Philips CDF 100 Service Manual page 4

3.3 HANDLING ESD-SENSITIVE COMPONENTS
3.3.1 Persona! safety
The testing, handling and replacing of ESD-sensitve
components requires special attention for personal
safety. A person dealing with ESD-sensitive
components should, normally speaking, be connected
via a resistance to the same potential as the chassis
of the set to protect him against direct contact with
the supply voltage.
This resistance is often applied in the connection lead
of wrist wraps. If necessary, make use of an isolating
transformer.
3.3.2 Storage and transport
Transport and store the circuits and PCBs in their
original packages.
As an alternative to the original package one may use
a conductive material or special IC package which
short-circuits all the pins of the component with one
another.
Always discharge the package before opening it.
3.3.3 Testing or handling
Work on a conductive surface when testing loose
circuits and components or when transferring
components and circuits from one package to
another.
Use a conductive wrist wrap with lead to make an
electrical connection between the conductive surface
and yourself via a resistance in the connection lead of
the wrist wrap.
Connect equipment and tools also with this conductive
surface.
Do not connect any signals to inputs as long as the
power supply of the set to be tested is off.
All the inputs that are not used should be connected
either to ground or to the supply voltage. When
testing, do not use any freon sprays for under-cooling
of sensitive components.
3.3.4 Mounting ESD-sensitive components
Mount ESD-sensitive components only after all other
components have been mounted.
Make sure that the components themselves, the metal
parts of the PCB, mounting equipment and mounting
operator are at the same potential level as the chassis
of the set.
It it is impossible to ground the PCB, the mounting
operator should pick the PCB up before bringing it
into contact with the components to be replaced.
3.3.5 Soldering
Soldering iron tips, also those of low-voltage soldering
stations, should be kept at the same potential as the
components and the PCB.
It is better to use solder-removing braid than solder
suckers.
3.3.6 Electrostatic charges
One should stick to the precautionary measures also
after the ESD-sensitive components have been
mounted on the PCB. Until the sub-PCBs have been
incorporated into a complete system on which the
correct supply voltages are connected, the PCB is
nothing more than an extension of the conductors of
the components on this PCB. To prevent electrostatic
discharges from passing to the components via the
terminals, we recommend that you apply conductive
clips or conductive tape on the terminals of the PCB.
3.3.7 Transients (switch-on phenomena)
To prevent permanent damages as a result of
switch-on phenomena, no ESD-sensitive components,
or PCBs populated with these components, should be
inserted in or removed from test-sockets or systems
with the supply voltage on.
Prevent switching peeks on the mains as a
consequence of switching electric equipment, relay
and DC lines on and off.
3.3.8 Working environment
The work bench for the service technician should took
like the one shown in the figure.
3.3.9 Replacement of the Flat Pack IC's
For replacing a component see Fig. 6 Dismounting
and Mounting. Also a number of precautions and
examples is given.
When replacing a flat pack, rosin flux applied to the
device leads will ensure a good soldered joint.
Since rosin flux, when not properly heated by the
soldering process, is sticky, it will attract dust which
will result in component degeneration over a period of
time.
The removal of excess flux with a cleaner will not
solve this problem because the flux is then even
spread over a greater area by the cleaner. Drying of
the flux can be accomplished by blowing the area with
a common hair dryer for 1 or 2 minutes at a distance
of approx. 10 centimeters.
Special attention should be paid in regions having a
dry atmosphere and when the floor is covered with a
nylon carpet or such.
PCS 66 383