There are some key points to make.
- Your hands are washed 6-10 times a day and would overall be cleaner than any glove.
- Proper handling is paramount where you handle the boards from the board edges. Most of the time before and after SMT reflow the boards are still in panels with break-away rails so the boards are never touched.
- The biggest issue I've had is with OSP boards in the pre-wave prep. The person applying kapton tape masking must use a wooden or plastic stick or finger cots to avoid contact with the board as they press the tape down to make the required seal.
On Enig and HASL boards we insist that only a designated person applies the tape and that person washes their hands everytime they come back from break, before they start tape masking.
After reflow, AOI and wave or selective solder the boards are depaneled.
However the majority of the soldering has been completed and the boards are washed so the small chance of someone contaminating a pad or annular ring, reducing wetting is mute.
With gloves you can't handle nor load small parts pre-wave and the gloves are going to pick up everything on the bottom of ESD trays, racks, benches, ESD parts bins etc. The cost to benefit ratio, including assembly efficiency is just not there.
- The customer and integrator is not going to be wearing gloves when they handle boards.
- A finger print on the epoxy mask is not a reliability issue and has never been a defect in the cleanliness standard in IPC-A-610.
Proper board handling, process control and training is far more effective than just spending lots of money on gloves which would have collect every contaminate and slow down the assembly process.
John Goulet Process Engineer
----- Original Message -----
From: "Mike Fenner" <[log in to unmask]>
To: [log in to unmask]
Sent: Thursday, March 5, 2009 4:31:41 AM GMT -05:00 US/Canada Eastern
Subject: Re: [TN] Gloved Hands / Fingerprints / Failure Articles
Well.... Dirty money and that.
Coins are usually thought of as being dirty having been through lots of
hands, but in those made from copper alloys the bug count is actually low.
Not so with the folding stuff!
Regards
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Dixon
Sent: Wednesday, March 04, 2009 3:46 PM
To: [log in to unmask]
Subject: Re: [TN] Gloved Hands / Fingerprints / Failure Articles
I totally agree with Doug. I mentioned this several years ago on this
forum.....and feel it is safe to repeat now!
I went to a fast food place and the guy running the cash register was
wearing gloves... How nice since that money is really filthy... Then
he walked over to the kitchen and prepared my food while wearing those
same gloves! I lost my appetite!
Regards,
Dave
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, March 04, 2009 8:50 AM
To: [log in to unmask]
Subject: Re: Gloved Hands / Fingerprints / Failure Articles
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
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