Investigation Of Intermetallic Compounds In Sn-Cu-Ni Lead-Free Solders

Abstract

Interfacial intermetallic compounds (IMC) play an important role in Sn-Cu lead-free soldering. The size and morphology of the intermetallic compounds formed between the lead-free solder and the Cu substrate have a significant effect on the mechanical strength of the solder joint.In the soldering process of Sn-Cu alloys, Cu 6 Sn 5 intermetallic compounds are formed. The complex structural behaviour of Cu 6 Sn 5 IMC is temperature-and composition-dependent and it is long since subject to scientific research. The Cu 6 Sn 5 phase basically exists in two crystal structures: hexagonal η-Cu 6 Sn 5 (at temperatures above 186 • C) and monoclinic η'-Cu 6 Sn 5 (at lower temperatures). In the presence of Ni in the solder, the η-η' transformation does not occur, therefore, the η-Cu 6 Sn 5 phase remains stable.In this study the role of Ni in the (Cu,Ni) 6 Sn 5 intermetallic compound in Sn-Cu lead-free solders was examined. Sn-Cu alloys with different Cu content (0.5 to 1 mass%) were modified through Ni addition. The morphology of the intermetallic compounds of the modified Sn-Cu alloys was investigated by optical microscopy (OM) and scanning electron microscopy (SEM), the IMC phases were examined with X-ray diffraction method (XRD).

Formation and Growth of Intermetallic Compounds in Lead-Free Solder Joints: A Review

“…This was due to the fact the Cu concentration in the solder grew quicker in smaller solder balls than in bigger ones. Funding: Neutron tomography studies of geopolymer ceramic used for reinforcement materials in solder alloy for a robust electric/electronic solder joint under reference No: JPT.S (BPKI)2000/016/018/019 (29).…”

“…The Cu atom in Cu 6 Sn 5 can be substituted with Ni atom, which changes the composition to (Cu, Ni) 6 Sn 5 . Nagy et al [29] elucidated the role of Ni in (Cu, Ni) 6 Sn 5 IMC in Sn-Cu-Ni. They discovered that increasing the Ni content causes the Cu 6 Sn 5 intermetallic's lattice parameters a and c to decrease.…”