Don is exactly right about this. When I was at HP/Agilent, the company
directive was generally not to try to clean the rosin with alcohol.
(Rosin-core solder was used only in rework.) The rosin contains an acid
to help with the soldering, but the acid is locked up inside the rosin
where it does no harm. Once you dissolve the rosin with the alcohol it
spreads out and can cause leakage paths between connections. Just leave
the rosin there; it does no harm
HP did clean production boards after going through the wave solder
machine. But that used a water-soluble flux and the cleaning process
was thorough enough to completely remove all traces of flux. That's
basically not possible using alcohol and cotton swabs on rosin.
Alan N1AL
On 7/14/2021 5:20 PM, Don Wilhelm wrote:
When I have cleaned boards with IPA or other cleaners, I apply the IPA
only in a small spot with a q-tip and then blot it with a paper towel
to help dry it - do not flood the board.
I generally do not recommend cleaning boards, solder flux is
non-conductive and will normally not cause a problem.
I only clean when the solder flux residue is really nasty as might
occur with Kester 44 solder.
Use of a solder with a mildly reactive flux (Kester 385) will reduce
the need for cleaning the board - there is almost no residue.
If you do choose to clean the board, make sure your cleaning work is
complete. While solder flux is non-conductive, the flux plus the
cleaner may be conductive leading to resistive leakage paths. If you
can see any white stuff on the board, you have not done a complete job.
73,
Don W3FPR
On 7/14/2021 6:41 PM, Peter Eijlander (PA0PJE) wrote:
Yes Jerry, isopropyl alcohol does this!
I once cleaned a working print of a GPS receiver with isopropyl
alcohol and it stopped working. Letting it be and trying it again
next day turned out it worked perfectly again.
From then on I leave a PCB to rest after cleaning to have the IPA
dry out completely...
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