[Elecraft] K2 - Cleaning a completed PC board

[Don Wilhelm]

  Stan,

Do NOT attempt to remove the flux - it is not conductive and will cause 
no problems, even though it may look slightly "messy".
In fact, attempts at removing flux can result in unanticipated 
problems.  If the flux residue plus solvent gets under connector headers 
or relays, or even ICs, it will not be completely removed and the 
residue left in those places can later make conductive paths where they 
should not be.  I did work on one K1 that had been completely ruined by 
an attempt at removing the flux.

If you must clean a board, do it in small areas - do NOT flood the board 
with the solvent (yes, use de-natured alcohol, acetone can etch plastic 
components) - apply the solvent sparingly in a small area at a time, and 
blot it off with a paper towel.  Alcohol attracts water from the air 
rapidly, and the reduced temperature of the board caused by rapid 
evaporation will cause the water to condense on the board - wipe it up 
too, but do not apply power until it has completely dried.
If you feel you must remove the flux, build up a small board (like the 
RF Probe from the parts provided in the K2 kit), and practice your flux 
removal technique on that first so you know what to expect.

If you want to avoid a large flux residue, use a solder with a mildly 
reactive flux, such as Kester 285.  While Kester 44 is much better know, 
it has a highly reactive flux and leaves much more residue than the 
mildly reactive flux.  Save the highly reactive flux for soldering jobs 
that have noticeable oxidation on the surfaces.

73,
Don W3FPR

On 9/8/2010 1:43 PM, stan levandowski wrote:
> I've been told that it is good practice to clean a completed PC board
> with either acetone or denatured alcohol and a small toothbrush.
>
> I could not bring myself to do this when I completed my KX1 - it just
> seemed (at least to me) somewhat risky to be brushing a liquid with a
> nylon toothbrush all over a populated board.
>
> Now I'm faced with the same issue as I begin my K2.  I want to do
> "everything right" because this K2 is going to be my  "baby" -- but.....
>
> So I am asking for some opinions on just what the risk/benefits are and
> perhaps to get some idea as to whether this is really a practical and
> useful process or a "purist" finishing touch that returns marginal bang
> for the buck.
>
>
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