Generating Static; Preventing Electrostatic Damage To Equipment - Compaq Armada e500s Maintenance And Service Manual

Generating Static

Table 4-1 shows how different activities generate static electricity and at different
electrostatic voltage levels.
Event
Walking across carpet
Walking across vinyl floor
Motions of bench worker
Removing DIPS from plastic tube
Removing DIPS from vinyl trays
Removing DIPS from Styrofoam
Removing bubble pack from PCBs
Packing PCBs in foam-lined box
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 ground
precautions are necessary to prevent damage.
Protect all electrostatic sensitive parts and assemblies with nonconductive 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.
Place reusable electrostatic-sensitive parts from assemblies in protective packaging
or nonconductive foam.
Use transporters and conveyers made of antistatic belts and roller bushings. Mechanized
equipment used for moving materials must be wired to ground and proper materials
selected to avoid static charging. When grounding is not possible, use an ionizer to
dissipate electric charges.
4-2 Removal and Replacement Preliminaries
Table 4-1
Typical Electrostatic Voltages
10%
35,000 V
12,000 V
6,000 V
2,000 V
11,500 V
14,500 V
26,000 V
21,000 V
Relative Humidity
40% 55%
15,000 V 7,500 V
5,000 V 3,000 V
800 V 400 V
700 V 400 V
4,000 V 2,000 V
5,000 V 3,500 V
20,000 V 7,000 V
11,000 V 5,000 V