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TELEDYNE INSTRUMENTS
460L Instruction Manual A Primer on Electro-Static Discharge
05228 Rev B 69
DCN 5164 PRINTED DOCUMENTS ARE UNCONTROLLED
12. A PRIMER ON ELECTRO-STATIC DISCHARGE
Teledyne Instruments considers the prevention of damage caused by the discharge of static
electricity to be extremely important part of making sure that your analyzer continues to provide
reliable service for a long time. This section describes how static electricity occurs, why it is so
dangerous to electronic components and assemblies as well as how to prevent that damage from
occurring.
12.1. How Static Charges are Created
Modern electronic devices such as the types used in the various electronic assemblies of your
analyzer, are very small, require very little power and operate very quickly. Unfortunately, the
same characteristics that allow them to do these things also make them very susceptible to
damage from the discharge of static electricity. Controlling electrostatic discharge begins with
understanding how electro-static charges occur in the first place.
Static electricity is the result of something called triboelectric charging which happens whenever
the atoms of the surface layers of two materials rub against each other. As the atoms of the two
surfaces move together and separate, some electrons from one surface are retained by the other.
+
+
Materials
Makes
Contact
PROTONS = 3
E
LECTRONS = 3
N
ET CHARGE = 0
P
ROTONS = 3
E
LECTRONS = 3
N
ET CHARGE = 0
Materials
Separate
+
PROTONS = 3
E
LECTRONS = 2
N
ET CHARGE = -1
+
PROTONS = 3
E
LECTRONS = 4
N
ET CHARGE = +1
Figure 12-1 Triboelectric Charging
If one of the surfaces is a poor conductor or even a good conductor that is not grounded, the
resulting positive or negative charge cannot bleed off and becomes trapped in place, or static.
The most common example of triboelectric charging happens when someone wearing leather or
rubber soled shoes walks across a nylon carpet or linoleum tiled floor. With each step, electrons
change places and the resulting electro-static charge builds up, quickly reaching significant levels.
Pushing an epoxy printed circuit board across a workbench, using a plastic handled screwdriver
or even the constant jostling of Styrofoam
TM
pellets during shipment can also build hefty static
charges.