The influence of Ni additions on the relative stability of η and η′ Cu6Sn5

The influence of Ni and Zn additions on microstructure and phase transformations in Sn–0.7Cu/Cu solder joints

“…The main feature of the Sn-0.7Cu system with respect to solidification is the presence of the L!b-Sn + g-Cu 6 Sn 5 eutectic reaction at 227°C and on further cooling there is another significant reaction, namely the polymorphic phase transformation of the Cu 6 Sn 5 intermetallic (IMC) from the hexagonal (higher-temperature) g-Cu 6 Sn 5 to a monoclinic (low-temperature) polymorph g'-Cu 6 Sn 5 at 186°C [3][4][5][6][7][8][9][10][11][12]. This solid-state polymorphic phase transformation (without composition change) is one of the most important factors influencing the reliability of the solder joints [3][4][5][6][7][13][14][15][16].…”

Influence of bismuth on the solidification of Sn-0.7Cu-0.05Ni-xBi/Cu joints

“…Furthermore, the dilute Ni addition has been demonstrated to significantly affect the intermetallics that form during soldering. For example, Ni stabilises the high temperature hexagonal polymorph of Cu6Sn5 at low temperature [9,10], and Sn-0.7Cu-0.05Ni/Cu joints have a fine-grained (Cu,Ni)6Sn5 interfacial layer [11,12] and suppressed growth of the Cu3Sn interfacial layer [11,[13][14][15][16]. It has been further demonstrated that additions of Ni to Sn-0.7Cu solder result in considerable refinement of the Cu6Sn5 primary crystals in the solder bulk, decreasing their size and increasing their number density [17].…”

Anisotropic thermal expansion of Ni 3 Sn 4 , Ag 3 Sn, Cu 3 Sn, Cu 6 Sn 5 and βSn

“…In the case of Cu6Sn5 there is limited information on the nature of the ' transformation [42,45]. However, from the crystallographic differences between the two phases in Figure 8 it can be seen that the transformation involves the ordering of Cu atoms on the 20%-occupied Cu2hex sites and only a slight distortion in other atom positions.…”

“…Note, in Table 1, that hexagonal hP4-Cu6Sn5 data are given at 200C because this phase is only stable at >186C [31,32,42].…”