Thermodynamic Study of the Phase Equilibria in the Sn-Ag-Bi-Cu Quaternary System

Abstract

The phase equilibria in the Sn-Ag-Bi-Cu quaternary system have been studied experimentally and using thermodynamic calculations. The phase boundaries in some vertical sections of the Sn-Bi-Cu and Sn-Ag-Bi-Cu systems were determined using differential scanning calorimetry. The experimental values of the thermodynamic parameters were used in the calculations of the phase diagrams for the quaternary system. Thermodynamic evaluation of the Sn-Bi-Cu system was performed by considering a two-phase separation of the liquid phase. The phase diagram calculations showed that the Cu-Sn-based compounds form as the primary crystals, even for low Cu concentrations, and accordingly, the melting point of the alloys rises markedly. The microstructure of the solidified alloys was observed using a scanning electron microscope. We observed that coarsened Bi particles existed alongside the Cu-Sn-based primary crystals. Based on these results, a non-equilibrium solidification process using the Scheil model was simulated and compared with the observed structures. Our calculations reasonably explain the Bi-enrichment in the final solidification zone.

Kinetics of intermetallic compound layers and shear strength in Bi-bearing SnAgCu/Cu soldering couples

“…Among the new developed lead-free solders, Sn-Ag-Cu-Bi is regarded as one with high quality and performance and can meet the requirement of electronic packaging. Researches have been reported on their property and microstructure evolution [1,2].…”

Wetting of Cu Pads by Bi-2.6Ag-xCu Alloys and Phase Equilibria in the Ag-Bi-Cu System

“…Liu and Sun, 27 based on a DTA study of 12 cross-sections, established a ternary eutectic at 531 K for 5Ag-94.5Bi-0.5Cu (at.%) and proposed the liquidus projection. The liquidus projections were calculated from extrapolated binary data by Kattner 28 and Doi et al 12 Although they used different sets of binary data, the outcomes of their calculations were close and in reasonable agreement with the data of Liu and Sun. 27 Recently, we have studied phase transitions with temperature in 24 alloys 17 characterized by fixed molar ratios of Ag to Bi (0.25, 1, 4) and varying copper content, and compared the results with transition temperatures calculated from extrapolated binary data in the SOLDERS database.…”

“…12 Over the past years, attention has been paid to thermodynamics and phase equilibria in the following ternary systems: Ag-Bi-Sn, 13 Ag-Cu-Sn, 14,15 and Bi-Cu-Sn. 16 Recent experimental information on the thermal behavior of Ag-Bi-Cu alloys 17 and the thermodynamics of liquid 18 facilitates an assessment of the thermodynamic properties of this system.…”

Thermodynamic properties of the liquid Ag-Bi-Cu-Sn lead-free solder alloys

“…Alloys based on those components are considered among others as possible materials for the lead-free solders [1][2][3][4][5]. Systematic experimental and theoretical studies of thermodynamic properties [e.g., [6][7][8][9][10][11][12][13][14] , made by the various research centers partially coordinated by the European actions COST531 [15] and MP609 [16] led to the development of complete thermodynamics descriptions of the binary and ternary systems based on those elements [e.g., [17][18][19][20][21]. Phase boundaries and chemical composition of quaternary Ag-Bi-Cu-Sn system were investigated by Doi at all [22] using differential scanning calorimetry (DSC), optical microscope and a scanning electronic microscope (TEM) while the chemical compositions were determined by energy dispersive X-ray microanalyzer (EDX).…”