Safe Handling Of Cmos And Ldmos; General Repair Procedures And Techniques - Motorola PR860 Detailed Service Manual

3-2
NOTE: Always use a fresh supply of alcohol and a clean container to prevent contamination by
dissolved material (from previous usage).
3.4

Safe Handling of CMOS and LDMOS

Complementary metal-oxide semiconductor (CMOS) and lateral diffusion metal oxide semiconductor
(LDMOS) devices are used in this family of radios. Their characteristics make them susceptible to
damage by electrostatic or high voltage charges. Damage can be latent, resulting in failures
occurring weeks or months later. Therefore, special precautions must be taken to prevent device
damage during disassembly, troubleshooting, and repair.
Handling precautions are mandatory for the circuits and are especially important in low humidity
conditions. DO NOT attempt to disassemble the radio without first referring to the CMOS CAUTION
paragraph in the Disassembly and Reassembly section of the basic manual (See Chapter 3).
3.5

General Repair Procedures and Techniques

• Parts Replacement and Substitution
When damaged parts are replaced, identical parts should be used. If the identical replacement
component is not locally available, check the parts list for the proper Motorola part number and
order the component from the nearest Motorola Communications parts center listed in the "Piece
Parts" section of this manual (See Chapter 1).
• Rigid Circuit Boards
The 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, care should be exercised to avoid pulling the plated circuit out of the hole.
When soldering near the 20-pin and 40-pin connectors:
- Avoid accidentally getting solder in the connector.
- Be careful not to form solder bridges between the connector pins.
- Closely examine your work for shorts due to solder bridges.
• Flexible Circuits
The flexible circuits are made from a different material than the rigid boards and different
techniques must be used when soldering. Excessive prolonged heat on the flexible circuit can
damage the material. Avoid excessive heat and excessive bending.
For parts replacement, use the ST-1087 Temperature-Controlled Solder Station with a
600–700 degree tip, and use small diameter solder such as ST-633. The smaller size solder will
melt faster and require less heat to be applied to the circuit.
To replace a component on a flexible circuit:
1. Grasp the edge of the flexible circuit with seizers (hemostats) near the part to be removed.
2. Pull gently.
3. Apply the tip of the soldering iron to the component connections while pulling with the seizers.
Do not attempt to puddle out components. Prolonged application of heat may damage the
flexible circuit.
Maintenance: Safe Handling of CMOS and LDMOS