Generating static
The following table shows that different activities generate different amounts of static electricity. Static
electricity increases as humidity decreases.
Table 5-1 Static electricity
Relative Humidity
Event
5% 4% 1%
Walking across carpet
Walking across vinyl floor
Motions of bench worker
7,500 V
3,000 V
400 V
15,000 V
5,000 V
800 V
35,000 V
12,000 V
6,000 V
Removing bubble pack from PCB
Packing PCBs in foam-lined box
7,000 V
5,000 V
20,000 V
11,000 V
26,500 V
21,000 V
CAUTION: 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.
●
Transport products in static-safe containers, such as tubes, bags, or boxes, to avoid hand contact.
●
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.
●
When handling or touching a sensitive component or assembly, ground yourself by touching the
chassis.
●
Avoid contact with pins, leads, or circuitry.
●
Place reusable electrostatic-sensitive parts from assemblies in protective packaging or conductive
foam.
52 Chapter 5 Removal and replacement procedures ENWW
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