Abstract
The growth mechanism of intermetallics between solders and metallized substrates, after thermal aging, are investigated. The solders used in this study are unleaded Sn-Cu-Ni solder and eutectic Pb-Sn solder. The Pt-Ag/Al 2 O 3 , Cu block and the electroless Cu/Pt-Ag/Al 2 O 3 are employed as the metallized substrates. Microstructure evolution of the interfacial morphology, elemental, and phase distribution are probed with the aid of electron-probe microanalyzer (EPMA) and x-ray diffractometry. Two kinds of intermetallics, Cu 3 Sn and Cu 6 Sn 5 , are formed at the solder/Cu interface. However, for the solder/Pt-Ag system, only Ag 3 Sn is observed at the interface. The thickness of Cu 3 Sn, Cu 6 Sn 5 , and Ag 3 Sn compound layers for all solder/metallized substrate systems shows a t 0.5 dependence at 100, 125, 150 and 107°C. According to the calculated activation energy and diffusion constant, the growth rate of Cu 3 Sn and Cu 6 Sn 5 intermetallics in the electroless Cu metallized substrate is relatively higher than that for Cu block one at the range of 100°C to 170°C. However, the growth rate of Cu 6 Sn 5 and Ag 3 Sn is reduced in the Sn-Cu-Ni solder with respect to the eutectic Pb-Sn solder. On the other hand, the Sn-Cu-Ni solder system exhibits a thicker Cu 3 Sn intermetallic layer than the eutectic Pb-Sn solder after various aging times at 100°C. The thickness of Cu3Sn in the eutectic Pb-Sn solder is, however, thicker than that for Sn-Cu-Ni solder at 170°C.