9
Electrostatic Discharge (ESD) Precautions
9.1
What is Static Electricity?
Static electricity is generated when two materials move against one another. The
voltage generated depends on the materials generating the electricity, the speed of
movement, humidity and rate of discharge. All man made materials generate static,
such as plastic coffee cups, plastic bags, binders and folders, all of which are likely to
be within the working area.
Activity
10-20% Relative Humidity
Walking across carpet
35,000 Volts
Walking across vinyl floor
12,000 Volts
Working at bench
6,000 Volts
Plastic folder
7,000 Volts
Poly bag lifted from bench
20,000 Volts
Foam padded work chair
18,000 Volts
Static electricity is generated very easily, and is only felt by us when we discharge the
built up charge rapidly by touching a grounded object such as a grounded door
handle. The voltages felt by us are as high as 3kV, but only 20V is necessary to
damage some components. Voltages as high as 35kV and current spikes of 40A have
been known.
The damage to the component, or assembly can be immediate or latent. Latent
damage is not immediately obvious but can lead to the circuitry subsequently failing
or becoming erratic.
9.2
Protective Measures
To protect devices (ESDs) from the unwanted effects of ESD, two key measures must
be taken to minimise the possibility of damage.
1. All sensitive devices and assemblies must be handled in an ESD Protected
Area (EPA).
2. All sensitive devices and assemblies must be transported in a protected state.
For further information on static precautions and soldering equipment refer to
Appendix A.
36
Issue: 2 Draft
Rev: a
614365
