Seeking solder no-clean flux recommendation

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Involute

Joined Mar 23, 2008
106
My standard soldering "recipe" is Kester 245 flux cored solder with Kester 951 liquid flux. Most of my work is SMD by hand (little through-hole, no reflow). My goal is as pristine a PCB as possible after soldering, with as little post-processing as possible. Nevertheless, while Kester describes the results of 245 as "visually acceptable," there's still plenty of residue (either from the 245 or 951), most of which comes off with some mild isopropyl scrubbing with an anti-static brush. Unless I put in a lot of effort, there's still residue visible. Just wondering if someone here has a better recipe/process. Thanks.
 
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dl324

Joined Mar 30, 2015
16,839
I do most of the cleaning with 90-99% IPA and a short bristle horse hair brush and finish with an aerosol flux remover.
 

Kermit2

Joined Feb 5, 2010
4,162
The residue is dissolved flux deposited when the solvent evaporates. The alcohol dries to fast to get it all off.

To get the pristine condition you prize will require a running liquid bath of pure solvent and a work station akin to a "parts washer" like those found in an auto mechanic's workshop.

Also, some flux formulas are made water soluble, so a 90% or purer alcohol will be less effective than a 50 to 70% mix.
 

RichardO

Joined May 4, 2013
2,270
The residue is dissolved flux deposited when the solvent evaporates. The alcohol dries to fast to get it all off.

To get the pristine condition you prize will require a running liquid bath of pure solvent and a work station akin to a "parts washer" like those found in an auto mechanic's workshop.

Also, some flux formulas are made water soluble, so a 90% or purer alcohol will be less effective than a 50 to 70% mix.
I have a glass, cake baking pan that I put about 3/8" to 1/2" deep with alcohol. Soaking a PCB in that for a few minutes followed by a slight scrub with a flux brush is usually enough to do the job. When I am done, I put the used liquid into a bottle labeled "used" for using again later.

Good hint on the water in lower percent alcohol being better for water soluble fluxes.
 
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