A STUDY OF LOWER SOLDER TEMPERATURE FOR LEAD FREE WAVE SOLDERING

摘要

Lead-free alloys are typically soldered at higher process temperatures than traditional tin-lead process. The higher temperature causes concerns with components, board warping, and copper dissolution. Many previous studies have shown the optimum solder temperature is in the range of 265-270 °C (509-518 ℉) for SAC 305 alloy which is higher than the range of 250-260 °C (482-500 ℉) or up to 20 °C (36 ℉) greater than the temperature traditionally used for tin-lead. Wetting balance tests at various temperatures with a copper coupon and SAC 305 alloy in this study confirm previous results. Wetting balance tests are then performed with a molten solder surfactant added to the surface of the solder. The surface active additive gathers the oxides that form when molten solder comes into contact with oxygen thus enhancing the wetting of the solder.Solderability tests are performed on an Umpire Board test vehicle at various solder temperatures to examine the wetting and identify the allowable solder temperature low limit for SAC 305. This paper examines the wetting of SAC 305 with a new process that includes a surfactant that enhances the wave soldering process thus allowing the solder temperature to be lowered with lead-free alloys.