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0. Warning
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 !
1. Servicing of SMDs (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 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.
1.2 Removal of SMDs
- 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)
Fig. 1
DISMOUNTING
SOLDERING
IRON
e.g. WELLER
SOLDER TIP PT -H7
SOLDERING
IRON
SOLDER WICK
4822 321 40042
e.g. A PAIR OF TWEEZERS
HEATING
SOLDERING
IRON
SOLDER WICK
- 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 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
C).
o
- The chip, once removed, must never be reused.
Back
Repair Tips
VACUUM PISTON
4822 395 10159
A
HEATING
B
C
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
Fig. 2B).
Fig. 2
MOUNTING
e.g. A PAIR OF TWEEZERS
SOLDER
0.5 - 0.8 mm
SOLDERING
IRON
SOLDERING TIME
< 3 sec/side
PRESURE
2. Caution when attaching SMDs
- 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).
o
- 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
Fig. 3 Examples
RIGHT
SOLDERING
IRON
150B LCD
9
Go to cover page
A
PRESURE
SOLDER
B
0.5 - 0.8 mm
SOLDERING
IRON
(see Fig. 3).
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