Abstract
Recently, research into the factors that influence the formation and growth of intermetallic compounds (IMCs) layer in lead-free solders has piqued interest, as IMCs play an important role in solder joints. The reliability of solder joints is critical to the long-term performance of electronic products. One of the most important factors which are known to influence solder joint reliability is the intermetallic compound (IMC) layer formed between the solder and the substrate. Although the formation of an IMC layer signifies good bonding between the solder and substrate, its main disadvantage is due to its brittle nature. This paper reviews the formation and growth of IMCs in lead-free solder joints detailing the effect of alloying additions, surface finishes, aging time, aging temperature and solder volume. The formation and growth of the brittle IMCs were significantly affected by these factors and could be possibly controlled. This review may be used as a basis in understanding the major factors effecting the IMC formation and growth and relating it to the reliability of solder joints.
Highlights
Introduction published maps and institutional affilTin-lead (Sn-Pb) solder has been widely used as an interconnecting material for many years
The thickness and composition of intermetallic compounds (IMCs) greatly affected by surface finish layers
We have summarized the causes that can impact the formation and growth of intermetallic compounds (IMCs), which are recognized to constitute an important role in joint structure
Summary
The intermetallic phase might develop in the bulk solder as the main part of the eutectic phase and interfacial IMCs in a lead-free solder alloy. They hypothesized that the addition of a small amount Al into Sn-0.7Cu solder alloy helps to reduce the Cu6 Sn5 size while increasing the number of Cu6 Sn5 particles per unit volume. Mcdonald et al [18] researched the effect of trace elements addition on the morphology and size of the primary Cu6 Sn5 in Sn-4 wt.%Cu alloy with and without the addition of Ni. The investigation included additions of ppm of Pb, Ge, Ag, as well as Al. It was reported that Al influences the microstructure of the solder and refines the primary. Zn might aid in the nucleation of β-Sn, which could impact phase selection during the near-eutectic alloys formation grown at low temperatures
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