Tin/Lead Melting Point
40/60 460 degrees F (230 degrees C)
50/50 418 degrees F (214 degrees C)
60/40 374 degrees F (190 degrees C)
63/37 364 degrees F (183 degrees C)
95/5 434 degrees F (224 degrees C)
Try to combine lead free solder containing bismuth with solder containing lead and there is a possibility for the solder to reflow at reduced temperature (around or less than 100°C) ..