Abstract: It is believed that reaction products in the interface between solder and substrate have great effects on mechanical properties and reliability of the solder/substrate joint. Based on the calculations of metastable phase equilibria between the solder and the substrate and the comparison of the driving forces of formation of individual intermetallic compounds, a thermodynamics method was used to predict the formation sequence of the intermetallic compounds during the interfacial reaction period. This method was applied to the interfacial reaction of Sn-3.5%Ag/Cu, Sn-25%Ag/Cu, and Sn-3.5%Ag/Ni solder/substrate systems. In addition, by using Scheil-Gulliver model, the non-equilibrium solidification of Sn-25%Ag/Cu system was modeled and the microstructure evolution was also predicted. The results from thermodynamic calculations are in good agreement with previously reported experiments.
Application of CALPHAD in soldering of electronic materials
Abstract：
It is believed that reaction products in the interface between solder and substrate have great effects on mechanical properties and reliability of the solder/substrate joint. Based on the calculations of metastable phase equilibria between the solder and the substrate and the comparison of the driving forces of formation of inpidual intermetallic compounds, a thermodynamics method was used to predict the formation sequence of the intermetallic compounds during the interfacial reaction period. This method was applied to the interfacial reaction of Sn-3.5%Ag/Cu, Sn-25%Ag/Cu, and Sn-3.5%Ag/Ni solder/substrate systems. In addition, by using Scheil-Gulliver model, the non-equilibrium solidification of Sn-25%Ag/Cu system was modeled and the microstructure evolution was also predicted. The results from thermodynamic calculations are in good agreement with previously reported experiments.
Fig.1 Isothermal section of Sn-Ag-Cu at 513 K at the first metastable stage (Liq+FCC(Ag)+FCC(Cu)) (Dashed line connects solder and substrate, dotted line is the tie line at this local equilibrium)
Table 1 Calculation of driving force (ΔG) forformation of IMC phases at 513 K forSn-3.5%Ag/Cu joint in first metastablestage between liquid and FCC(Cu)
Fig.2 Isothermal section of Sn-Ag-Cu at 513 K at the second metastable stage (Liq+FCC(Ag)+FCC(Cu)+Cu6Sn5) (Dashed line is the tie line at this local equilibrium)
Table 2 Calculation of driving force (ΔG) forformation of IMC phases at 513 K forSn-3.5%Ag/Cu joint in the second metastablestage between liquid and Cu6Sn5
Table 3 Calculation of driving force (ΔG) forformation of IMC phases at 513 K forSn-3.5%Ag/Cu joint in the second metastablestage between FCC(Cu) and Cu6Sn5
Table 4 Calculation of driving force (ΔG) forformation of IMC phases at 723 K forSn-3.5%Ag/Ni joint in the first metastablestage between liquid and FCC(Ag)
Table 5 Calculation of driving force (ΔG) forformation of IMC phases at 723 K forSn-3.5%Ag/Ni joint in the second metastablestage between liquid and Ni3Sn4
Table 6 Calculation of driving force (ΔG) forformation of IMC phases at 723 K forSn-3.5%Ag/Ni joint in the second metastablestage between Ni3Sn4 and FCC(Ni)
