[sdiy] washing PCB's

[Seb Francis]

Hi Brett,

How you wash the PCB, or whether you do at all really depends on what 
type of solder you are using.

If you are using 'organic' / 'water-based flux' solder then you *must* 
wash your board every hour: if you don't wash it regularly the flux gets 
difficult to remove.  If you don't wash it at all, your board and 
components will later corrode because of the water in the flux.  You can 
wash with normal warm water - no need to use special distilled water.

If you are using standard rosin flux solder then you should (in theory!) 
wash the board with the appropriate solvent.  But personally I never 
bother - as long as you are fairly minimal with the amount of solder you 
use then the flux residue normally isn't a problem .. it does have some 
electrical conductance though, so for critical circuits such as VCOs it 
can effect performance.

Personally I use organic solder for 'nice' projects and wash the PCB 
regularly (this gives a lovely shiney clean end result), but for quick 
projects I use standard solder and don't bother washing.

As for what you can wash .. it is fine to wash ICs, diodes, transistors, 
most resistors, most capacitors.  But do not wash trimmers, pots, 
wirewound resistors (e.g. some tempcos), polystyrene caps.  It's usually 
pretty obvious what you can and can't immerse in water.

Solder everything that can be washed first, then use normal solder (or 
better still 'no-clean' solder) to solder in the rest.  'No-clean' 
solder isn't very nice to use, so I wouldn't really recommend it for 
general use.

Other answers below ...

> - the tb3031 manual suggests using a soft toothbrysh etc to clean the 
> board is that safe?

Yeah, a toothbrush is ideal .. just be gentle :)

> - is the purpose just to remove the flux thats left after soldering 
> and what happens if you dont wash it off? or are there other reasons?

Depends on the type of solder .. water-based flux you absolutely must 
not leave on!  Normal flux you can get away with, but it's not so good 
for critical circuits, or for when you want the PCB to look really nice 
and shiney.

> - and finally the tb3031 is a bigger project do i need to do this for 
> smaller pcbs like ken stones etc?
>
Depends on the type of solder you use .. if you don't want to wash then 
use normal solder .. you could try using 'no-clean' solder, but it's 
really not very nice to work with.

Seb