Review of the wettability of solder with a wetting balance test for recent advanced microelectronic packaging

This paper reviewed the wetting properties of solder for microelectronic packaging. The recent demand for high-density packaging has highlighted the need for a sophisticated and improved solder for the miniaturization of electronics. The wetting properties of molten solder on a substrate, which provides successful soldering and reliable solder joints, is one of the most critical properties for the reliability of components in electronic devices because poor wetting can degrade the reliability of the solder. Therefore, the solder must have good wettability to achieve better solderability. The most common testing method is the wetting balance test known as a Meniscograph. During a wetting test, the analysis can be conducted by calculating the wetting force between the molten solder and substrate as a function of time. In addition, the surface tension and wetting time, which are known as the zero cross time of each sample, are obtained from the respective wetting curves. This paper discusses the wetting balance test, including its principle, parameters, experimental procedure, and analysis of the result from the wetting curve. In addition, this paper introduces the recent advances in the wetting property of solder, such as a nano-reinforced composite solder through the addition of 0.05% of nano-sized La₂O₃ to the solder matrix, which has resulting in an improved wetting time.