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Compaq Deskpro EP Series of Personal Computers 3-3
3.2 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 be
affected at all and can work perfectly throughout a normal cycle. The device 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.
3.2.1 Generating Static
The following table shows that different activities generate different amounts of static
electricity, and that static electricity increases as humidity decreases.
✎
700 volts can degrade a product.
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 tube 2,000 V 700 V 400 V
Removing DIPs* from vinyl tray 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 PCB 26,500 V 20,000 V 7,000 V
Packing PCBs in foam-lined box 21,000 V 11,000 V 5,000 V
*Dual Inline Packaging (DIP) is the packaging around individual microcircuitry. These are then
multi-packaged inside plastic tubes, trays, or Styrofoam.
3.2.2 Preventing Electrostatic Damage to Equipment
Many electronic components are sensitive to ESD. Circuitry design and structure
determine the degree of sensitivity. The following proper 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.
!
Avoid contact with pins, leads, or circuitry.
! Place reusable electrostatic-sensitive parts from assemblies in protective packaging
or conductive foam.