Filter
Top Products
Removal and Replacement
Procedures
Service Considerations 75
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) might not appear to be affected at all and can work
perfectly throughout a normal cycle. The device can function normally for a while, but it has been
degraded 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.
Generating Static
The following table shows that:
• Different activities generate different amounts of static electricity.
• Static electricity increases as humidity decreases.
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 container.
• 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.
Table 4-16 Static Electricity
Relative Humidity
Event 55% 40% 10%
Walking across carpet
Walking across vinyl floor
Motions of bench worker
7, 5 0 0 V
3,000V
400V
15,000V
5,000V
800V
35,000V
12,000V
6,000V
Removing bubble pack from PCB
Packing PCBs in foam-lined box
7,000V
5,000V
20,000V
11,000V
26,500V
21,000V
NOTE: 700V can degrade a product.