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From [log in to unmask] Wed Jan 31 11: |
23:48 1996 |
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RON Rawlyk ,SED Systems Inc.
asked about white spots an poor adhesion of
solder mask after flux removal using a saponifier.
I suggest the following:
Saponification is a pretty fierce process -its basically similar to that used
for
caustic stripping paint from old furniture, cleaning domestic ovens).
Saponifiers have infinitely more potential for damage than a resin flux
So everything has to be right for it to work OK. However saponification is the
original
non solvent rosin flux removing process
- it has been in use for 20-30 years for pcbs so should be able to get it
working.
Try the obvious things first
Ensure resist is cured, the soldering iron idea is quite a good one,
as a test, but you run the risk of degrading the resist if you leave the iron on
too long.
I would prefer an oven bake say 1 hour at 100-150C on boards as received,
this then gives you a usable fix till you can get a solution.
Part cured resist will come off easily in saponifier see above
Make sure that you are not looking at water hardness spots, that are being dried
into defects in resist.
ie make sure your DI water is DI, softener working OK etc.
Maybe you could interupt you cycle and hand rinse some trial boards in known
good DI
as a check
Do you really need those process temperatures? Seems pretty hot to me,
Longer term, do you really need this process? The only reason for saponification
is to
convert your solvent soluble rosin into something you can wash away with water.
Why not start with a water washable flux?and before you say corrosion
refer to top of this message.....
Mike Fenner
BSP, UK.
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