performing work-around procedures in recon-
ciling differences in equipment and program mode
Learning Objective: Recognize the hazards
status, and in the verification of repairs.
to ESD-sensitive devices, to include proper
handling and packaging techniques.
In the manual mode, the test station is
completely off-line with respect to the computer.
The sensitivity of electronic devices and
Instructions come from the operator through the
components to electrostatic discharge (ESD) has
keyboard on a one-word-at-a-time basis. (See
recently become clear through use, testing and
failure analysis. The construction and design
mode for avionics testing, it is useful for
features of current microtechnology have resulted
debugging new programs. You can also integrate
in devices being destroyed or damaged by ESD
new building blocks into the station, and perform
voltages as low as 20 volts. The trend in this
self-check operations on some of the building
technology is toward greater complexity, increased
blocks using this mode.
packaging density, and thinner dielectrics between
active elements. This trend will result in devices
even more sensitive to ESD.
Various devices and components are suscepti-
ble to damage by electrostatic voltage levels
commonly generated in production, test, and
operation, and by maintenance personnel. These
devices and components include the following:
All microelectronic and most semicon-
ductor devices, except for various power
Thick and thin film resistors, chips and
hybrid devices, and crystals
All subassemblies, assemblies, and equipment
containing these components/devices without
adequate protective circuitry are ESD sensitive.
You can protect ESDS items by implementing
simple, low-cost ESD controls. Lack of imple-
mentation has resulted in high repair costs,
excessive equipment downtime, and reduced
The operational characteristics of a system
may not normally show these failures. However,
under internal built-in-test monitoring in a
digital application, they become pronounced, For
example, the system functions normally on the
ground; but, when placed in an operational
environment, a damaged PN junction might
further degrade, causing its failure. Normal
examination of these parts will not detect the
damage unless you use a curve tracer to measure
the signal rise and fall times, or check the parts
for reverse leakage current.
Some substances readily give up electrons while
Figure 2-43.-VAST control panel.