Motorola CP185 Basic Service Manual page 78

C-2
Rigid Circuit Boards
This family of radios uses bonded, multi-layer, printed circuit boards. Since the inner layers are not
accessible, some special considerations are required when soldering and unsoldering components.
The printed-through holes may interconnect multiple layers of the printed circuit. Therefore, exercise
care to avoid pulling the plated circuit out of the hole.
When soldering near the connector pins:
• Avoid accidentally getting solder in the connector.
• Be careful not to form solder bridges between the connector pins.
• Examine your work closely for shorts due to solder bridges.
Chip Components
Use the RLN4062 Hot-Air Repair Station for chip component replacement. Adjust the temperature
control to 390 °C (735 °F), and adjust the airflow to a minimum setting. Airflow can vary due to
component density.
• To remove a chip component:
1. Use a hot-air hand piece and position the nozzle of the hand piece approximately 0.3 cm
(1/8") above the component to be removed.
2. Begin applying the hot air. Once the solder reflows, remove the component using a pair
of tweezers.
3. Using a solder wick and a soldering iron or a power desoldering station, remove the
excess solder from the pads.
• To replace a chip component using a soldering iron:
1. Select the appropriate micro-tipped soldering iron and apply fresh solder to one of the
solder pads.
2. Using a pair of tweezers, position the new chip component in place while heating the
fresh solder.
3. Once solder wicks onto the new component, remove the heat from the solder.
4. Heat the remaining pad with the soldering iron and apply solder until it wicks to the
component. If necessary, touch up the first side. All solder joints should be smooth and
shiny.
• To replace a chip component using hot air:
1. Use the hot-air hand piece and reflow the solder on the solder pads to smooth it.
2. Apply a drop of solder paste flux to each pad.
3. Using a pair of tweezers, position the new component in place.
4. Position the hot-air hand piece approximately 0.3 cm (1/8") above the component and
begin applying heat.
5. Once the solder wicks to the component, remove the heat and inspect the repair. All
joints should be smooth and shiny.
Repair Procedures and Techniques – General