Julie,

 Ok, Dollars to Doughnuts. Let's say I get some of the Kester 985M. What is the easiest way to test if heat deactivation is required?

 As someone who ran a wave machine for years I know darn well that there is a lot of flux that never gets near the wave. The foam and spray systems will get flux up on ICs and into connectors, everywhere. Preheaters I have used were always facing only the board bottom.

 I am going to follow up with Kester. I still question how much "Deactivation" can be accomplished with heat as so much flux goes into so many places. I still cannot believe this stuff requires heating to be as good as indicated on the data sheet, but I could be wrong. I think it comes in pens, I will get one.

Thanks again for your time.
Bob K.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Julie Silk
Sent: Thursday, April 26, 2012 7:25 PM
To: [log in to unmask]
Subject: Re: [TN] 4 Questions: No Clean vs flux Deactivation. Possible Hogwash ???

The wave solder will deactivate the acids in this liquid wave-solder flux (and in my last message I meant to say deactivate the flux, not deactivate the solder!), so unless the flux gets sprayed in a place where it won't see a decent amount of heat, there's no issue with this flux.  Yes, it can leave a mess, but usually it's a thin layer of flux residue that is hard and not tacky, and has a high SIR.  When used in the right process!  I also like the clean look of watersoluble fluxed boards, but there are times when these will get trapped under low/no clearance parts and cause leakage paths.  Also, there are certain parts that can't tolerate exposure to halide-containing acid fluxes, so those need a different flux selection.  Another way-back experience was with RMA flux residues during a harsh condensing test -- it acted like a conformal coating, preventing the metal from shorting under condensation.  Wouldn't be a guarantee, but it decreased the shorting, didn't increase it.  


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