Intermetallic formation induced substrate dissolution in electroless Ni(P)-solder interconnections

Abstract

The effect of minor transition metal (TM) additives of Ni, Co, or Zn on the interfacial reactions of the solder joints between Sn–Ag–Cu (SAC) solder and the Cu/Ni(P)/Au substrate was investigated, especially subsequent to multi-reflowing. (Cu,Ni)6Sn5 formed at the interface of all the joints except that of SAC–Ni, of which the interfacial compound was (Ni,Cu)6Sn5. The interfacial compounds of the SAC–Co and SAC–Zn contained a small amount of alloying elements of less than 3 at.%. Two P-rich layers, Ni3P and Ni–Sn–P emerged at the interface of the SAC joints. Nanoindentation analysis indicates that the hardness and Young’s modulus of these two phases were slightly higher than those of the Ni(P) substrate, which were in turn much greater than those of the Cu–Ni–Sn compounds. Worthy of notice is that with TM additions, the Ni–Sn–P phase between Ni3P and interfacial compounds was absent even after 10 reflows. For the SAC–Co joints, the growth of Ni-containing intermetallic compounds within the solder gave rise to the excess Ni dissolution, which caused a discrete Ni3P layer and over-consumed Ni(P) substrate underneath the grooves in-between (Cu, Ni)6Sn5 scallop grains at the interface. This phenomenon is presented for the first time, and the mechanism is proposed in this study.

Alloying modification of Sn–Ag–Cu solders by manganese and titanium

“…Also, it has been reported that for the joints of Ni-doped Sn-Ag solders and Cu, interfacial IMC was irregular (Cu,Ni) 6 Sn 5 rather than scalloped Cu 6 Sn 5 and did not show an observable change in thickness after long time aging [6]. Song et al [7] found that TM additions can effectively suppress the formation of the Ni-Sn-P phase between Ni 3 P and interfacial compounds in SAC solder joints with Cu/Ni(P)/Au substrate.…”

Interfacial Reactions and Microstructures of Sn-0.7Cu-xZn Solders with Ni-P UBM During Thermal Aging

“…Song et al compared the effect of a minor addition of Co, Ni, and Zn on interfacial reactions in Sn-3.0Ag-0.5Cu and Ni-P, but in their work more emphasis was placed on Co and Ni than on Zn. 12 Kang et al reported the effects of minor addition of Zn on the interfacial reactions of Sn-3.8Ag-0.7Cu with Cu versus Ni-P, but with more focus on the interfacial reactions with Cu UBMs. 10 In this study, the effects of minor addition of Zn on the interfacial reaction of Sn-0.7Cu with electroless Ni-P UBM during thermal aging at 150°C were investigated.…”

Thermodynamic assessment of the Sn–Ag–Co system and solidification simulation of the ternary alloy

“…In order to improve the properties of solder alloys, many works have been carried out on the alloying and processing methodology. For instance, the effect of solidification process [12][13][14][15] and alloying element such as Co, Ni [16][17][18][19][20][21][22][23] on the microstructure has been investigated extensively. It was reported that addition of Co into the Sn-Ag solder could result in the formation of new compound and refinement of grain size, as well as the suppression of under-cooling [19].…”