AN055
ESD Static Protection Manual
10
2.
ESD Protected Area EPA
ESD/EOS safety benches prevent damage to sensitive components from electrostatic
discharges and spikes generated during operation. The safety workbench should have the
protection function against EOS damage and avoid the spikes pulse generated by test
equipment such as maintenance, production, and testing. Soldering irons, tweezers, and test
equipment can generate enough power to destroy extremely sensitive components and
degrade the performance of other components.
In order to be ESD protected, a ground path must be provided to neutralize static charges,
which can otherwise discharge on devices and assemblies and cause damage. Therefore,
the ESD safe workbench EPA also has a grounded static dissipative or antistatic surface. It
also provides a grounding path for the operator's skin to eliminate static electricity generated
on the skin and clothes. Generally, it is suggested to wear an anti-static wristband.
Measures must be taken in the grounding system to prevent damage to the operator's body
and the chip due to the current generated by carelessness or equipment failure. Generally, a
resistor is connected to the ground path. Changing the resistor will slow down the decay time
and prevent current spikes from electrostatic sources. In addition, the power supply voltage
used must be checked, and appropriate protection should be considered on the workbench
to prevent personnel from being injured by electrical overstress. The maximum grounding
resistance and discharge time allowed for electrostatic safe operation, please refer to
2-1. Maximum Ground Resistance and Discharge Time Allowed for Electrostatic Safe
Table 2-1. Maximum Ground Resistance and Discharge Time Allowed for Electrostatic
Safe Operation
Operators to the ground
through the medium
Maximum allowable
resistance
Maximum acceptable
discharge time
From floor mat to ground
1000M
Ω
< 1s
From desk mat to ground
1000M
Ω
< 1s
From wristband to ground
100M
Ω
< 0.1s
An example of an acceptable workbench is shown in
Figure 2-1. Series connection and
parallel connection of anti-static wristbands
. When necessary, an air ionizer may be
required in more sensitive applications. The selection, placement and use of the ionizer must
ensure its effectiveness.
