Philips 170C4FS/00, Service Manual

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32 170C4/N4
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0. Warning
1. Servicing of SMDs (Surface Mounted Devices)
All ICs and many other semi-conductors are susceptible to
electrostatic discharges (ESD). Careless handling during
repair can reduce life drastically. When repairing, make sure
that you are connected with the same potential as the mass
of the unit via a wrist wrap with resistance. Keep components
and tools also at the same potential !
- Oxidation on the terminals of SMDs results in poor
soldering. Do not handle SMDs with bare hands.
- Avoid using storage places that are sensitive to oxidation
such as places with sulphur or chlorine gas, direct sunlight,
high temperatures or a high degree of humidity. The
capacitance or resistance value of the SMDs may be
affected by this.
- Rough handling of circuit boards containing SMDs may
cause damage to the components as well as the circuit
boards. Circuit boards containing SMDs should never be
bent or flexed. Different circuit board materials expand and
contract at different rates when heated or cooled and the
components and/or solder connections may be damaged
due to the stress. Never rub or scrape chip components as
this may cause the value of the component to change.
Similarly, do not slide the circuit board across any surface.
- Heat the solder (for 2-3 seconds) at each terminal of the
chip. By means of litz wire and a slight horizontal force,
small components can be removed with the soldering iron.
They can also be removed with a solder sucker (see Fig.
1A)
- While holding the SMD with a pair of tweezers, take it off
gently using the soldering iron's heat applied to each
terminal (see Fig. 1 B).
- Remove the excess solder on the solder lands by means of
litz wire or a solder sucker (see Fig. 1C).
- When handling the soldering.iron. use suitable pressure and
be careful.
- When removing the chip, do not use undue force with the
pair of tweezers.
- The soldering iron to be used (approx. 30 W) should
1.1 General cautions on handling and storage
1.2 Removal of SMDs
1.3 Caution on removal
preferably be equipped with a thermal control (soldering
temperature: 225 to 250 C).
- The chip, once removed, must never be reused.
o
1.4 Attachment of SMDs
- Locate the SMD on the solder lands by means of tweezers
and solder the component on one side. Ensure that the
component is positioned correctly on the solder lands (see
Fig.2A).
- Next complete the soldering of the terminals of the
component (see Fiq. 2B).
- When soldering the SMD terminals, do not touch them
directly with the soldering iron. The soldering should be
done as quickly as possible, care must be taken to avoid
damage to the terminals of the SMDs themselves.
- Keep the SMD's body in contact with the printed board when
soldering.
- The soldering iron to be used (approx. 30 W ) should
preferably be equipped with a thermal control (soldering
temperature: 225 to 250 C).
- Soldering should not be done outside the solder land.
- Soldering flux (of rosin) may be used, but should not be
acidic.
- After soldering, let the SMD cool down gradually at room
temperature.
- The quantity of solder must be proportional to the size of the
solder land. If the quantity is too great, the SMD might
crack or the solder lands might be torn loose from the
printed board
(see Fig. 3).
2. Caution when attaching SMDs
o
SOLDERING
IRON
RIGHT
Fig. 3 Examples
DISMOUNTING
VACUUM PISTON
4822 395 10159
SOLDERING
IRON
e.g. WELLER
SOLDER TIP PT -H7
SOLDERING
IRON
SOLDER WICK
4822 321 40042
SOLDERING
IRON
SOLDER WICK
e.g. A PAIR OF TWEEZERS
HEATING
HEATING
Fig. 1
A
B
C
e.g. A PAIR OF TWEEZERS
SOLDER
0.5 - 0.8 mm
SOLDER
0.5 - 0.8 mm
SOLDERING
IRON
SOLDERING TIME
< 3 sec/side
SOLDERING
IRON
PRESURE
PRESURE
MOUNTING
Fig. 2
B
A
Repair Tips
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