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Repair tips 104S CM23 GSIII 29
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0. Warning solder the component on one side. Ensure that the component is
positioned correctly on the solder lands (see Fig. 8.2A).
All ICs and many other semi-conductors are susceptible to - Next complete the soldering of the terminals of the component (see
electrostatic discharges (ESD). Careless handling during repair can Fiq. 8.2B).
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 ! 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.
- Avoid using storage places that are sensitive to oxidation such as
SOLDER
places with sulphur or chlorine gas, direct sunlight, high 0.5 - 0.8 mm
temperatures or a high degree of humidity. The capacitance or SOLDERING
PRESURE
resistance value of the SMDs may be affected by this. IRON
- 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 SOLDERING TIME SOLDER
circuit board materials expand and contract at different rates when < 3 sec/side 0.5 - 0.8 mm B
PRESURE
heated or cooled and the components and/or solder connections SOLDERING
may be damaged due to the stress. Never rub or scrape chip IRON
components as this may cause the value of the component to
change. Similarly, do not slide the circuit board across any 2. Caution when attaching SMDs
surface. Fig. 8.2
- When soldering the SMD terminals, do not touch them directly with
1.2 Removal of SMDs the soldering iron. The soldering should be done as quickly as
- Heat the solder (for 2-3 seconds) at each terminal of the chip. By possible, care must be taken to avoid damage to the terminals of
means of litz wire and a slight horizontal force, small components the SMDs themselves.
can be removed with the soldering iron. They can also be - Keep the SMD's body in contact with the printed board when
removed with a solder sucker (see Fig. 8.1A) soldering.
- The soldering iron to be used (approx. 30 W ) should preferably be
equipped with a thermal control (soldering temperature: 225 to
DISMOUNTING
250 oC).
VACUUM PISTON - Soldering should not be done outside the solder land.
SOLDERING 4822 395 10159
IRON - Soldering flux (of rosin) may be used, but should not be acidic.
- After soldering, let the SMD cool down gradually at room
e.g. WELLER
SOLDER TIP PT -H7 temperature.
A
- The quantity of solder must be proportional to the size of the solder
SOLDERING
land. If the quantity is too great, the SMD might crack or the solder
IRON lands might be torn loose from the printed board (see Fig. 8.3).
SOLDER WICK
4822 321 40042
e.g. A PAIR OF TWEEZERS
HEATING HEATING
B
EXAMPLES
SOLDERING
IRON
C
SOLDER WICK
RIGHT
Fig. 8.1
- 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. 8.1 B).
- Remove the excess solder on the solder lands by means of litz wire
or a solder sucker (see Fig. 8.1C).
1.3 Caution on removal SOLDERING
IRON
- 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 oC). Fig. 8.3
- The chip, once removed, must never be reused.
1.4 Attachment of SMDs
- Locate the SMD on the solder lands by means of tweezers and
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