Grounding Guidelines; Electrostatic Discharge Damage - HP EliteBook 8740W Maintenance And Service Manual

Grounding guidelines

Electrostatic discharge damage

Electronic components are sensitive to electrostatic discharge (ESD). Circuitry design and structure
determine the degree of sensitivity. Networks built into many integrated and pointing stick circuits
provide some protection, but in many cases, ESD contains enough power to alter device parameters
or melt silicon junctions.
A discharge of static electricity from a finger or other conductor can destroy static-sensitive devices or
microcircuitry. Even if the spark is neither felt nor heard, damage may have occurred.
An electronic device exposed to ESD may not be affected at all and and pointing stick can work
perfectly throughout a normal cycle. Or the device may function normally for a while, then degrade in
the internal layers, reducing its life expectancy.
CAUTION:
components, observe these precautions:
Keep components in their electrostatic-safe containers until you area ready to install them.
Use nonmagnetic tools.
Before touching an electronic component, discharge static electricity by using the guidelines
described in this section.
Avoid touching pins, leads, and and pointing stick circuitry. Handle electronic components as little as
possible.
If you remove a component, place it in an electrostatic-safe container.
The following table shows how humidity affects the electrostatic voltage levels generated by different
activities.
CAUTION:
Event
Walking across carpet
Walking across vinyl floor
Motions of bench worker
Removing DIPS from plastic tube
Removing DIPS from vinyl tray
Removing DIPS from Styrofoam
Removing bubble pack from PCB
Packing PCBs in foam-lined box
ENWW
To prevent damage to the computer when you are removing or installing internal
A product can be degraded by as little as 700 V.
Typical electrostatic voltage levels
10%
35,000 V
12,000 V
6,000 V
2,000 V
11,500 V
14,500 V
26,500 V
21,000 V
Relative humidity
40%
15,000 V
5,000 V
800 V
700 V
4,000 V
5,000 V
20,000 V
11,000 V
Preliminary replacement requirements
55%
7,500 V
3,000 V
400 V
400 V
2,000 V
3,500 V
7,000 V
5,000 V
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