GE H
EALTHCARE
D
IRECTION
5461425-8EN, R
EVISION
B
RIVO
XR118 S
ERVICE
M
ANUAL
Chapter 1 - - Safety and Service
Page 27
Section 4.0
Equipment Safety - Electrostatic Discharge (ESD)
A sudden discharge of static electricity from your finger or other conductor can destroy static-
sensitive devices or microcircuitry. Often the spark is neither felt nor heard, but damage occurs. An
electronic device exposed to electrostatic discharge (ESD) might not appear to be affected at all
and can work perfectly throughout a normal cycle. The device can function normally for a while, but
it has been degraded in the internal layers, reducing its life expectancy.
Networks built into many integrated circuits provide some protection, but in many cases, the
discharge contains enough power to alter device parameters or melt silicon junctions.
4.1
Generating Static
The following table shows that:
•
Different activities generate different amounts of static electricity.
•
Static electricity increases as humidity decreases.
Many electronic components are sensitive to ESD. Circuitry design and structure determine the
degree of sensitivity. The following packaging and grounding precautions are necessary to prevent
damage to electric components and accessories.
•
Transport products in static-safe containers, such as tubes, bags, or boxes to avoid hand
contact.
•
Protect all electrostatic parts and assemblies with conductive or approved containers or
packaging.
•
Keep electrostatic sensitive parts in their containers until they arrive at static-free stations.
•
Place items on a grounded surface before removing them from their container.
•
When handling or touching a sensitive component or assembly, ground yourself by touching
the chassis.
•
Avoid contact with pins, leads, or circuitry.
•
Place reusable electrostatic-sensitive parts from assemblies in protective packaging or
conductive foam.
4.2
Personal Grounding Methods and Equipment
Use the following equipment to prevent static electricity damage to equipment:
•
Wrist straps are flexible straps with a maximum of one-/- 10% resistance in the
ground cords. To provide a proper ground, wear the strap against bare skin. The ground cord
must be connected and fit snugly into the banana plug connector on the grounding mat or
workstation.
Relative Humidity
Event
55%
40%
10%
Walking across carpet
7,500 V
15,000 V
35,000 V
Walking across vinyl floor
3,000 V
5,000 V
12,000 V
Motions of bench worker
400 V
800 V
6,000 V
Removing bubble pack from PCB
7,000 V
20,000 V
26,500 V
Packing PCBs in foam-lined box
5,000 V
11,000 V
21,000 V
