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Repair Tips 107B2 CM24 GSIII 27
9 Go to cover page
0. Warning preferably be equipped with a thermal control (soldering
temperature: 225 to 250 C).
All ICs and many other semi-conductors are susceptible to - The chip, once removed, must never be reused.
electrostatic discharges (ESD). Careless handling during
repair can reduce life drastically. When repairing, make sure 1.4 Attachment of SMDs
that you are connected with the same potential as the mass - Locate the SMD on the solder lands by means of tweezers
of the unit via a wrist wrap with resistance. Keep components and solder the component on one side. Ensure that the
and tools also at the same potential ! component is positioned correctly on the solder lands (see
- Next complete the soldering of the terminals of the
1. Servicing of SMDs (Surface Mounted Devices) component (see Fiq. 2B).
1.1 General cautions on handling and storage Fig. 2 MOUNTING
- Oxidation on the terminals of SMDs results in poor soldering. e.g. A PAIR OF TWEEZERS
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, A
high temperatures or a high degree of humidity. The
capacitance or resistance value of the SMDs may be 0.5 - 0.8 mm
affected by this. SOLDERING
- Rough handling of circuit boards containing SMDs may IRON
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 SOLDERING TIME
< 3 sec/side
0.5 - 0.8 mm B
contract at different rates when heated or cooled and the PRESURE
components and/or solder connections may be damaged IRON
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.
2. Caution when attaching SMDs
1.2 Removal of SMDs - When soldering the SMD terminals, do not touch them
- Heat the solder (for 2-3 seconds) at each terminal of the directly with the soldering iron. The soldering should be
chip. By means of litz wire and a slight horizontal force, done as quickly as possible, care must be taken to avoid
small components can be removed with the soldering iron. damage to the terminals of the SMDs themselves.
They can also be removed with a solder sucker (see Fig. - Keep the SMD's body in contact with the printed board when
Fig. 1 DISMOUNTING
- The soldering iron to be used (approx. 30 W ) should
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preferably be equipped with a thermal control (soldering
temperature: 225 to 250 C).
e.g. WELLER - Soldering should not be done outside the solder land.
SOLDER TIP PT -H7
A - Soldering flux (of rosin) may be used, but should not be
IRON - After soldering, let the SMD cool down gradually at room
SOLDER WICK temperature.
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- The quantity of solder must be proportional to the size of the
e.g. A PAIR OF TWEEZERS
solder land. If the quantity is too great, the SMD might
HEATING HEATING crack or the solder lands might be torn loose from the
B printed board (see Fig. 3).
SOLDERING Fig. 3 Examples
- 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).
1.3 Caution on removal
- When handling the soldering.iron. use suitable pressure and SOLDERING
- When removing the chip, do not use undue force with the
pair of tweezers.
- The soldering iron to be used (approx. 30 W) should