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Model GFC7000E Instruction Manual A Primer on Electro-Static Discharge
04584 Rev A1 217
alligator clips are available for use in work areas where there is no available grounded
plug.
Also, anti-ESD wrist straps include a current limiting resistor (usually around one meg-
ohm) that protects you should you accidentally short yourself to the instrument’s power
supply.
•
Simply touching a grounded piece of metal is insufficient. While this may
temporarily bleed off static charges present at the time, once you stop touching the
grounded metal new static charges will immediately begin to re-build. In some conditions
a charge large enough to damage a component can rebuild in just a few seconds.
•
Always store sensitive components and assemblies in anti-ESD storage bags or
bins:
Even when you are not working on them, store all devices and assemblies in a
closed anti-Static bag or bin. This will prevent induced charges from building up on the
device or assembly and nearby static fields from discharging through the it.
•
Use metallic anti-ESD bags for storing and shipping ESD sensitive components
and assemblies rather than pink-poly bags.
The famous, pink-poly bags are made of
a plastic that is impregnated with a liquid (similar to liquid laundry detergent) which very
slowly sweats onto the surface of the plastic creating a slightly conductive layer over the
surface of the bag.
While this layer may equalizes any charges that occur across the whole bag, it does not
prevent the build up of static charges. If laying on a conductive grounded surface, these
bags will allow charges to bleed away but the very charges that build up on the surface of
the bag itself can be transferred through the bag by induction onto the circuits of your ESD
sensitive device. Also, the liquid impregnating the plastic is eventually used up after which
the bag is as useless for preventing damage from ESD as any ordinary plastic bag.
Anti-Static bags made of plastic impregnated with metal (usually silvery in color) provide
all of the charge equalizing abilities of the pink-poly bags but also, when properly sealed,
create a Faraday cage that completely isolates the contents from discharges and the
inductive transfer of static charges.
Storage bins made of plastic impregnated with carbon (usually black in color) are also
excellent at dissipating static charges and isolating their contents from field effects and
discharges.
•
Never use ordinary plastic adhesive tape near an ESD sensitive device or to close
an anti-ESD bag.
The act of pulling a piece of standard plastic adhesive tape, such as
Scotch
®
tape, from its roll will generate a static charge of several thousand or even tens of
thousands of volts on the tape itself and an associated field effect that can discharge
through or be induced upon items up to a foot away.