[Elecraft] Cleaning Solder Flux, Redux

[Alan Bloom]

Another problem with cleaning flux is ionic contamination.  The 
activator in the flux, which is necessary to get the solder to stick, is 
acidic.  As long as the flux is left alone, the ionic contamination is 
trapped in the rosin where it can do no harm.  But when you dissolve it 
with alcohol or another solvent is is spread over the surface of the 
board, unless you do a VERY thorough job of cleaning it off.  That can 
cause electrical leakage between circuit nodes and potentially corrosion.

The only reason for removing flux is purely cosmetic.  When I was at 
HP/Agilent the rule in production and service was that any flux 
remaining on the board due to re-work or repair was just left in place.

Alan N1AL


On 1/1/2022 3:25 AM, CUTTER DAVID via Elecraft wrote:
> Ted
> If the residue is clear, don't bother, you might create more damage than you realise (ESD).  If the residue is brown, you've been using the wrong solder.  If you really feel the desire for aesthetics then you can can brush it with IPA, but beware ESD if there are sensitive components on board.  Also beware some components can dissolve in some cleaners, eg old style polystyrene capacitors.
>
> 73 and HNY
> David G3UNA
>
>> On 31 December 2021 at 20:52 edauer at aya.yale.edu wrote:
>>
>>
>>   
>>
>> Is there a consensus among builders of the traditional kits (K1, K2, etc)
>> about the best way to remove solder flux from a completed circuit board?
>> Some Internet sites recommend acetone, others say isopropyl alcohol. A few
>> tout their own product without saying exactly what it is.  I remember
>> reading someplace that one or the other of those will clean the flux but
>> could also cause damage by being absorbed into components.  Yes, I know this
>> is all purely cosmetic but if it can be done safely I'd like to try it on
>> the next kit.  Suggestions?
>>
>>   
>>
>> Thanks,
>>
>>   
>>
>> Ted, KN1CBR
>>
>>   
>>
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