Service Manual Part 1
8.
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(a) Cracked SMD
Most often occurs with capacitors, caused by:
• Thermal shock: if the SMD is heated too rapidly either it will crack or internal
seals will be lost, resulting in premature failure.
• In-service temperature changes that cause invisible micro-cracks. These start
at or just under the end termination and will spread throughout the device
over a long period of time.
(b) Solder Joint Failure
• Stress causing flexing of the PCB leads to a cracked joint.
• Excessive or too little solder results in a poor quality joint.
• Various soldering process defects such as solder balling, device misalignment,
solder bridging and glue defects.
(c) Static Electricity Damage
If static electricity damage is suspected, remove and replace the component.
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Whenever components are removed from or fitted to the PCB, care must be taken to
avoid damage to the track. The two satisfactory methods of removing components from
PTH PCBs are detailed below.
8"88 $
Use a desoldering station, e.g. Philips SBC 314 or Pace MBT-100E for this method.
Place the tip over the lead and, as the solder starts to melt, move the tip with a cir-
cular motion.
Start the suction and continue the movement until 3 or 4 circles have been com-
pleted.
Remove the tip while continuing suction to ensure that all solder is removed from
the joint, then stop the suction.
Before pulling the lead out, ensure it is not stuck to the plating. If the lead is still
not free, resolder the joint and try again.
The desoldering iron does not usually have enough heat to desolder leads from
the ground plane. Additional heat may be applied by holding a soldering iron on
the tip of the desoldering iron (this may require a helper).