Teledyne GFC-7001T - Trace CO Analyzer - Manual (Page 317)

Teledyne - Technical Manual - Model T300 Family CO Analyzers ESD
Teledyne Analytical Instruments 317
 Any time a charged surface (including the human body) discharges to a
device. Even simple contact of a finger to the leads of a sensitive device or
assembly can allow enough discharge to cause damage. A similar discharge
can occur from a charged conductive object, such as a metallic tool or
fixture.
 When static charges accumulated on a sensitive device discharges from the
device to another surface such as packaging materials, work surfaces,
machine surfaces or other device. In some cases, charged device discharges
can be the most destructive.
 A typical example of this is the simple act of installing an electronic
assembly into the connector or wiring harness of the equipment in which it
is to function. If the assembly is carrying a static charge, as it is connected
to ground a discharge will occur.
 Whenever a sensitive device is moved into the field of an existing electro-
static field, a charge may be induced on the device in effect discharging the
field onto the device. If the device is then momentarily grounded while
within the electrostatic field or removed from the region of the electrostatic
field and grounded somewhere else, a second discharge will occur as the
charge is transferred from the device to ground.
14.3. COMMON MYTHS ABOUT ESD DAMAGE
 I didn’t feel a shock so there was no electro-static discharge: The human
nervous system isn’t able to feel a static discharge of less than 3500 volts.
Most devices are damaged by discharge levels much lower than that.
 I didn’t touch it so there was no electro-static discharge: Electro Static
charges are fields whose lines of force can extend several inches or
sometimes even feet away from the surface bearing the charge.
 It still works so there was no damage: Sometimes the damaged caused by
electro-static discharge can completely sever a circuit trace causing the
device to fail immediately. More likely, the trace will be only partially
occluded by the damage causing degraded performance of the device or
worse, weakening the trace. This weakened circuit may seem to function
fine for a short time, but even the very low voltage and current levels of the
device’s normal operating levels will eat away at the defect over time
causing the device to fail well before its designed lifetime is reached.
 These latent failures are often the most costly since the failure of the
equipment in which the damaged device is installed causes down time, lost
data, lost productivity, as well as possible failure and damage to other pieces
of equipment or property.
 Static Charges can’t build up on a conductive surface: There are two errors
in this statement.
 Conductive devices can build static charges if they are not grounded. The
charge will be equalized across the entire device, but without access to earth
ground, they are still trapped and can still build to high enough levels to
cause damage when they are discharged.
 A charge can be induced onto the conductive surface and/or discharge
triggered in the presence of a charged field such as a large static charge