Compaq Presario 5700 Series - Page 10

Fax/Modem
Networking Interface Card
Memory
Processor
Processor Retention Clips
RTC Battery
System Board Cables
System Board
Parallel Port
Back I/O Panel
Power Supply
Electrostatic Discharge
A sudden discharge of static electricity from a 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 be
affected at all and will work perfectly throughout a normal cycle. Or it may function
normally for a while, then degrade 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.
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Generating Static
The accompanying table shows typical electrostatic voltages generated by different
activities.
Typical Electrostatic Voltages
Relative Humidity
Event 10% 40% 55%
Walking across carpet 35,000 V 15,000 V 7,500 V
Walking across vinyl floor 12,000 V 5,000 V 3,000 V
Motions of bench worker 6,000 V 800 V 400 V
Removing DIPS from plastic tubes 2,000 V 700 V 400 V
Removing DIPS from vinyl trays 11,500 V 4,000 V 2,000 V
Removing DIPS from Styrofoam 14,500 V 5,000 V 3,500 V
Removing bubble pack from PCBs 26,000 V 20,000 V 7,000 V
Packing PCBs in foam-lined box 21,000 V 11,000 V 5,000 V
NOTE: 700 volts can degrade a product.
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