Suppressing Ni3Sn4 formation in the Sn–Ag–Cu solder joints with Ni–P/Pd/Au surface finish

Interfacial reactions of Pb-free solders with Au/Pd/Ni/brass multilayer substrates

“…There was an obvious grain ripening phenomenon in the IMC at the interface when the reaction time was increased. This result is similar to that in the SAC/Au/Pd/Ni/Cu [14], SAC/Au/Ni/SUS 304 [24], and Sn-Ag-Cu/Ni [17] couples. Again, the Cu 3 Sn phase was not formed at the interface.…”

“…An Au/Pd/Ni multilayer structure is commonly electroplated onto a metallic substrate surface to improve the joint reliability and wettability between the solder and substrate. Numerous studies have reported on the interfacial reactions of Pb-free solders with Au/Pd/Ni/metallic substrates [14][15][16][17][18][19][20][21][22][23][24][25][26]. However, research on the interfacial reactions between the solder and Au/Pd/Ni/brass systems is lacking.…”

Comparison between SAC405 Lead-Free Solders and EN(P)EPIG and EN(B)EPIG Surface Finishes

“…Since PdSn 4 IMC is not as stable IMC as Ag 3 Sn IMC, Pd will combine with Ni and Cu elements where Ni is also dissolved from Ni-P layer and Cu from solder alloy in the same time to form (Cu,Pd,Ni) 6 Sn 5 or (Ni,Pd,Cu) 3 Sn 4 depending on the availability of Ni or Cu atom during interfacial reaction. This is in good agreement with Tseng et al [12] and Azmah [6]. Moreover, the presence of the thin Pd layer in the ENEPIG finish may have suppressed the growth of the interfacial IMC layer and the consumption of the Ni(P) layer, resulting in the superior interfacial stability of the solder joint during prolonged reflowing at 260ºC [8].…”

Interconnection: The Joint

“…Pd may refi ne the grain structure of (Cu,Pd) 6 Sn 5 and also inhibit its grain growth [ 99 ]. The refi nement of grain size may be attributed to lattice strain arising from the different atomic radii of Cu (128 pm) and Pd (137 pm), which causes slower grain growth in Cu 6 Sn 5 [ 100 ].…”