What you haven't provided us with is what type of assembly process you
have. Do you clean after soldering or is a no clean facility? Do you also
conformal coat the edges of the cards?
If you do clean your assemblies (especially before conformal coating), then
perhaps all contamination is getting washed off of the assemblies and there
may not be any issue.
If you do not clean your assemblies after allowing your operators to handle
them without protection from contamination, then I would be surprised if
the assemblies can pass an ionics test consistently.
Our policy is latex fingercots or esd-approved vinyl gloves because we have
a high reliability based no clean soldering process and we find excessive
contamination through ionics testing when improper handling (without
protection) occurs.
When installing fingercots, they roll them on and do not contaminate the
clean surface on the outside. In addition, they discard them at every
break/lunch/dinner.
One day of an operator with silicone contamination on his/her fingertips
will ruin one's whole week in a conformal coating operation.
However, be careful in approving the fingercots and gloves which are touted
to be static protective, as they must also be clean room qualified as well.
Test, test, and test them some more.
Phil
At 11:02 AM 11/24/99 -0500, Kane, Joseph wrote:
>Technetters:
>
>Our new Space customer may be pushing us to use static-protective gloves or
>finger cots for soldering and assembly operations. We prefer to continue
>our current practice, having operators exercise due care and handle product
>by the edges only, and use gloves only for hot things or when using some
>chemicals. This has worked well for all of our high-rel product, including
>flight controls and aircraft engine controls. When we do 10-day humidity on
>conformal coated assemblies, we occasionally see mealing patterns in the
>shape of fingerprints, but not very often.
>
>Some of the problems we see with the alternatives, in approximate order of
>importance:
>
>1. Gloves and finger cots compromise dexterity and tactile sensitivity.
>Maybe not much, but some. Productivity suffers, defects go up, and maybe
>some things get dropped that normally wouldn't.
>2. Contaminants deposit on gloves or finger cots, obviating any benefit.
>By contrast, when operators get flux or adhesives on their bare fingers,
>they can feel it, and they go wash their hands, or at least wipe them on
>something.
>3. Finger oils still get on gloves or finger cots. You have to handle them
>with bare hands to get them on, and then everyone's nose needs a scratch
>once in a while.
>4. Operators hate them because they are cumbersome and uncomfortable. Some
>would say tough luck, and if there were good reasons we would force the
>issue, but as it is this looks like another compliance issue/audit trap that
>we don't really need.
>5. Over time, some people develop sensitivity to latex, maybe even nitrile.
>6. They cost money.
>
>Like bunny suits or respirators, I don't know why anyone would use these
>things unless there was a good reason. Anyone out there have any
>experience, good or bad?
>
>
>Joe Kane
>Lockheed Martin Control Systems
>
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