G Electrostatic Discharge (Esd) Practices; Overview; Handling Esd Sensitive Devices - Novatel OEM6 Series User Manual

Appendix G
G.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.
G.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.
• Do not allow chargeable plastics, such as binders, within 0.6 m of unshielded PCBs.
• Do not allow a PCB to come within 0.3 m of a computer monitor.
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Electrostatic Discharge (ESD) Practices
OEM6 Family Installation and Operation User Manual Rev 7