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SAFE HANDLING OF CMOS INTEGRATED CIRCUIT DEVICES
Many of the integrated circuit devices used in
communications equipment are of the CMOS
(Complementary
Semiconductor) type. Because of their high
open circuit impedance, CMOS ICs are
vulnerable to damage from static charges.
Care must be taken in handling, shipping, and
servicing them and the assemblies in which
they are used.
Even though protection devices are provided
in CMOS IC inputs, the protection is effective
only against overvoltage in the hundreds of
volts range such as are encountered in an
operating system.
elements distribute static charges and load the
CMOS circuits, decreasing the chance of
damage.
However, CMOS circuits can be
damaged by improper handling of the
modules even in a system.
To avoid damage to circuits, observe the
following handling, shipping, and servicing
precautions.
1. Prior to and while servicing a circuit
module, particularly after moving within
the service area, momentarily touch both
hands to a bare metal earth grounded
surface. This will discharge any static
charge which may have accumulated on
the person doing the servicing.
NOTE
Wearing Conductive Wrist Strap will
minimize static buildup during servicing.
Metal
Oxide
In a system, circuit
Appendix C
When wearing Conductive Wrist Strap, be
careful near sources of high voltage. The
good ground provided by the wrist strap
will also increase the danger of lethal
shock from accidentally touching high
voltage sources.
2. Whenever possible, avoid touching any
electrically conductive parts of the
circuit module with your hands.
3. Normally, circuit modules can be
inserted or removed with power applied
to the unit. However, check the
INSTALLATION
NANCE sections of the manual as well
as the module schematic diagram to
insure there are no objections to this
practice.
4. When servicing a circuit module, avoid
carpeted areas, dry environments, and
certain types of clothing (silk, nylon,
etc.) because they contribute to static
buildup.
5. All electrically powered test equipment
should be grounded. Apply the ground
lead from the test equipment to the
circuit module before connecting the test
probe. Similarly, disconnect the test
probe prior to removing the ground lead.
6. If a circuit module is removed from the
system, it is desirable to lay it on a
conductive surface (such as a sheet of
aluminum foil) which is connected to
ground through 100k of resistance.
C-1
WARNING
and
MAINTE-
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