Impact of Ni concentration on the intermetallic compound formation and brittle fracture strength of Sn–Cu–Ni (SCN) lead-free solder joints

Effect of Ni on the Formation and Growth of Primary Cu6Sn5 Intermetallics in Sn-0.7 wt.%Cu Solder Pastes on Cu Substrates During the Soldering Process

“…Electron dispersive X-ray spectroscopy (EDS) mapping was conducted to observe the Ni and Cu distribution. IMCs are known to be finer needle-like shaped Ƞ-Cu6Sn5 [7] with a larger grain boundary area and provide a large area of molten solder in contact with the initial interfacial IMC. In comparison with Sn-0.7wt%Cu solder, scallop shaped Ƞ-Cu6Sn5 interfacial IMCs are known to form [7] with a smaller grain boundary area in contact with molten solder.…”

“…In addition, Yoon et al [15] had investigated the growth of interfacial Cu6Sn5 in Sn-Cu-Ni solders after thermal ageing and identified that the interfacial intermetallic compound (IMC) activation energy was considered low compared to the activation energy of interfacial IMC in binary Sn-Cu solders. In another study, Yang et al [7] had reported that with Ni additions to Sn-0.7wt%Cu the growth of Cu3Sn interfacial IMC was suppressed which also resulted in the formation of fine needle-like (Cu,Ni)6Sn5 at the solder/substrate interface. In addition, the reported effects of small additions of Ni in Sn-0.7wt%Cu solder alloys have included better fluidity [14,16], alterations to the eutectic composition and promotion of a near eutectic Sn-Cu6Sn5 microstructure, stabilisation of the hexagonal high temperature phase of Cu6Sn5 [17], and suppression of cracking in Cu6Sn5 solder joints formed between Sn-0.7wt%Cu solders and Cu substrates [18].…”

“…Due to this disadvantage, many researches has been undertaken on the micro-alloying effects of several elements in the Sn-Cu solder system including Ni [4][5][6][7][8], Zn [6], Bi [9], In [10] and Al [11,12]. These micro-alloying attempts have been made to improve the mechanical properties of a solder joint.…”

Influence of bismuth on the solidification of Sn-0.7Cu-0.05Ni-xBi/Cu joints

“…Furthermore, the dilute Ni addition has been demonstrated to significantly affect the intermetallics that form during soldering. For example, Ni stabilises the high temperature hexagonal polymorph of Cu6Sn5 at low temperature [9,10], and Sn-0.7Cu-0.05Ni/Cu joints have a fine-grained (Cu,Ni)6Sn5 interfacial layer [11,12] and suppressed growth of the Cu3Sn interfacial layer [11,[13][14][15][16]. It has been further demonstrated that additions of Ni to Sn-0.7Cu solder result in considerable refinement of the Cu6Sn5 primary crystals in the solder bulk, decreasing their size and increasing their number density [17].…”

Influence of Ni on the refinement and twinning of primary Cu6Sn5 in Sn-0.7Cu-0.05Ni

“…Ni is increasingly added to Sn-Ag-Cu-X [2] and next-generation solder compositions [3,4]. The addition of Ni significantly affects the intermetallic reaction layers between the solder and copper [5]; a ~500 ppm Ni addition suppresses the formation of the Cu3Sn layer [6][7][8][9] and results in a finer and smaller (Cu,Ni)6Sn5 layer after reflow [8,10].…”