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How To Setup an ESD Workstation by ly5C2g8y


									                             How To Setup an ESD Workstation
                      Written By: Gene Felder of Desco Industries, Inc.

According to ANSI/ESD S20.20 section 8.3 “An EPA [ESD protected area] shall be established
wherever ESDS [ESD Sensitive] products are handled. However, there are many different ways
to establish ESD controls within an EPA. Table 3 lists some optional ESD control items which can
be used to control static electricity. For those ESD control items that are selected for use in the
ESD Control Program, the required limits and test methods for that item becomes mandatory.”

Here are the EPA ESD control items that can be selected:

There are ESD protective workbenches, and selecting one would be best practice. However,
most companies with use a regular workbench. Materials used can vary, but it is best to use a
workbench that is constructed of metal and wood, and not one containing large portions of high
charging insulative plastic.

A basic ESD control rule is to ground all conductors including people at the ESD workstation.
Grounding works great and will reliably remove ElectroStatic Charges to ground. The building’s
Equipment Grounding Conductor or AC electrical (third wire, green) will normally be the ground of
choice. Electrical outlets need to be checked to verify the correct wiring of hot, neutral, and

Common Point Ground
Each workstation should have one common point ground. Per ESD Handbook ESD TR20.20
section 5.1.3 Basic Grounding Requirements “The first step in ensuring that everything in an EPA
(ESD Protected Area) is at the same electrical potential is to ground all conductive components of
the work area (worksurfaces, people, equipment, etc.) to the same electrical ground point. This
point is called the common point ground. The next step in completing the ground circuit is to
connect the common point ground to the equipment ground (third wire, green).” Most locate the
common point ground at the side edge of the workbench or towards the back of the benchtop.

Wrist Strap System
Most workers, required for sitting workers, will be grounded via a Wrist Strap System. The wrist
strap needs to be selected and there needs to be an adequate number of ground points available.
Even if typically the workstation is for only one worker, more than one ground point should be
available to ground an addition worker, supervisor, or other ESD control element.

Worksurface Mat
Most workstations will use pliable ESD matting to cover the bench and be the ESD worksurface
on which to handle ESD sensitive (ESDS) items. The mat needs to be grounded and best
practice is to use metal grounding hardware snaps and ground cords connecting the worksurface
mat to the common point ground. The entire benchtop should be covered by the ESD mat.

Matting can be conductive or dissipative. Per ANSI/ESD S20.20 the required limit is less than 1 x
10E9 ohms and ANSI/ESD S4.1, the worksurface standard, recommends a low limit of 1 x 10E6
ohms. Per S4.1 “These guidelines represent a range of resistance that has generally been proven
to provide protection in the manufacturing environment.” This dissipative matting has the ESD
control benefit of more slowly removing electrostatic charges to ground when charged ESDS
make contact with the mat’s worksurface.

If the use of continuous or constant monitors is a possibility, selected mating should have a more
conductive layer such as Statfree T2™ dual layer rubber or Statfree Z2™ three layer vinyl matting
which has a conductive mesh middle layer.
It is not required to have ESD flooring, but it could be selected to be low charging and/or a means
to ground mobile equipment. Per S20.20, the required limit for Flooring is less than 1 x 10E9
ohms. For a standalone ESD workstation, a floor mat can be used with a ground cord connected
to the workstation’s common point ground. We recommend conductive floor matting less than 1 x
10E6 ohms to be able to meet the Flooring/Footwear required limit of less than 3.5 x 10E7 ohms
(see below).

Instead of a wrist strap, a standing or mobile worker can be grounded using a Flooring/Footwear
System. So ESD shoes or foot grounders can be selected. This means of personnel grounding
requires both ESD flooring and ESD footwear. The ESD footwear is to be on both feet. Unless
body voltage testing has been completed, the required limit per Compliance Verification ESD
TR53 is of less than 3.5 x 10E7 ohms. Best practice is to use sole grounders or full coverage
grounders and not heel grounders.

ESD TR53 defines a wrist strap or ESD footwear test (while worn by the worker) that can quickly
be tested using a tester.

A bench-top ionizer or overhead ionizer can be selected to neutralize ElectroStatic charges at the
workstation. This is the only ESD control method available to neutralize ElectroStatic charges on
essential insulators or isolated conductors that may be at the workstation. The required limit per
S20.20 is less than +/- 50 volts offset voltage (balance). In addition, the Discharge Times should
be measured, both the time necessary to reduce +1,000 volts to +100 volts, and the time
necessary to reduce -1,000 volts to -100 volts. The user gets to determine what the required limit
is for Discharge Times. However, per ESD TR53 “measurements should be made at the location
where ESD sensitive items are to be ionized.” So the Discharge Time tests should occur the
furthest away from the ionizer where ESDS are handled.

The most accurate tool to use for testing ionizers is a Charged Plate Monitor. Alternatively, a
portable battery operated Ionization Test Kit can be used.

Packaging and material handling containers at the ESD workstation should be low charging and
have resistance (conductive or dissipative) so ElectroStatic charges can be removed to ground.
Shielding bags are also used additionally having the ESD control property of discharge shielding.

Per ESD Handbook ESD TR20.20 section 2.4 “It should be understood that any object, item,
material or person could be a source of static electricity in the work environment. Removal of
unnecessary nonconductors, replacing nonconductive materials with dissipative or conductive
materials and grounding all conductors are the principle methods of controlling static electricity in
the workplace, regardless of the activity.” So all insulators should be removed or replaced by
using ESD protective version of the item. This could include:
     Continuous Monitors
     ESD seating
     ESD carts
     ESD smocks
     ESD gloves
     Conductive foam and shunt bars
     ESD tape
     ESD cleaners and topical antistat
     Dissipative bottles and cups
     Dissipative binders
       Dissipative document and badge holders
       ESD hand lotion

The ESD workstation should be clearly identified as such. Per ANSI/ESDS20.20 section 8.3
“Caution signs indicating the existence of the EPA shall be posted and clearly visible to personnel
prior to entry to the EPA.”

Compliance Verification
When setting up an ESD workstation, the EPA ESD control items should be measured to verify
that they meet the required limit as specified in ANSI/ESD S20.20. Compliance Verification
testing per ESD TR53 should occur on a regular basis. Per S20.20 section 7.3 “Process
monitoring (measurements) shall be conducted in accordance with a Compliance Verification
Plan .... Compliance verification records shall be established and maintained to provide evidence
of conformity to the technical requirements. The test equipment selected shall be capable of
making the measurements defined in the Compliance Verification Plan.”

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