85
240PW9 LCD

0. Warning

AllICs and many other semi-conductors aresusceptible to
electrostatic discharges (ESD). Careless handlingduring
repair can reducelife drastically. When repairing, make sure
thatyou are connected with the same potentialas the mass
ofthe unitvia a wrist wrap with resistance. Keep components
and tools also at the same potential !

1. Servicing ofSMDs (Surface Mounted Devices)

1.1 General cautions on handling and storage
- Oxidation on the terminals of SMDs results in poor soldering.
Do not handle SMDs withbare hands.
- Avoid using storage places that are sensitive tooxidation
such as places withsulphur or chlorine gas, direct sunlight,
hightemperatures or a high degree of humidity. The
capacitance or resistance value of the SMDs may be
affected by this.
- Rough hand ling of circuit boards containing SMDs may
cause damage to the components as well as the circuit
boards. Circuit boards containing SMDs should never be
bentor 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 chipcomponents as
this may cause the value of the component to change.
Similarly, do not slide the circuit board across any surface.
1.2 Removal of SMDs
- Heat the solde r (for 2- 3 seconds) at each terminal of the
chip. By means oflitz wire and a slight horizontal force,
small components can be removed withthe soldering iron.
They can also be removed with a solder sucker (see Fig.
1A)
While holding the SMD witha pair of tweezers, take it off gently using the
soldering iron's heat applied toeach terminal(see Fig. 1 B).
-Remove theexcess solder on the solder lands by means of
litzwire or a solder sucker (see Fig. 1C).
1.3 Caution on removal
-When handling thesoldering.iron. use suitable pressure and be careful.
-When removing thechip, do not use undue force with the pair of tweezers.
-The soldering iron to be used (approx. 30 W) should
preferably be equipped with a thermal control (soldering
temperature: 225 to 250 C).
- The chip, once removed, must never be reused.

1.4 Attachment of SMDs

- Locate the SMD onthe solder lands by means of tweezers
and solder the component on one side. Ensure thatthe
component is positioned cor rectly on the solder lands (see Fig.2A).
- Next complete the soldering of the terminals of the
component (see Fiq. 2B).

2. Caution when attaching SMDs

-When soldering the SMD terminals, do not touch them
directly withthe 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 toogreat, the SMD might
crack or the solder lands might be torn loose from the
printedboard (see Fig. 3).
Fig.3 Examples
Right
Repair Tips