Basic Protective Measures Against Static Electricity Discharges - Siemens SIROTEC Planning Manual

9.4 Basic protective measures against static electricity
discharges
Avoid charging
The best protection against the consequences of electrostatic discharging is to
prevent static electricity from developing in the environment of the exposed items.
Caution during contact with plastics
Plastics in particular should therefore be kept away from sensitive assemblies,
since most plastics can easily be statically charged.
Ensure good earthing
When using electrostatically sensitive assemblies, ensure high-impedance (200 kW
to 1 GW) earthing of humans, workplace and packaging.
Refrain from direct touching
Touch electrostatically sensitive assemblies only when it is unavoidable (e.g. to
perform work on it). Touch assemblies in such a way that you do not touch
component pins or the conducting path. In this way, the energy of the discharges
cannot reach the sensitive components and damage them.
Avoid hard discharges
If an electrostatic discharge cannot be avoided, the possibility of a smooth
discharge should be always created, e.g. via a high-impedance resistance with R >
200 kW.
Use only earthed equipment
Measure or solder electrostatically sensitive assemblies only when
·
The equipment is earthed (e.g. via a protective conductor).
·
With potential-free indicators, the measuring head is discharged before
measuring (e.g. by briefly touching earthed metal parts).
Particular caution with ESD assemblies
Please consider the following measures for assemblies with electrostatically
sensitive components which are not protected against touching by a housing and
therefore are identified appropriately (identification: See the beginning of this
chapter):
·
Touch electrostatically sensitive assemblies only
When you are earthed via an ESD wristband,
–
When you are wearing ESD shoes or an ESD earthing strip, as long as you
–
are walking on an ESD floor,
When you are not wearing man-made fibres or an ESD coat.
–
© Siemens AG, 2004. All rights reserved
EMC Installation Guideline – Planning Guide (EMV) – 03.2004 Edition
Electrostatically Sensitive Assemblies (ESA)
9-53