User's Manual

Devices sensitiv e to static
Devices sensitive to static
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Certain metal oxide semiconductor (MOS) devices embody in their design a thin layer of
insulation that is susceptible to damage from electrostatic charge. Such a charge applied to the
leads of the device could cause irreparable damage.
These charges can be built up on nylon overalls, by friction, by pushing the hands into high
insulation packing material or by use of ungrounded soldering irons.
MOS devices are normally despatched from the manufacturers with the leads short circuited
together , for example, by metal foil eyelets, wire strapping, or by inserting the leads into
conductive plastic foam. Provided the leads are short circuited it is safe to handle the device.
Special handling techniques
In the event of one of these devices having to be replaced, observe the following precautions
when handling the replacement:
• Always wear a ground strap which must be connected to the electrostatic point on the
equipment.
• Leave the short circuit on the leads until the last moment. It may be necessary to replace
the conductive foam by a piece of wire to enable the device to be fitted.
• Do not wear outer clothing made of nylon or similar man made material. A cotton overall
is preferable.
• If possible work on an grounded metal surface or anti -static mat. W ipe insulated plastic
work surfaces with an anti -static cloth before starting the operation.
• All metal tools should be used and when not in use they should be placed on an grounded
surface.
• T ake care when removing components connected to electrostatic sensitive devices. These
components may be providing protection to the device.
When mounted onto printed circuit boards (PCBs), MOS devices are normally less susceptible to
electrostatic damage. However PCBs should be handled with care, preferably by their edges
and not by their tracks and pins, they should be transferred directly from their packing to the
equipment (or the other way around) and never left exposed on the workbench.
68P09277A59 -5 11
OCT 2006 Draft