Table of Contents
Advertisement
A
ANTI-STATIC PRACTICES
A ANTI-STATIC PRACTICES
This appendix only applies if you are handling a MiLLennium-GLONASS GPSCard without a ProPak II enclosure
or a PowerPak II enclosure. If you purchased either enclosure then the sections that follow are not applicable.
A.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 fibres. Electrostatic voltage levels on insulators may be very high, in the
order of thousands of volts.
Various electrical and electronic components are vulnerable to electrostatic discharge (ESD). These include
discrete components, hybrid devices, integrated circuits (ICs), and printed circuit boards (PCBs) assembled with
these devices.
A.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 or ankle
straps.
•
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 or ankle 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 an anti-static plastic clamshell before being removed
from the work location and must remain in the clamshell until it arrives at a static-controlled
repair/test center.
•
Circuit boards must not be changed or moved needlessly. Handles or finger holes 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. 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 (e.g. 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
GPS/GLONASS Receiver User Manual Rev 1
A Anti-Static Practices
47
Advertisement
Table of Contents
