Electromigration behavior of lead-free solder flip chip bumps on NiP/Cu metallization

• Published in: Journal of applied physics 2008-06, Vol.103 (12), p.123506-123506-5
• Main Authors: Jang, J. W., Ramanathan, L. N., Frear, D. R.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2940133

The electromigration behavior of Sn-2.5Ag and Sn-0.7Cu (in wt % ) flip chip solder joints on electroless NiP/Cu metallization at a current density of 1.3 × 10 4   A / cm 2 was studied. For Sn-2.5 Ag solder, electromigration at 115 ° C for 250 h showed a selective dissolution of Ni from the electroless NiP layer forming crystallized Ni 3 P . At 140 ° C , the damage to the NiP layer was accelerated and instability of the NiP/Cu interface was observed. For eutectic Sn-0.7Cu solder, the electromigration behavior at a higher temperature was evaluated. At 180 ° C , the NiP/Cu under bump metallurgy (UBM) started to show damage after 50 h. At 200 ° C , the entire NiP/Cu layer was damaged, and P in the NiP layer moved to the edge of the anode much faster than the other species forming CuP 2 intermetallics. NiP/Cu UBM experiences selective dissolution of Ni at lower temperatures, and the damage of the entire UBM occurred abruptly at the higher temperature.