Prediction of interface reaction products between Cu and various solder alloys by thermodynamic calculation

Formation and Growth of Intermetallic Compound Cu6Sn5 at Early Stages in Lead-Free Soldering

“…On the other hand, while the e phase (Cu 3 Sn) also has a positive driving force for nucleation, the magnitude of this driving force is smaller, and the expected nucleation rate for this phase during early stages would be much smaller than for the g phase. 19 This seems to be corroborated by experimental observations.…”

“…Most research seems to suggest that, at the very early stages of the soldering reaction, the g phase precipitates first. Lee et al 19 compared the driving forces for the precipitation of the two different Cu-Sn phases at the metastable solid Cu/liquid Sn interface. Under these local metastable equilibrium conditions, the g phase has the largest driving force for precipitation.…”

“…If one assumes that other contributions (e.g., interfacial energies) to the activation barrier for nucleation are comparable between the two phases, the larger thermodynamic driving force would explain the observed precipitation sequence. 19 After the precipitation of the g phase, the precipitation of the e phase at the g/Cu substrate interface becomes thermodynamically possible, and it is thus usually observed at later stages of the soldering reactions. 19 Earlier works have focused on experimental characterization of the late stages of growth and coalescence of g and e phases during lead-free soldering reactions between Sn and Cu.…”

“…19 After the precipitation of the g phase, the precipitation of the e phase at the g/Cu substrate interface becomes thermodynamically possible, and it is thus usually observed at later stages of the soldering reactions. 19 Earlier works have focused on experimental characterization of the late stages of growth and coalescence of g and e phases during lead-free soldering reactions between Sn and Cu. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] More recently, several groups have investigated the formation of the g phase at the early stages of soldering reactions.…”

Prediction of Intermetallic Compound Formation Sequences in Pseudo Binary Diffusion Couples: Experimental Examinations for (Sn-<i>x</i>Zn)/Cu (<i>x</i> = 2, 5, 10, 15, 20 and 25 mass%) by a Kinetic Model with Thermodynamic Data Using MDR Diagram

“…For instance, ¾-CuZn 4 is predicted as a major phase at (eutectic Sn-8.8 mass%Zn)/Cu diffusion couple, 8) but £-Cu 5 Zn 8 is observed as the first phase or ¾-CuZn 4 cannot be seen from experimental results in the literature. 8,10) Hence, there have been several attempts using above thermodynamic calculations to predict the first intermetallic compound phase or intermetallic compound formation sequence by comparing driving forces of homogeneous nucleation of intermetallic compound phases, 7,8) activation energies for homogeneous nucleation of intermetallic compound phases, 9) effective heat of formation of an intermetallic compound phase (EHF model), 11) or by applying modified Jonson-Mehl-Avrami-Kolmogorov kinetic equation for precipitation.…”