Growth behavior of Sn-Ag-Cu/Cu intermetallic compounds in high silver series

Objective The interfacial reaction and growth kinetics of high silver series Sn-Ag-Cu during solid phase aging were studied. Methods The effects of different silver contents on the interfacial structure and interfacial growth at high temperature were investigated experimentally and numerically. In order to determine the long-term reliability of solder joints, thermal accelerated aging tests were carried out at 150 ℃ for 0 h, 100 h, 300 h, 500 h. The surface morphology, thickness and elemental composition of IMC were investigated by SEM and EDS. Results The results showed that the growth of Cu₆Sn₅ was inhibited with the increase of silver content. In the isothermal aging process, the growth kinetics of intermetallic compounds (IMC, Cu₆Sn₅+Cu₃Sn) is a diffusion control process. Cu₆Sn₅ gradually grows into Cu₃Sn. In the later aging stage, the scallop-like shape disappears, indicating that the growth mechanism has changed, and the change is stable growth in the direction vertical to the interface. Through the finite element technique, it is concluded that the thermal stress is mainly concentrated at the junction of Cu₃Sn and Cu substrate during service. With the increase of aging time, the equivalent creep strain of solder joint rises and the reliability decreases gradually. The apparent activation energies of intermetallic compound IMC (Cu₆Sn₅+Cu₃Sn) at the interface Sn-3.0Ag-0.7 Cu/Cu, Sn-3.4Ag-0.7Cu/Cu and Sn-3.8Ag-0.7Cu/Cu are 67.13 kJ/mol, 70.50 kJ/mol, 69.54 kJ/mol. Conclusion Respectively, according to arrinius formula, Sn-3.4Ag-0.7Cu/Cu is better than other solder joint components to meet the requirements of electronic components.