Effect of Soldering Temperature on Wetting and Optical Density of Dip Coated Sn and Sn-3.5Ag Solders

The effects of soldering temperature on wetting characteristics and optical density of dip coated Sn and Sn-3.5Ag solders on Cu substrate were investigated. The wettability of solders was assessed by the wetting balance tester. The temperature of the solder bath varied in the range of 250-300°C. With the increase in temperature, a slight decrease in the surface tension of solders was noticed. The wetting tests demonstrated an increased solderability of pure Sn with temperature compared to Sn-3.5Ag solder. The optimum solderability of each solder was obtained at 270°C. The optical density of both the solders was also found to be highest at 270°C. It is reported that wettability and optical density of a solder are related to each other and can be tailored by varying the soldering temperature.