Howard
I suspect it may have a very negative effect on reliability, depending
on individual conditions. In a former life, when my now-defunct company
(I'm now "retired") made the Microcontaminometer, we tested hundreds of
components, taken at random, just to see how the instrument performed.
The results were enough to make one's hair stand on end. OK, some were
clean, but the majority were higher than would be acceptable for a bare
board and some went up to 20 times higher. I cannot believe that these
levels of contamination cannot have some impact on reliability,
especially under "no-clean" conditions. If you look at the chapter on
contamination on components in my book, you will see a photo of a DIL
where the leads are pitted by the corrosion engendered by contamination.
Apart from this risk, who knows what happens to the flux chemistry by
residues on the components? It certainly will never be optimal and one
of two (or both) things are possible: a) the quality of soldering may
deteriorate or b) the residues may be far more dangerous. Reliability?
Never!
Incidentally, even if cleaning is carried out, there can never be a
guarantee that it will remove the residual contaminants, when you cannot
even tell what they are (e.g., modified residues from gold plating may
be insoluble in water after reacting with an acid flux activator).
What to do about it? Small or medium companies do not have enough clout
with component manufacturers to force them to supply clean components.
It is up to the Siemens, Philips, IBM and other large companies to force
the issue. However, the smallest company can periodically test
components from competitive manufacturers and force purchasing to choose
the best. This should all be part of Concurrent Engineering. Purchasing
managers should be forced to realise that the cheapest is often the most
expensive. I've often cited a case where a purchasing manager bought
some cermet trimmers at a savings of c. 5 c, but they cost manufacturing
nearly a dollar in post mounting/hand soldering, because they could not
be cleaned. Very false economy. I believe that the next issue of PC
Design mag will have an article along these lines.
Brian
Howard Watson wrote:
>
> Brian,
>
> I totally agree. Component contamination is a large contributor to
> defects at our facility, and I do not know how it affects reliability.
> I suspect that purchasing gets the best deal on components, which
> ends up costing us later. We argue this point often, but honestly I
> don't know what else to do about it, with our limited resources. Any
> suggestions? Thanks for the feedback.
>
> Howard Watson
>
> Brian Ellis <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]> To:
> [log in to unmask]
> 02/22/01 12:38 AM cc:
> Please respond to "TechNet E-Mail Subject: Re:
> Forum."; Please respond to Brian Ellis [TN] Washing of no-clean
>
> Howard
>
> And what about the contamination on the components? In my experience,
> this is often, by far, worse than that on the boards.
>
> Brian
>
> Howard Watson wrote:
> >
> > Graham,
> >
> > We don't demonstrate our end product reliability. What we do, per
> the
> > consultants advice, is to:
> >
> > 1. Ensure that the no-clean flux we use passes Bellcore
> > specifications.
> > 2. Use the Ionograph and electromigration tests to determine bare
> > board cleanliness, and work with our suppliers to ensure the
> > boards are clean (to our specs).
> > 3. Use Certificates of Compliance as the conforming document for
> > solder, solder paste, and flux. Occasionally challenge the C
> of
> > C's.
> > 4. Monitor and control our processes, to ensure that variation is
> > reduced.
> >
> > Basically, the process controls we have in place, I am told,
> will
> > satisfy our customer (so far, so good). If our customer
> requires
> > demonstration of end product reliability, then we will proceed
> > down that path.
> >
> > Howard Watson
> >
> > "Graham Naisbitt"
> > <[log in to unmask]> To:
> "TechNet
> > E-Mail Forum."
> > 02/21/01 09:48 AM <[log in to unmask]>,
> >
> <[log in to unmask]>
> > cc:
> > Subject:
> RE:
> > [TN] Washing of no-clean
> >
> > Howard,
> >
> > It would be interesting to understand how you demonstrate your
> > end product reliability.
