Dellcos Chromebook 11-3120 Disassembly And Reassembly Manual page 15

concern.
Due to the increased density of semiconductors used in recent Dell products, the sensitivity to static
damage is now higher than in earlier Dell products. For this reason some previously approved methods of
handling parts are no longer applicable.
There are two recognized types of ESD damage: catastrophic and intermittent failures.
Catastrophic —The damage causes an immediate and complete loss of device functionality. An
example of catastrophic failure is a memory DIMM that has received a static shock and immediately
generates a "No POST/No Video" symptom with a beep code emitted for missing or nonfunctional
memory.
NOTE: Catastrophic failures represent approximately 20 percent of ESD-related failures.
Intermittent —The DIMM receives a static shock, but the tracing is merely weakened and does not
immediately produce outward symptoms related to the damage. The weakened trace may take
weeks or months to melt, and in the meantime may cause degradation of memory integrity,
intermittent memory errors, etc.
NOTE: Intermittent failures represent approximately 80 percent of ESD-related failures. The
high rate of intermittent failures means that most of the time when damage occurs, it is not
immediately recognizable.
The more difficult type of damage to recognize and troubleshoot is the intermittent (also called latent or
"walking wounded") failure. The following image shows an example of intermittent damage to a memory
DIMM trace. Although the damage is done, the symptoms may not become an issue or cause permanent
failure symptoms for some time after the damage occurs.
Intermittent (Latent) Damage to a Wiring Trace
Do the following to prevent ESD damage:
Use a wired ESD wrist strap that is properly grounded.
The use of wireless anti-static straps is no longer allowed; they do not provide adequate protection.
Touching the chassis before handling parts does not ensure adequate ESD protection on parts with
increased sensitivity to ESD damage.
Chassis "Bare Metal" Grounding (Unacceptable)
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