[Elecraft] K2 - Cleaning a completed PC board

[Alan Bloom]

When I was working for HP/Agilent, the rule was that you NEVER clean a
board that way because of the risk of ionic contamination.

The rosin flux used in multi-core solder is normally the "mildly
activated" (RMA) type.  That means it includes a moderate amount of the
acid that is used to remove the oxide coating on the metal so that the
solder can adhere.

Left-over flux on a board is not a problem because the acid is bound up
in the rosin where it can do no harm.  However, if you melt the rosin
with alcohol or some other solvent, the acid is spread out over the
surface of the board.  It is nearly impossible to get 100% of it off, no
matter how many times you go over it with the Q-tip.

The resulting ionic contamination can cause corrosion and, in the
presence of humidity, creates an electrical leakage path between nearby
traces.

The flux that they used in production was a water-soluble (non-rosin)
type which, while quite corrosive, could be completely removed in the
automated board-cleaning machine.  Rosin flux was used in the re-work
stations but the rule was you did not attempt to clean it off.

Al N1AL


On Wed, 2010-09-08 at 13:43 -0400, 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.
> 
> Thanks for any insights,
> 
> 
> Stan Levandowski WB2LQF
> HF QRP CW -- Doing more with less for over 50 years!
> QCWA #35038   OOTC #4558   NAQCC #4740   SKCC #6488   FISTS #(Pending)
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html