no clean flux + IPA = big sticky mess?

[djacobow]

I've been using a no-clean flux pen to assemble SMT boards, along with solder with normal rosin flux in it. They look pretty good right after with not all that much obvious flux residue. Sometimes I just leave them like that. But I've tried to clean a few with IPA.

Each time I have done this, the result has been a sticky, tacky mess, with the flux seemingly spread out but not removed. I'm holding the board vertically, using a toothbrush and what seems like a fair amount of IPA, and letting the IPA run down and off the board. I've repeated the process a few times, with fresh IPA and it gets cleaner, but not completely.

Am I doing something very wrong? Do I need to be using large quantities of IPA, like floating the board in a paint pan? If I do that, can I re-use that IPA or does it now have too much dissolved solder?

Pretty confused, actually.

[orbiter]

Try some dedicated flux cleaner instead of IPA.  IPA has a hard time with the sticky residue left over from rosin fluxes.  I use Electrolube Fluxclene.

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[djacobow]

Thanks, I'll give that a shot!

Try some dedicated flux cleaner instead of IPA.  IPA has a hard time with the sticky residue left over from rosin fluxes.  I use Electrolube Fluxclene.

[SeanB]

Best cleaner I can use is R141B, but that is frowned on these days. Just restocked with 5l, now in a can that is truly sealed and packed under vacuum. That though is going to destroy most plastics aside from IC packages. It will clean anything including markings and screenprint off boards. Works great on high impedance and PTFE standoffs though.

[wraper]

You either need paper wipes that will absorb IPA with flux dissolved or compressed air to blow it out of the board. Otherwise you are just spreading all the mess over the board. Flux don't disappear miraculously anywhere when IPA dries out.