composed of carbon particles, impregnated in the
plastic, that provide volume conductivity throughout
the material.
Antistatic ESD-Protective Materials
Antistatic materials are normally plastic-type
materials (such as polyethylene, polyolefin,
polyurethane, and nylon) that are impregnated with an
antistatic substance. This antistatic migrates to the
surface and combines with the humidity in the air to
form a conductive sweat layer on the surface. This
layer is invisible, and although highly resistive, it is
amply conductive to prevent the buildup of
electrostatic charges by triboelectric methods in
normal handling. Simply stated, the primary asset of
an antistatic material is that it will not generate a
charge on its surface. However, this material won’t
protect an enclosed ESD device if it comes into
contact with a charged surface.
This material is of a pink tint—a symbol of its
being antistatic.
Antistatic materials are for inner-
wrap packaging.
However, antistatic trays, vials,
carriers, boxes, etc., are not used unless components
and/or assemblies are wrapped in conductive
packaging.
Hybrid ESD-Protective Bags
Lamination of different ESD-protective material
is available. This combination of conductive and
antistatic material provides the advantage of both
types in a single bag.
ESDS DEVICE HANDLING
The following are general guidelines applicable
to the handling of ESDS devices:
l Make sure that all containers, tools, test
equipment, and fixtures used in ESD-protected areas
are grounded before and during use. This may be
done either directly or by contact with a grounded
surface.
l Personnel handling ESDS items must avoid
physical activities that are friction-producing in the
vicinity of ESDS items. Some examples are putting
on or removing smocks, wiping feet, and sliding
objects over surfaces.
. Personnel handling ESDS items must wear
cotton smocks and/or other antistatically treated
clothing.
. Avoid the use or presence of plastics, synthetic
textiles, rubber, finished wood, vinyls, and other
static-generating materials (table 10-1) where ESDS
items are handled out of their ESD-protective
packaging.
l Place the ESD-protective material containing
the ESDS item on a grounded work bench surface to
remove any charge before opening the packaging
material.
. Personnel must attach personnel grounding
straps to ground themselves before removing ESDS
items from their protective packaging.
. Remove ESDS items from ESD-protective
packaging with fingers or metal grasping tool only
after grounding, and place on the ESD-grounded
work bench surface.
. Make periodic electrostatic measurements at
all
ESD-protected
areas.
This assures the
ESD-protective properties of the work station and all
equipment contained have not degraded.
. Perform periodic continuity checks of
personnel ground straps, ESD-grounded work station
surfaces, conductive floor mats, and other con-
nections to ground.
Perform this check with a
megohmmeter to make sure grounding resistivity
requirements are met.
ESDS DEVICE PACKAGING
Before an ESDS item leaves an ESD-protected
area, package the item in one of the following ESD
protective materials:
l Ensure shorting bars, clips, or noncorrective
conductive materials are correctly inserted in or on all
terminals or connectors.
l Package ESDS items in an inner wrap, of type
II material conforming to MIL-B-81705, and an outer
wrap of type I material conforming to MIL-B-81 705.
You may use a laminated bag instead of the above
provided it meets the requirements of MIL-B-81705.
Cushion-wrap the item with electrostatic-free
material conforming to PPP-C-1842, type III, style A.
Place the cushioned item into a barrier bag fabricated
from MIL-C-131 and heat-seal closed, method 1A-8.
Place the wrapped, cushioned, or pouched ESDS item
in bags conforming to MIL-B-117, type I, class F,
style I. Mark the packaged unit with the ESD symbol
and caution as shown in figure 10-15.
10-18
