the Pd layer can be attributed to PdSn4 formation and Pd solutes in the interfacial Ni3Sn4 layer.

Abnormal Cu3Sn Growth and Kirkendall Formation Between Sn and (111) and (220) Preferred-Orientation Cu Substrates

(111) and (220) preferred-orientation Cu substrates were successfully produced by varying electroplating current-density. While these preferred-orientation Cu substrates reacted with Sn, serious Kirkendall voids formed at the interfaces between Sn and (111) and (220) preferred-orientation Cu substrates. Also, abnormal Cu3Sn growth occurs; the Cu3Sn layer decreased upon aging and vanished after 1000-h aging. With a prolonged 2000-h aging, a Cu3Sn layer re-grew at the Cu6Sn5=Cu interface. The abnormal Cu3Sn growth was found to highly associate with serious Kirkendall formation VC 2011 The Electrochemical Society. [DOI: 10.1149/1.3608248] All rights reserved.