Behavior of Au and Pd and the effects of these metals on IMCs in Pd-Au-coated copper wire

Research Progress of Palladium-Plated Copper Bonding Wire in Microelectronic Packaging

“…Therefore, the formation rate of Cu-Al IMCs is much slower than that of Au-Al, approximately 1/10 of Au-Al, and the thickness is very thin [ 53 , 54 , 55 ]. Early studies have shown that the Cu-Al IMCs of bare Cu wire is hard and brittle [ 56 , 57 , 58 ], but in the Cu-Al IMCs of PdCu wire, because the electronegativity difference between Pd and Cu is very small (Pd is 2.2, Cu is 1.9) [ 59 , 60 ], it is easy to form a solid solution with a face-centered cubic structure, so the Cu-Al IMCs of PdCu wire has better ductility and a slower growth rate [ 61 ]. It has been reported that Cu-Al IMCs in PdCu wire bonding is thinner than that in bare Cu wire bonding [ 62 ], because Pd can slow down the growth rate of IMCs in PdCu wire bonding [ 43 , 63 , 64 , 65 , 66 ].…”

Copper Wire Bonding: A Review

“…They also found that a faster IMC growth rate led to accelerated crack formation. Hyun-Woong Park et al [ 63 ] studied the effects of Pd and Pd-Au coatings on Cu wire bonding. The results showed that noble metal coatings formed a fully solid solution at the Cu-Al bonding interface, potentially impeding the diffusion of Cu-Al IMCs, especially at the Cu 9 Al 4 IMC, which may delay the IMC growth rate [ 64 ].…”