01671H (DCN6051) 8-1
8 A PRIMER ON ELECTRO-STATIC DISCHARGE
Teledyne API 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.

8.1 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
ELECTRONS = 3
NET CHARGE = 0
PROTONS = 3
ELECTRONS = 3
NET CHARGE = 0
Materials
Separate
+
PROTONS = 3
ELECTRONS = 2
NET CHARGE = -1
+
PROTONS = 3
ELECTRONS = 4
NET CHARGE = +1
Figure 8-1: 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 StyrofoamTM pellets during shipment can also build hefty static
charges