3-2
Compaq Professional Workstation SP750 Maintenance and Service Guide
Generating Static
The following table shows that:
■
Different activities generate different amounts of static electricity.
■
Static electricity increases as humidity decreases.
Table 3-1
Generating Static
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 DIPs* from plastic tube 400 V 700 V 2,000 V
Removing DIPs* from vinyl tray 2,000 V 4,000 V 11,500 V
Removing DIPs* from Styrofoam
3,500 V 5,000 V 14,500 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
* Dual Inline Packaging (DIP) is the packaging around individual microcircuitry.
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 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 containers.
■
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.
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