Brian,
Thank you for one of your usual well thought out replies. Some of the
arguments I have already used. Some are new. Perhaps they will listen to
an "outsider", when I pass this along. One question: what does PF stand for
(picofarads)?
regards,
Bev
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Saturday, July 29, 2000 2:21 AM
To: TechNet E-Mail Forum.; Bev Christian
Subject: Re: [TN] 100% Non-Aqueous Cleaners
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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