Investigation of enhanced solder wetting in 63Sn/37Pb and Sn-Ag-Cu lead free alloy

Enhanced or equivalent solder paste wetting on organic solderability preservative (OSP) circuit boards in 63Sn/37Pb and 96.5Sn/3.0Ag/0.5Cu at lower peak temperature and time above liquidus (TAL) has been published previously. These results are contrary to common belief and practice in microelectronics soldering. Microelectronics and general metal wetting literature will be reviewed to generate hypotheses about the cause of the enhanced or equivalent solder wetting. The former wetted area experiments were conducted using design of experiments (DOE) techniques and now analysis outside of the DOE will be conducted to test the new hypotheses and advance the knowledge of solder wetting. Industry relevant manufacturing equipment, materials and processes were used. After detailed analysis, the enhanced or equivalent wetting appears to be unique to the proprietary flux chemistry.