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Teledyne API T802 Paramagnetic O
2
Analyzer Operation Manual A Primer on Electro-Static Discharge
243
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 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 equalize 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.
07275B DCN6418