[Heath] OT question on soldering flux

[G3OOU at aol.com]

Hi Rob
 
I use a rosin based solder and prefer not to leave any flux on a PC  board 
post assembly. Rosin flux is only active at high temperatures but the  
residues can cause problems in the long term if the board is left in a damp  
environment.
 
I clean my homebrew PC boards with alcohol, cellulose thinners or similar  
(extreme care is needed here with polystyrene based components), dry them 
and  then cover the solder side with a clear polyurethane varnish for long 
term  protection. Commercial PCBs can have a solder resist that does the same 
function  as the varnish but should still be cleaned of flux residues.
 
I would never consider using a liquid flux on a PCB but see the next  
paragraph.
 
Plumbers flux is very useful for tinning badly corroded parts  contacts but 
MUST be completely removed before final assembly or the  residue will cause 
severe oxidation of any metal parts. You only have to look at  a copper 
water pipe left with flux residue a year later to see the growth  of a green 
oxide.
 
73

Bob

Bob F Burns G3OOU,  G-QRP 6907, @BobFBurns
Crystal Palace Radio & Electronics Club: _www.g3oou.co.uk_ 
(http://www.g3oou.co.uk/) 
Technical web site: _www.qsl.net/g3oou  

 
In a message dated 08/09/2015 18:49:13 GMT Standard Time,  
rsmyers at rogers.com writes:

OT  question on soldering since it looks like I may soon be doing a bit more
of  that than usual.

I see No Clean Flux liquid for sale at a local  electronics shop.  It sounds
better than flux where cleaning is  required, but I see Rosin Flux for sale
right beside it, so there must be  some trade off.

Is there much of a difference?

Thanks,
--  Rob

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