An investigation was made of the polarity effect of electromigration upon the kinetics of intermetallic compound formation at the anode and cathode of solder V-groove samples. V-groove solder line samples, with a width of 100µm and a length of 500 to 700µm, were used to study interfacial intermetallic compound growth between Cu electrodes and Sn-3.8Ag-0.7wt%Cu solder under various current density and temperature conditions. The current densities were in the range of 103 to 104A/cm2 at 120, 150 or 180C. The same types of intermetallic compounds, Cu6Sn5 and Cu3Sn, formed at the solder/Cu interfaces regardless of the passage of electric current, but the growth of the intermetallic compound layer was enhanced by electric current at the anode and inhibited at the cathode; in comparison with the no-current case. A kinetic model was presented, based upon Cu mass transport in the sample, in order to explain the growth rates of intermetallic compounds at the anode and cathode. The growth of an intermetallic compound at the anode obeyed a parabolic growth rule, and it was proposed that the back-stress induced in the intermetallic compound played a significant role. The model was in good agreement with experimental data.

Polarity Effect of Electromigration on Kinetics of Intermetallic Compound Formation in Pb-Free Solder V-Groove Samples. H.Gan, K.N.Tu: Journal of Applied Physics, 2005, 97[6], 063514 (10pp)