Interfacial reactions and compound formation in the edge of PbSn flip-chip solder bumps on Ni/Cu under-bump metallization

Soldering-induced Cu diffusion and intermetallic compound formation between Ni/Cu under bump metallization and SnPb flip-chip solder bumps

“…Detailed analyses of these IMCs including related phase equilibrium were recently reported. 13,14,16 The Atomic Flux of Cu in the Joints during Heat Treatments Figure 2b, an EPMA trace-line analysis across the Ni/IMC/solder interface after one reflow, gives evidence of the presence of Cu atoms in the Ni, IMC, and SnPb solder. The atomic flux of Cu, J Cu , can be expressed as (1) where T i is the average thickness of i, W Cu in i is the concentration of Cu in i, ρ Cu is the density of Cu, N 0 is Avogadro's number, M Cu is the molecular weight of the Cu atom, and t is the heat-treatment time.…”

Inhibiting AuSn4 Formation by Controlling the Interfacial Reaction in Solder Joints

“…It was evident that the Ni 3 Sn 4 was the primary candidate of IMC formation during the initial reflow at the solder/Ni-based UBM joint. [30][31][32][33][34] Nevertheless, the difference of atomic radius between elements was less than the limit proposed by the Hume-Rothery rule, indicating that an extensive solid solubility of one metal in another only occurs if the radii of the metals differ by less than 15 %. 35 As a result, Cu in Cu 6 Sn 5 and Ni in Ni 3 Sn 4 could be substituted by Ni and Cu, respectively.…”

“…This phenomenon was also discussed in the literature. 24,[30][31][32][33][34][36][37][38][39][40] The maximum solubility of IMCs should be associated with the most thermodynamic stable one of an ordered multinary solution phase. In general, the Gibbs free energy of an ordered multinary solution phase is described by: [25][26][27][28][29] …”

Isothermal solid-state aging of Pb–5Sn solder bump on Ni/Cu/Ti under bump metallization

“…The application of UBM plays an important role and the interfacial reactions between UBM and solders are considered as a significant issue in the reliability evaluations of flip chip solder joints. Numerous efforts have been made on the study of the solder/UBM interfacial reactions, and the related results can be easily found in the literatures [2][3][4][5][6][7][8][9][10][11][12][13][14].…”