[Elecraft] OT: Another quick question about solder...

[Mel Farrer]

A couple of additional comments.  

Sometimes, if the soldering isn't perfect, traces of the water soluible flux will remain trapped in the via.  This leads to premature failure of the via, primarily in multi-layer boards.  In the automated system of assembly this is very rare, but does happen as dissecting a failed PCB has revealed.  In otherwords, don't use it at home, you can't control the variables.

Lastly, avoid trying to do any additional cleaning of the vias other than a solder wick or suction device,  The actual via metal thickness is VERY thin.  Any rough treatment will lead to cracks in the via and potential failure down stream.  

>From one who is long in the tooth.

Mel, K6KBE 

--- On Tue, 8/18/09, Ron D'Eau Claire <ron at cobi.biz> wrote:

From: Ron D'Eau Claire <ron at cobi.biz>
Subject: Re: [Elecraft] OT: Another quick question about solder...
To: elecraft at mailman.qth.net
Date: Tuesday, August 18, 2009, 1:19 PM

Eric, WA6HHQ wrote: 

Our primary concern is with the water-soluble flux solder, which leaves 
a conductive residue on hand soldered boards.

-------------------------------------------

Also some water-soluble fluxes remain corrosive at *room temperature* until
they are removed from the board, and it's *hard* to get them completely off
without special facilities. The result is a board that will slowly
disintegrate as the traces are eaten through, becoming intermittent and
eventually failing altogether weeks or months after the flux was used. 

These fluxes are designed for automated soldering facilities were the boards
undergo a powerful machine washing right after soldering that removes all
the flux. But brushing at home or even washing in the sink won't do it. (I
know one fellow who said he successfully removed the flux by running the
boards through his dishwasher, but I'd not try it. Rosin flux simply works
too well to go through all that even if it does work and even if the board
survives the dishwasher.)

Ron AC7AC


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