OEM6 Family Installation and Operation User Manual Rev 12
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Appendix J
Electrostatic Discharge (ESD) Practices
J.1
Overview
Static electricity is electrical charge stored in an electromagnetic field or on an insulating body. This charge
can flow as soon as a low impedance path to ground is established. Static sensitive units can be permanently
damaged by static discharge potentials of as little as 40 volts. Charges carried by the human body, which can
be thousands of times higher than this 40 V threshold, can accumulate through as simple a mechanism as
walking across non-conducting floor coverings such as carpet or tile. These charges may be stored on
clothing, especially when the ambient air is dry, through friction between the body and/or various clothing
layers. Synthetic materials accumulate higher charges than natural fibers. Electrostatic voltage levels on
insulators may be very high, in the order of thousands of volts.
Various electrical and electronic components are vulnerable to ESD. These include discrete components,
hybrid devices, Integrated Circuits (ICs) and Printed Circuit Boards (PCBs) assembled with these devices.
J.2
Handling ESD Sensitive Devices
ESD sensitive devices must only be handled in static controlled locations. Some recommendations for such
handling practices follow:
•
Handling areas must be equipped with a grounded table, floor mats and wrist strap.
•
A relative humidity level must be maintained between 20% and 80% non-condensing.
•
No ESD sensitive board or component should be removed from its protective package, except in a
static controlled location.
•
A static controlled environment and correct static control procedures are required at both repair
stations and maintenance areas.
•
ESD sensitive devices must be handled only after personnel have grounded themselves via wrist
straps and mats.
•
Boards or components should never come in contact with clothing, because normal grounding
cannot dissipate static charges on fabrics.
•
A circuit board must be placed into a static shielding bag or clamshell before being removed from the
work location and must remain in the protective enclosure until it arrives at a static controlled repair/
test center.
•
Circuit boards must not be changed or moved needlessly. Handles may be provided on circuit boards
for use in their removal and replacement; care should be taken to avoid contact with the connectors
and components.
•
On-site repair of ESD sensitive equipment should not be undertaken except to restore service in an
emergency where spare boards are not available. Under these circumstances repair station
techniques must be observed. Under normal circumstances a faulty or suspect circuit board must be
sent to a repair center having complete facilities or to the manufacturer for exchange or repair.
•
Where protective measures have not been installed, a suitable alternative would be the use of a
Portable Field Service Grounding Kit (for example, 3M Kit #8501 or #8507). This consists of a
portable mat and wrist strap which must be attached to a suitable ground.
•
A circuit board in a static shielding bag or clamshell may be shipped or stored in a cardboard carton,
but the carton must not enter a static controlled area such as a grounded or dissipative bench top or
repair zone. Do not place anything else inside the bag (for example, repair tags).
•
Treat all PCBs and components as ESD sensitive. Assume that you will damage the PCB or
component if you are not ESD conscious.
•
Do not use torn or punctured static-shielding bags. A wire tag protruding through the bag could act as
a "lightning rod", funneling the entire charge into the components inside the bag.
