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As a literature review article, the purpose of this paper is to highlight the intricate interaction and correlation between the interconnection microstructure and the failure mechanism. It is therefore critical to summarize all the challenges in understanding solder solidification of interconnections.

Literature review.

Solidification of solder interconnections is therefore critical because it is the process during which the solder interconnection is formed. The as‐solidified microstructure serves as the starting point for all failure modes. Because of the miniaturization of electronics, the interconnection size decreases continuously, already to such a range that solder solidification takes place remarkably differently from the bulk ingot, on which solidification studies have been focused for decades. There are many challenges in understanding the solidification of tiny solder interconnections, including the complex metallurgical system, dynamic solder composition, supercooling and actual solidification temperature, localized temperature field, diverse interfacial IMC formation, and so on, warranting further research investment on solder solidification.

This paper provides a critical overview of the concerns in solidification study for lead‐free solder interconnection. It is probably an article initiating more attention towards solidification topics.

To determine the Coffin‐Manson (CM) equation constants for fatigue life estimation of Sn‐8Zn‐3Bi solder joints, since Sn‐8Zn‐3Bi solder has a melting temperature of around 199°C which is close to that of the conventional Sn‐Pb solder which has previously been used in the electronics assembly industry.

Three dimensional finite element (FE) simulation analysis was used for comparison with the experimentally measured data and to determine the CM constants. Low cycle fatigue tests and FE simulations were carried out for these lead‐free solder joints, and eutectic Sn‐37Pb solder was used as a reference.

The CM equation for Sn‐8Zn‐3Bi solder joints was fitted to the lifetimes measured and the shear strains simulated. The constants were determined to be 0.0294 for C, the proportional constant, and for the fatigue exponent, β, −2.833.

The CM equation can now be used to predict the reliability of Sn‐8Zn‐3Bi solder joints in electronics assembly and the knowledge base for the properties of the Sn‐Zn solder system has been increased.