> >
> >
> > Regards, Graham Naisbitt
> >
> > [log in to unmask]
> > www.concoat.co.uk
> >
> > Concoat Limited
> > Alasan House, Albany Park
> > CAMBERLEY GU16 7PH UK
> > Phone: +44 (0)1276 691100
> > Fax: +44 (0)1276 691227
> > Mobile: +44 (0)79 6858 2121
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]]On Behalf Of Howard
> Watson
> > Sent: Tuesday, February 20, 2001 08:27
> > To: [log in to unmask]
> > Subject: Re: [TN] Washing of no-clean
> >
> > You guys are right on target here. We have a major customer
> who
> > is world leader in the heavy vehicle industry, and they were
> (and
> > I think still are) very skeptical of our no-clean process (we
> > also use Multicore paste). We have taken great strides to
> > convince the customer that the no-clean process meets all
> > industry specifications, and we have set up process controls to
> > prove it. We hired a very high ranking consultant to set us on
> > the right track with our customer. The consultant strongly
> > advises against cleaning the "no-clean" flux. The alternative,
> > to do the job correctly, would have been a $250,000 investment
> > for a cleaning system.
> >
> > Howard Watson
> >
> > Lou Hart <[log in to unmask]>
> > Sent by: TechNet <[log in to unmask]> To:
> > [log in to unmask]
> > 02/20/01 09:09 AM cc:
> > Please respond to "TechNet E-Mail Subject:
> Re:
> > Forum."; Please respond to Lou Hart [TN] Washing of
> no-clean
> >
> > I was hoping someone would say what Brian has here, on behalf
> of
> > manufacturers. If you want something more than conformance to
> > our
> > standard, 610 class 2 product, tell us you want it up front and
> > be prepared
> > to pay for it. This business is not a philanthropic
> enterprise.
> > It may be
> > advisable to give some free advice in this area, however, by
> > telling the
> > customer he may be wasting his money.
> > Lou Hart
> > -----Original Message-----
> > From: Brian Ellis [SMTP:[log in to unmask]]
> > Sent: Tuesday, February 20, 2001 9:21 AM
> > To: [log in to unmask]
> > Subject: Re: [TN] Washing of no-clean
> >
> > Ioan
> >
> > Well, if they want it clean, they will have to pay for it,
> > n'est-ce-pas?
> > If they don't want to pay, the corollary is that they should
> put
> > up with
> > the minimal residues from a good low-solids, "no-clean"
> > flux/paste.
> >
> > If you buy a car and want to enhance its appearance with
> > "speed-stripes"
> > or a spoiler, do you think your supplier will do it for free?
> >
> > Brian
> >
> > "Tempea, Ioan" wrote:
> > >
> > > Sorry for the missing details.
> > >
> > > The product is regular office equipment, so not a demanding
> > one. The
> > request
> > > for cleanliness is purely aesthetical.
> > >
> > > By the way, no premium involved. They want it clean and
> that's
> > it.
> > >
> > > Regards,
> > > Ioan
> > >
> > > > -----Original Message-----
> > > > From: Brian Ellis [SMTP:[log in to unmask]]
> > > > Sent: Tuesday, February 20, 2001 2:31 AM
> > > > To: TechNet E-Mail Forum.; Tempea, Ioan
> > > > Subject: Re: [TN] Washing of no-clean
> > > >
> > > > Ioan
> > > >
> > > > Whoa! Be careful here. If your clients are wanting
> cleaning,
> > there is a
> > > > reason why they are willing to pay a premium. What is it?
> If
> > it is
> > > > purely for aesthetics, then no great deal. If it is for
> > technical
> > > > reasons, what degree of cleanliness is required? What is
> the
> > end-use
> > > > application? If it is critical, then you must do the job
> > properly and
> > it
> > > > would be unlikely a bench-top system would give adequate
> > results, at
> > > > least without multiple stages and excellent process
> control.
> > > >
> > > > Please let us know more.
> > > >
> > > > Brian
> > > >
> > > > "Tempea, Ioan" wrote:
> > > > >
> > > > > Hi technos,
> > > > >
> > > > > I need your expertise again.
> > > > >
> > > > > We are on no-clean and newer clients ask us to clean the
> > residue. I
> > need
> > > > to
> > > > > know if any equipment exists to do this job, except for
> the
> > big
> > washers.
> > > > I'm
> > > > > thinking of a small (table top) tank, followed by some
> > drying thing.
> > > > > Then, is the simple dipping of the board enough to wash
> > away the
> > > > residue, or
> > > > > some agitating action is needed?
> > > > >
> > > > > We are on X33 flux from Multicore and I think I can get
> > from them the
> > > > right
> > > > > substance that would do the cleaning. However, if you
> > happen to have
> > > > > suggestions...
> > > > >
> > > > > Thank you,
> > > > > Ioan
> > > > >
> > > > >
> > > >
> >
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