Dell 1135N, Service Manual

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Precautions
1-5
Service Manual
1.3 ESD Precautions
Certain semiconductor devices can be easily damaged by static electricity. Such components are commonly
called “Electrostatically Sensitive (ES) Devices” or ESDs. Examples of typical ESDs are: integrated circuits,
some field effect transistors, and semiconductor “chip” components.
The techniques outlined below should be followed to help reduce the incidence of component damage
caused by static electricity.
Caution >>Be sure no power is applied to the chassis or circuit, and observe all other safety precautions.
1. Immediately before handling a semiconductor component or semiconductor-equipped assembly, drain
off any electrostatic charge on your body by touching a known earth ground. Alternatively, employ a
commercially available wrist strap device, which should be removed for your personal safety reasons prior
to applying power to the unit under test.
2. After removing an electrical assembly equipped with ESDs, place the assembly on a conductive surface,
such as aluminum or copper foil, or conductive foam, to prevent electrostatic charge buildup in the vicinity
of the assembly.
3. Use only a grounded tip soldering iron to solder or desolder ESDs.
4. Use only an “anti-static” solder removal device. Some solder removal devices not classified as “anti-static”
can generate electrical charges sufficient to damage ESDs.
5. Do not use Freon-propelled chemicals. When sprayed, these can generate electrical charges sufficient to
damage ESDs.
6. Do not remove a replacement ESD from its protective packaging until immediately before installing it. Most
replacement ESDs are packaged with all leads shorted together by conductive foam, aluminum foil, or a
comparable conductive material.
7. Immediately before removing the protective shorting material from the leads of a replacement ESD, touch
the protective material to the chassis or circuit assembly into which the device will be installed.
8. Maintain continuous electrical contact between the ESD and the assembly into which it will be installed,
until completely plugged or soldered into the circuit.
9. Minimize bodily motions when handling unpackaged replacement ESDs. Normal motions, such as
the brushing together of clothing fabric and lifting one’s foot from a carpeted floor, can generate static
electricity sufficient to damage an ESD.