Rosin core and no clean flux pen

Thread Starter


Joined Sep 20, 2009
Hello all,

If I'm using rosin core 63 37 solder is it ok to use a no clean flux pen or should I get a rosin flux pen?

Thread Starter


Joined Sep 20, 2009


Joined Jan 18, 2008
There are, of course, different flux compositions in rosin core solder. The degree of activation and chemicals used for that might make a difference. Now can you tell use which "no clean" flux you are using?

If you review the history of no-clean fluxes you will find that some versions were/are basically rosin flux with less rosin. It would seem that mixing those would be no problem. I would have concerns about using a water-based no clean flux with a rosin flux as rosin is not very soluble in water.

See this:
Low-Solids/No-Clean fluxes breakdown into a few other categories:
  • Alcohol-based, Rosin or Resin Containing;
  • Alcohol-based, Rosin or Resin Free;
  • Water -based, Rosin or Resin Free (VOC-free);
[rare occasions will contain rosin or resin]
For alcohol-based, rosin/resin free, one would need to know what agent(s) performed the functions of rosin or mildly activated rosin flux. Even then, compatibility would only be a guess.

In sum, I did not find anything directly on point. But there were some opinions.

Why not just test it?


Joined Aug 21, 2008
It depends upon the circuit and the needed performance. In many circuits flux can stay on the board but if you are worried about minute leakage currents or low noise it is a good idea to clean off the flux.