Bev
This reminds me of a case I was consulting on. I saw they were adding trimmer pots by
hand after cleaning. Why? Because the purchasing manager was buying non-hermetic
components which were about 10 cents cheaper than the hermetic version. How much did it
cost to add them afterwards? About 90 cents. Net loss 80 cents per component or $6.40
per board, 200 boards per day = $1,280, all because the purchasing manager thought he
was doing his job well.
The cure for this is called concurrent engineering where no-one in the whole team has
the right to dictate anything to the rest, without solid justification. The question to
ask is why do the PPS capacitors have to be used. Assuming there is a good reason (and
I cannot think of one, as the PF of PPS capacitors is not brilliant), then is there a
hermetic version available? If not, why do they not like water? Now, here's the rub. If
they don't like water, it is because their guts are open to water. If they are open to
water, then they are open to any other solvent. Ask the designers whether they would be
happy to have contaminated solvent resident in their dearly beloved caps. Then ask them
whether they realise how much it will cost to install and qualify a new cleaning line
just because of these stupid components which are actually more expensive than other
types. AND are you sure all the other components will stand up to the organic solvent?
No polystyrene, no polycarbonate, no PVC, no PMMA, no soldermasks of some types?
And what about the cost of changing the paste and qualifying it to optimise cleaning by
a different method?
All in all, you are talking big bucks to do such a conversion for a single component
type.
Now, let's talk vapour phase. I recently visited a client who was using one of these
new toxic and ozone-depleting nPB-based solvents (God forbid!) in a very expensive
installation. He was not cleaning well under large (8 x 9 mm) ceramic caps but his
stand-off was very small (one layer of hybrid conductive paste). Flux removal was
effective for about 2 mm along the open edges. If he added ultrasonics, he may add
another mm or so, but I doubt if he could guarantee complete removal, but I don't know
of any other method that would do better.
Sorry to be such a Cassandra, Bev, but someone has put you in a lose-lose situation.
Really, the only easy way out is to go "no-clean" for these boards, IMHO. If this is
not acceptable, then something really has to give and I seriously suggest that it be
the caps, as being the only economical solution.
Brian
Bev Christian wrote:
> Brian,
>
> I think my reply to Phil probably answers your question, but I will
> re-iterate. I have nothing against vapour phase and
> aqueous cleaners, my squirrelly little parts are the ones that don't like
> water. As far as vapour degreasers, will they really do the job for modern,
> low standoff components? I seem to recall Doug Pauls saying cleaning under
> these at the best of times was difficult, so I thought that a more
> physically aggressive system would be needed. Am I wrong? This old
> no-clean goat stands ready to be educated.
>
> regards,
> Bev
>
> -----Original Message-----
> From: Brian Ellis [mailto:[log in to unmask]]
> Sent: Friday, July 28, 2000 1:50 PM
> To: TechNet E-Mail Forum.; Bev Christian
> Subject: Re: [TN] 100% Non-Aqueous Cleaners
>
> Bev
>
> What exactly are you trying to do? I don't really understand your question
> as very few
> non-vapour degreasing/non-aqueous systems will give very good results, IMHO
> (from
> experience). Are you willing to have highly flammable solvents or
> combustible ones: if
> the latter, how are you going to dry? What have you got against vapour phase
> and
> aqueous cleaners, which have both proved, in certain cases, to be acceptable
> or even
> good?
>
> In other words, are you not making a stick for your own back?
>
> Brian
>
> Bev Christian wrote:
>
> > Technetters,
> > Any recommendations about self-contained, batch, non-aqueous systems? I
> am
> > not referring to vapour degreaser types. I am looking for something with
> an
> > active cleaning cycle. Comments about different solvents would also be
> > appreciated. Dealers/manufacturers may write to me directly to avoid
> > getting flamed. Thanks.
> >
> > Bev Christian
> > Director of Manufacturing
> > XLTEK
> > 800-387-7516, ext 295
> >
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