Optimal phosphorous content selection for the soldering reaction of Ni-P under bump metallization with Sn-Ag-Cu solder

Abstract

Nickel plating has been used as the under bump metallization (UBM) in the microelectronics industry. The electroplated Ni-P UBM with different phosphorous contents (7 wt.%, 10 wt.%, and 13 wt.%) was used to evaluate the interfacial reaction between Ni-P UBM and Sn-3Ag-0.5Cu solder paste during multiple reflow. (Cu,Ni) 6 Sn 5 intermetallic compounds (IMC) formed in the SnAgCu solder/Ni-P UBM interface after the first reflow. For three times reflow, (Ni,Cu) 3 Sn 4 IMC formed, while (Cu,Ni) 6 Sn 5 IMC spalled into the solder matrix. With further increasing cycles of reflow, the Ni-Sn-P layer formed between (Ni,Cu) 3 Sn 4 IMC and Ni-P UBM for Ni-10wt.%P and Ni-13wt.%P UBM. However, almost no Ni-Sn-P layer was revealed for the Ni-7wt.%P UBM even after ten cycles of reflow. In consideration of the wettability of Ni-P UBM, the interfacial reaction of SnAgCu/Ni-P, and dissolution of Ni-P UBM, the optimal phosphorous selection in Ni-P UBM was proposed and also discussed.

Effects of graphene nanosheets on interfacial reaction of Sn–Ag–Cu solder joints

“…This linear relationship suggests that the growth of IMC layer in soldering process is controlled by the diffusion mechanism and the thicker IMC layer of composite solders shows that its growth is restrained by the addition of GNSs. Because the formation of interfacial IMC was controlled by diffusion mechanism, so its growth process can be described by an experienced formula [20,21]:…”

Effects of Cu contents in flux on microstructure and joint strength of Sn–3.5Ag soldering with electroless Ni–P/Au surface finish

“…On the other hand, (Cu, Ni) 6 Sn 5 is preferentially formed if the Cu concentration in the Cu-bearing solder is above 0.5 wt.% [13][14][15][16][17][18]. For a medium Cu content, both (Ni, Cu) 3 Sn 4 and (Cu, Ni) 6 Sn 5 have been observed to form at the joint interface [13][14][15][19][20][21] These results indicate that the concentration of Cu in a solder greatly influences the formation of a variety of interfacial intermetallic compounds between the solder and a Ni-based surface finish. Thus, it is expected that the Cu compound content in a flux also has some impact on the growth of both interfacial IMCs and a P-rich layer at a solder joint with an ENIG surface finish.…”

Diffusion Barrier Characteristics of Electroless Co(W,P) Thin Films to Lead-Free SnAgCu Solder

“…7,8 Feasibility of electroless Co(P) and Co(W,P) to the diffusion barrier to PbSn solder was also reported. 9,10 The researches regarding of the available barrier materials and Pb-free solders, e.g., the interactions of Ni-base barriers and Pb-free solders, [11][12][13][14][15][16][17][18][19][20][21] are rather flourishing in recent years. However, the diffusion barrier characteristics of electroless Co(W,P) to Pb-free solders are less investigated.…”