Interfacial reactions in Au/Sn/Cu sandwich specimens

The influence of ageing on the stabilisation of interfacial (Cu,Ni)6(Sn,Zn)5 and (Cu,Au,Ni)6Sn5 intermetallics in Pb-free Ball Grid Array (BGA) solder joints

“…This result is consistent with the findings in Ref. [59][60][61], where the Au solubility in Cu 6 Sn 5 was apparently higher because the Cu ageing.…”

Phase Diagrams and Their Applications in Pb‐Free Soldering

“…A schematic diagram illustrating the composition profile through an A-B reaction couple is shown in Figure 2.25. Although the reaction couple is not in thermodynamic equilibrium, the local equilibrium condition usually holds at the interfaces [11,28,33,66,74,85]. When the local equilibrium condition is followed, the kinds and compositions of the IMCs can be determined from the phase diagrams.…”

“…However, for ternary or higher-order systems, there are diverse possibilities of reaction and solidification paths. An isothermal section of phase equilibria in a ternary system is a useful tool for illustrating interfacial reactions at a binary solder/substrate joint [11,28,33,66,74,85]. It must be mentioned that interfacial reactions and the IMC formation are not only governed by thermodynamics but also kinetics, and it is risky to predict the interfacial reactions using phase diagrams alone.…”

“…Au bump is used in flexible electronics, and Au finish is important for oxidation prevention. The interfacial reactions in the couples with Au/Sn/Cu sandwich structure have been examined [83][84][85]. Figure 2.38 shows the metallographic observations for Au/Sn(32 mm)/Cu couple reacted at 210 C for 10 min, and the reaction path can superimpose with the Sn-Au-Cu isothermal section, as shown in the Figure 2.39, which can be described as Au/AuSn/AuSn 2 /AuSn 4 / (Cu,Au) 6 Sn 5 /Sn/(Cu,Au) 6 Sn 5 /Cu 3 Sn/Cu.…”

Electronic structure of Au-Sn compounds grown on Au(111)

“…[14][15][16] Interdiffusion in Au/Sn thin films has been investigated by other groups, who reported formation of Au 5 Sn, AuSn, AuSn 2 , AuSn 4 compounds at the interface depending on the growth conditions and film thickness. 12,13,[17][18][19][20][21][22] In fact, intermixing at the surface is also expected from the Au-Sn binary phase diagram that shows high miscibility in the bulk and different intermetallic compounds have been reported. 23 The Au-Sn alloys have been reported in literature to be non-toxic soldering materials with good bonding characteristics and these are widely used in advanced electronic circuits as well as in optoelectronic devices.…”