“…Recently, much attention has been paid to the effects of impurities and alloying additions on the Cu 6 Sn 5 interfacial reaction layers between the Snbased solders and Cu substrates. [1][2][3][4][5][6] Trace elements are categorised into two groups: [6] (1) elements that show marked solubility in the Cu 6 Sn 5 solder joint layer such as Ni, Sb, Au, In, Co, Pt, Pd, and Zn, and (2) elements that are not extensively soluble in Cu 6 Sn 5 such as Ag, Fe, Bi, Al, P, Ti, S, and rare-earth elements. The role of dissolved trace additions in Cu 6 Sn 5 in determining the intermetallic layer growth and phase stability has been the subject of a range of recent studies.…”