Study of the Zn occupancy leading to the stability improvement for Cu6Sn5 using a first-principles approach

Phase stability and thermal expansion behavior of Cu6Sn5 intermetallics doped with Zn, Au and In

“…According to other research [27,31], the Gibbs free energy based on classic thermodynamic methods and formation enthalpy with first principles approach of Cu 6 (Sn,Zn) 5 was found to be a function of Zn content [27,31]. The proper content of Zn doped in Cu 6 Sn 5 has minimal Gibbs energy/formation enthalpy corresponding to the most stable crystal structure [3,31]. The decreasing formation enthalpy of h-Cu 6 (Sn,Zn) 5 demonstrated that h-Cu 6 (Sn,Zn) 5 was more stable than the pure Cu 6 Sn 5 [31].As summarized in Fig.…”

“…In and Zn atoms occupying Sn2 sites to replace Sn atoms is the scenario that leads to a more thermodynamically stable phase than pure h-Cu 6 Sn 5 . According to other research [27,31], the Gibbs free energy based on classic thermodynamic methods and formation enthalpy with first principles approach of Cu 6 (Sn,Zn) 5 was found to be a function of Zn content [27,31]. The proper content of Zn doped in Cu 6 Sn 5 has minimal Gibbs energy/formation enthalpy corresponding to the most stable crystal structure [3,31].…”

“…The proper content of Zn doped in Cu 6 Sn 5 has minimal Gibbs energy/formation enthalpy corresponding to the most stable crystal structure [3,31]. The decreasing formation enthalpy of h-Cu 6 (Sn,Zn) 5 demonstrated that h-Cu 6 (Sn,Zn) 5 was more stable than the pure Cu 6 Sn 5 [31].As summarized in Fig. 10, the first principles calculation suggests that Zn, Au and In additions change the crystal cell volume by substituting for Cu/Sn at specific sites.…”

“…According to recent reports [14,31], the Ni and Zn stabilization effect is caused by an energy reduction in cells and Ni developing distinct bonding to both Cu and Sn atoms in the hexagonal (Cu.Ni) 6 Sn 5 phase [14], while the hybridization between Zn-d and Sn-s states can also influence the stability of Cu 6 (Sn,Zn) 5 [31]. Fig.…”

“…However, as electronic devices usually experience thermal cycling or thermal shock during operation, the interfacial layers of solder joints, which are commonly dominated by Cu 6 Sn 5 intermetallics, require sufficient chemical and thermal stability [6,10,11,14,15,18,19,23,25,26,27,28,29,30,31]. Therefore the thermal expansion behavior of Cu 6 Sn 5 over the service temperature range is of great importance with respect to the integrity of solder joints.…”