WS300 is the flux system that would be used for a lead-free alloy applications where the circuit assembly will have the flux residues washed off with water. Again, the WS300 product could be left uncleaned after reflow for up to 3 days. The WS300 also offers the same level of humidity resistance as the WS200 (pass slump test of 8 hours at 25°C/RH 95%). It also provides 4 hour abandon/pause time and 24 hour tack time.