Most boards today are built with no clean flux. You will sometimes see a light, white residue on the boards. Especially if they are using a selective solder machine. It is much more cost effective. Repair is done with no clean flux and no clean solder as well. Washing boards in the past 10-15 yrs has become very problematic. The equipment, the EPA, and non-wettable parts are all factors in the problem.
The chenistries and solders have come a long way in the past 20 yrs.
In China, who knows what happens. At the higher end their boards do perform very well, but with constant customer monitoring.
If smoke fluid is non-conductive and non-reactive then it shouldn't be a problem any more than any other lightweight oil.
