Chapter 1 – Introduction
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Risks created by an electrostatic discharge
A high ESD voltage (several thousand volts) creates danger for electronic components. A semi-conductor
must be handled carefully to prevent destruction by ESD. ESD are truly dangerous. It is estimated that they
destroy only 10% of the components that they effect. The other 90% of components fall into the
"deteriorated" category. A component may be damaged with simply 25% of the voltage required to destroy
it.
These hidden faults can lead to problems that appear several days, weeks or even months after the
incident. Components may also undergo a change in their operating characteristics. Initial tests are
successfully passed but an intermittent error occurs under vibration or temperature constraints. The same
components will pass the "on/off" test successfully, as carried out during repairs, but the problem will
reappear again once on site.
Typical ESD voltages
Source
Low relative
humidity
10 - 20%
Average relative
humidity
40%
High relative
humidity
65 - 90%
Walking on carpet 35 kV 15 kV 1,5 kV
Walking on vinyl 12 kV 5 kV 0,3 kV
Working at the
workstation
6 kV 2,5 kV 0,1 kV
Plastified instructions 7 kV 2,6 kV 0,6 kV
Polyethylene bags 20 kV 2 kV 1,2 kV
Cellular polyurethane 18 kV 11 kV 1,5 kV
Charge sources
Work surfaces Packaging
Floors Handling
Chairs Assembly
Carriages Cleaning
Clothes Repairing
Parts sensitive to static charges
Electronic cards
Power supplies
Encoders
etc
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