abstract |
The present invention discloses a metallization layer structure for flip chip package, which comprises an UBM layer formed on a metal pad, whereby a fine-quality tin-based solder ball can be formed on the metal pad. The UBM layer is a NiZnP layer formed via the reduction and oxidization of a solution containing nickel sulfate (Ni 2 SO 4 ), zinc sulfate (ZnSO 4 ), sodium dihydrogen phosphite (NaH 2 PO 2 ), sodium citrate dihydrate (Na 3 C 6 H 5 O 7 -2H 2 O), and ammonium chloride (NH 4 Cl). The present invention replaces the conventional Au/Ni—P dual-layer structure. Therefore, the present invention can decrease the complexity of the process and reduce the cost. Further, the metallization layer structure of the present invention is tough, hard to peel off and highly corrosion-resistant. |