Common Myths About Esd Damage - Teledyne T100 Instruction Manual


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.

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.

11.3. 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.

Static Charges can't build up on a conductive surface: There are two errors in this statement.
Schottky TTL
Potentially damaging electro-static discharges can occur:
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.
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.
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
500 2500