HP Compaq dx2308, Service & Reference Manual

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Electrostatic Discharge Information
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) may not appear to be affected at all and can work perfectly
throughout a normal cycle. The device may 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.
Generating Static
The following table shows that:
●
Different activities generate different amounts of static electricity.
● Static electricity increases as humidity decreases.
Relative Humidity
Event 55% 40% 10%
Walking across carpet
Walking across vinyl floor
Motions of bench worker
Removing DIPs* from plastic tube
7,500 V
3,000 V
400 V
400 V
15,000 V
5,000 V
800 V
700 V
35,000 V
12,000 V
6,000 V
2,000 V
Removing DIPs* from vinyl tray
Removing DIPs* from Styrofoam
Removing bubble pack from PCB
Packing PCBs in foam-lined box
2,000 V
3,500 V
7,000 V
5,000 V
4,000 V
5,000 V
20,000 V
11,000 V
11,500 V
14,500 V
26,500 V
21,000 V
*These are then multi-packaged inside plastic tubes, trays, or Styrofoam.
NOTE: 700 volts can degrade a product.
Preventing Electrostatic Damage to Equipment
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.
●
To avoid hand contact, transport products in static-safe containers such as tubes, bags, or boxes.
●
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.
●
Always be properly grounded when touching a sensitive component or assembly.
ENWW Electrostatic Discharge Information 29