HP Compaq Compaq dx2290, Service & Reference Manual

Page: 29 / 81

Generating Static
The following table shows that:
●
Different activities generate different amounts of static electricity.
●
Static electricity increases as humidity decreases.
Relative Humidity
Event 55% 40% 10%
Walking across carpet
Walking across vinyl floor
Motions of bench worker
Removing DIPs* from plastic tube
7,500 V
3,000 V
400 V
400 V
15,000 V
5,000 V
800 V
700 V
35,000 V
12,000 V
6,000 V
2,000 V
Removing DIPs* from vinyl tray
Removing DIPs* from Styrofoam
Removing bubble pack from PCB
Packing PCBs in foam-lined box
2,000 V
3,500 V
7,000 V
5,000 V
4,000 V
5,000 V
20,000 V
11,000 V
11,500 V
14,500 V
26,500 V
21,000 V
*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 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.
Personal Grounding Methods and Equipment
Use the following equipment to prevent static electricity damage to equipment:
● Wrist straps are flexible straps with a maximum of one-megohm ± 10% resistance in the ground
cords. To provide proper ground, a strap must be worn snug against bare skin. The ground cord
must be connected and fit snugly into the banana plug connector on the grounding mat or
workstation.
Electrostatic Discharge Information 21