Excellent, practical, pragmatic advice. Worth its weight in Mountain
Dew.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Wednesday, March 04, 2009 8:44 AM
To: [log in to unmask]
Subject: Re: [TN] Gloved Hands / Fingerprints / Failure Articles
Kevin,
I will throw in my two cents worth. We do not wear gloves in our
facilities for most of the manufacturing process. They do in the clean
rooms and they do after final wash prior to conformal coat. The rest of
the time it is, in my opinion, a waste of time and money. Kind of an
odd statement coming from me, but here is why I think so.
Gloves are there to prevent finger salts and oils from getting on the
assembly, where they would be a contamination risk. Our cleaning
processes are such that the last cleaning step is a mild one designed to
remove such salts and oils. The heavier residues have already been
removed in previous process steps. So, gloves are not really needed.
Here is why I think it is a waste of money to have gloves on anywhere
earlier in the process. The assumption that gloves keep your assemblies
clean is only true while the gloves themselves are clean. Run your
gloved hands through your hair. New gloves. Touch a little of that
uncured adhesive. New gloves. Get a little flux from hand soldering on
the gloves. New gloves. You think that the operators are going to
change gloves that often? No. Think the manager for that area is going
to willingly pay for the truckloads of new gloves. Hell no. In some of
our areas, the operators that apply silicone RTV adhesive to the boards
wear gloves because that RTV is hard to get off your hands. Think they
change them often? Nope. When the boards get to conformal coating,
there are lots of dewet areas that mysteriously resemble fingerprint
sized areas, but without the convenient identifying fingerprints. Even
though we stress to our operators to handle boards by the edges only, it
is sometimes just not practical to do so. Then again, since we have
that final clean prior to coating, it is not as critical.
Now, if you are a true no-clean facility, that is another issue. If you
go the route of gloves, I would recommend you stay away from finger cots
and plastic gloves. They are uncomfortable and when you make the
operators uncomfortable, bad things happen. I would highly recommend
the use of HyFlex gloves, which you can get from Techni-Tool. These are
cotton gloves with heavier rubberized palms and fingers, but the back
sides of the fingers and back side of the hand are open cotton, allowing
the gloves to breathe. Very comfortable, good tactical feel to them and
the surface is robust enough that you can clean off residues with mild
alcohol so they last for a long time. They cost a little more, but they
are worth the investment considering their cleanability and how long
they last.
Doug Pauls
Rockwell Collins
Kevin Glidden <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
03/04/2009 07:26 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Kevin Glidden <[log in to unmask]>
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Subject
[TN] Gloved Hands / Fingerprints / Failure Articles
Hello everyone,
We are in the midst of a proposal from myself and manufacturing
engineering
to require use of gloves or finger cots throughout our PCB assembly
process.
We had considered that it really would only be required after final
cleaning, but for uniformity would require it all steps including
population. We have of course met with a real resistance, particularly
from
the final assemblers who are stating it doesn't matter once the
conformal
coat is on. I can see at least some logic in that, and admittedly a
large
portion of our argument is aesthetics (we don't want fingerprints on the
boards even after coating), but it would be really nice to have some
sort
of
scare tactic, like an article or something that related a PCB failure to
fingerprints or handling contamination. Anyone have such a thing?
Thanks!
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