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Repair Tips 109B2 GS3 CM25 29
26
9 Go to cover page
0. Warning 1.4 Attachment of SMDs
- Locate the SMD on the solder lands by means of tweezers and
All ICs and many other semi-conductors are susceptible to solder the component on one side. Ensure that the component is
electrostatic discharges (ESD). Careless handling during repair can Positioned correctly on the solder lands (see Fig.2A).
reduce life drastically. When repairing, make sure that you are - Next complete the soldering of the terminals of the component (see
connected with the same potential as the mass of the unit via a wrist Fig. 2B).
wrap with resistance. Keep components and tools also at the same
potential !
Fig. 2 MOUNTING

e.g. A PAIR OF TWEEZERS
1. Servicing of SMDs (Surface Mounted Devices)

1.1 General cautions on handling and storage A
- Oxidation on the terminals of SMDs results in poor soldering. Do not
handle SMDs with bare hands. SOLDER
0.5 - 0.8 mm
- Avoid using storage places that are sensitive to oxidation such as PRESURE
places with sulphur or chlorine gas, direct sunlight, high SOLDERING
IRON
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 SOLDERING TIME SOLDER
B
< 3 sec/side 0.5 - 0.8 mm
boards containing SMDs should never be bent or flexed. Different PRESURE
circuit board materials expand and contract at different rates when SOLDERING
IRON
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.
2. Caution when attaching SMDs
1.2 Removal of SMDs
- Heat the solder (for 2-3 seconds) at each terminal of the chip. By - When soldering the SMD terminals, do not touch them directly with
means of litz wire and a slight horizontal force, small components the soldering iron. The soldering should be done as quickly as
can be removed with the soldering iron. They can also be removed possible, care must be taken to avoid damage to the terminals of
with a solder sucker (see Fig. 1A) the SMDs themselves.
- Keep the SMD's body in contact with the printed board when
soldering.
Fig. 1 DISMOUNTING - The soldering iron to be used (approx. 30 W ) should preferably be
VACUUM PISTON
equipped with a thermal control (soldering temperature: 225 to 250
SOLDERING 4822 395 10159 o
C).
IRON
- Soldering should not be done outside the solder land.
e.g. WELLER
SOLDER TIP PT -H7
- Soldering flux (of rosin) may be used, but should not be acidic.
A - After soldering, let the SMD cool down gradually at room
temperature.
SOLDERING
IRON - The quantity of solder must be proportional to the size of the solder
SOLDER WICK
land. If the quantity is too great, the SMD might crack or the solder
4822 321 40042 lands might be torn loose from the printed board (see Fig. 3).
e.g. A PAIR OF TWEEZERS


HEATING HEATING

B Fig. 3 Examples

SOLDERING
IRON
C
SOLDER WICK RIGHT




- 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). SOLDERING
IRON

1.3 Caution on removal
- 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 preferably be
equipped with a thermal control (soldering temperature: 225 to 250
o
C).
- The chip, once removed, must never be reused.




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