Hi, Bob.
I assume you mean a factory, not just the floor itself.
There are at least 5 components to a good ESD control program. In order
for the program to work, all 5 cylinders must be firing. The 5 main
control factors are:
1. A good conductive ESD floor. Even a bare concrete floor with the
proper floor treatments can effectively provide a non-tribocharging
surface and drain potential ESD charges to the building ground. But if
you are serious about this then get a good ESD tile floor installed.
Note! The conductive epoxy/tile flooring can be disastrous if not
properly applied, even by qualified installers. If you choose this type
of flooring make sure that the company that you buy the tile from
approves the installer. Should the installer put the epoxy down
incorrectly, the floor will not meet the measurement specs, and the tile
company will not warrant the installation as a result.
Temporary ESD floors are available with all of the ESD performance and
durability and none of the permanency issues. These can be installed in
a working factory a section at a time to avoid impacting production,
unlike epoxy/tile in which the entire area must be cleared of all
equipment and the whole floor done at once. See an example of this
removable conductive grid and the ESD tiles that go with them at
http://www.tekstilconcepts.com/products/adhesives/adh-electronic.shtml.
In past lives I have used their flooring for two large EMS corporations
after I reviewed several other installations at major OEMs. I fully
checked this out with these people and they were very happy with the
performance and the appearance of the floors, and so was I after I had
the Sigaway/Tekstil installed. With this system the tiles can be removed
from the conductive Sigaway backing and re-used with a new application
of the backing should you need to move the flooring from one area (or
building) to another.
2. The assembly protection system. This would include proper grounding
of all of the benches and shelves, with no daisychained workstations or
shelving units (each connected to ground separately). There are
sometimes situations where it is sometimes impractical to do this, but
individual grounding should be the target. Daisychains can be broken at
a single point, causing an entire line or area to become ungrounded.
Assemblies should be kept in Faraday boxes or bags if they are not being
worked on. Ionizers should be considered if class 0 assemblies are going
to be worked on. This includes a Machine Model ESD analysis of each
machine the assembly will come in contact with.
Note! Most ESD damage is from the Machine Model, not the Human Body
model.
3. Environmental control, monitoring and controlling the humidity
between 20% and 60% RH (ideally) and with warning steps that kick in
automatically should the humidity go above or below those levels.
4. Properly grounded operators, including ESD-safe shoes or heel straps,
proper smocks with either ESD elastic wrist cuffs or smock ground
connections to pass the charges accumulated on the smock to the
operator's skin or to electrical ground, where it is dissipated through
the ESD footwear or wrist strap or ground connection. There should be
either a daily check of the footwear and wrist straps to verify they are
working, or use a constant-monitor ESD system.
5. An ESD-Training program with a certified instructor, whether it is to
EOS/ESD STD 20.20-1999 or MIL-STD-1686C or other standard. Training and
certification is required, along with a good auditing program to show
compliance. The quality records must be kept up.
Get a copy of either ESD standard and read it through. Note that there
is no actual requirement in 20.20, but you need to perform an assessment
to determine just what your ESD program should include and you should
have a written justification for the level of controls you feel you
require. Please note that if you have all 5 components fully
functioning, you will have less to worry about should any one of the
components fall out. For example, if an operator fails to plug in their
wrist strap or the cord opens up, the humidity controls, the conductive
footwear, the flesh-grounded smock, the conductive floor, and the
grounded benchtop/matting/fixtures are all working together to continue
to protect that assembly. If you delete any of the systems, you
incrementally increase your risk of ESD damage. As a minimum, I would
ground the benches with dissipative mats, ground the shelves if there is
any chance that unprotected ESD assemblies will be laid on them outside
of their Faraday containers, and require the operators to wear wrist
straps whenever handling unprotected assemblies. I would also require
all equipment and fixtures to be grounded. This makes the flooring and
humidity controls optional, but you have little or no comprehensive
protection.
ESD compliant floors covering the entire production area are not always
necessary if good controls can be put in place to protect the hardware
while moving from point A to point B. If that is the case then smaller
ESD floor mats can be put down rather than tile.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Wilson
Sent: Friday, September 15, 2006 12:06 PM
To: [log in to unmask]
Subject: [TN] ESD protection
Hey everyone,
Happy Friday!
Can anyone point me to the best way to set up a shop floor for ESD
protection?
Thanks a bunch.
Regards,
Bob Wilson
Electro-Mechanical Designer, CID
SpectraSensors, Inc.
972 N. Amelia Ave.
San Dimas, CA 91773
800-619-2861 x239
www.spectrasensors.com
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