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Date: | Fri, 20 Jul 2007 09:50:40 -0400 |
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July 20, 2007
We have an OEM that has an ESD control program in place per the subject
specification invoked via J-STD-001. However, my position is that he does
not comply with the requirements since during his conformal coating hand
spray process, he places the PWAs ontop of cardboard then sprays them with
coating (no ionizer machine is used in the coating area). Additionally,
sometimes ESD sensitive assemblies are placed on top of cardboard or wooden
blocks during the assembly or inspection process. In all cases when wood or
cardboard is used, the wood and cardboard rests ontop of a properly grounded
ESD mat, and the operator is grounded via a properly connected wrist strap.
I maintain that this practice violates the subject specification since wood
and cardboard are insulating materials which are not to be used at the
workstations, and if one took a surface insulation resistance measurement
across the wood or cardboard surface, one would obviously not meet the value
specified for a properly grounded mat.
I would appreciate any comment on the above, and whether other folks use
wood or cardboard upon which ESD assemblies rest. How do other folks
support assemblies during conformal coating or assembly/inspection if wood
or cardboard is not used?
If the operator is properly grounded via a wrist strap, would any static
charge that may exist on the cardboard or wood surface dissipate through the
wrist strap without damage to the product? I suspect not otherwise there
would be no need to require that the grounded mats be used.
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