[sdiy] Board Cleaning, Was: Super S/H doc

[Neil Johnson]

Sorry if the following offends, but I think after years of seeing
these kinds of threads regularly pop up, I need to say it:

STOP WASHING YOUR BOARDS!!!

Seriously, most folks here don't understand what they're doing, and
more than likely doing far more harm than good.  Any washing process
is destructive at some level, and unless you have a washing system
that completely and safely removes all contaminants all you are really
doing is spreading the shit all over your boards rather than leaving
it alone.

And even if you DID clean your boards properly, there are plenty of
components that you can't wash and so must be fitted after washing
(pots, switches, wires, some capacitors, etc) leaving flux residues on
the board.

There are specific cases where cleanliness is important.  For example,
Ian's S&H, but in this case the alcohol is to remove surface
contaminants such as finger grease, which will otherwise increase
surface leakage currents unless removed.

The other thing I still don't "get" - water soluble flux in a hobby
environment.  It is a highly-corrosive acidic flux.  Fine.  And you
read the flux datasheet and they go into great detail about how to
clean boards.  And that's fine for a production environment where the
soldered boards are then put into a board cleaning machine, operated
by folks who know what they are doing, regularly checking the cleaning
process and following the manufacturer's instructions.  For example, a
popular brand here in the UK is Hydro-X flux, and the datasheet has
the following to say about cleaning:

--

CLEANING
It is essential that the residues from soldering with Multicore
Hydro-X cored solder wires be removed as soon as possible after
soldering.  The residues from Multicore Hydro-X cored solder wires may
be readily cleaned in conventional equipment using water. It is
important that the cleanliness of boards and components is thoroughly
checked after soldering and cleaning. The usual procedure is to
continuously check the conductivity of the final rinse water as a
measure of ionic contamination. Samples of cleaned boards should be
subjected to a laboratory corrosion test, insulation
resistance test, or ionic contamination assessment.

--

Simply rinsing a board under a running tap might appear to be ok, but
how do you know you haven't left any drops of contaminated wash water
in little corners or traps?  How do you check that you have correctly
rinsed the board?  Do you check the conductivity of the rinse water?
Or do you simply hope?

In summary: use no-clean flux, don't clean unless one of the very rare
cases where it is necessary.  Enjoy life.

Neil