Ericsson MGM 450, Руководство по обслуживанию

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COMPONENT REPLACEMENT
SURFACE MOUNT COMPONENTS
Surface mount components should always be replaced using a temperature controlled soldering system. The
soldering tools may be either a temperature controlled soldering iron or a temperature controlled hot-air soldering
station. A hot-air system is recommended for the removal of components on the multi-layered boards used in the
UHF synthesized mobile radio. With either soldering system, a temperature of 700
°
F (371
°
C) should be maintained.
The following procedures outline the removal and replacement of surface mount components. If a hot-air soldering
system is employed, see the manufacture’s operating instructions for detailed information on the use of your system.
•
CAUTION: Avoid applying heat to the body of any surface mount component using standard soldering methods.
Heat should be applied only to the metallized terminals of the components. Hot-air systems do not damage the
components since the heat is quickly and evenly distributed to the external surface of the component.
•
CAUTION: The CMOS Integrated Circuit devices used in this equipment can be destroyed by static discharges.
Before handling one of these devices, service technicians should discharge themselves by touching the case of a
bench test instrument that has a 3-prong power cord connected to an outlet with an known good earth ground.
When soldering or desoldering a CMOS device, the soldering equipment should have a known good earth ground.
SURFACE MOUNT REMOVAL
1. Grip the component with tweezers or small needle nose pliers.
2. Alternately heat the metallized terminal ends of the surface mount component with the soldering iron. If a
hot-air system is used, direct the heat to the terminals of the component. Use extreme care with the
soldering equipment to prevent damage to the printed circuit board (PCB) and the surrounding components.
3. When the solder on all terminals is liquefied, gently remove the component. Excessive force may cause the
PCB pads to separate from the board if all solder is not completely liquefied.
4. It may be necessary to remove excess solder using a vacuum de-soldering tool or Solder wick. Again, use
great care when de-soldering on the printed circuit boards. it may also be necessary to remove the epoxy
adhesive that was under the surface mount component and any flux on the printed circuit board.
SURFACE MOUNT COMPONENT REPLACEMENT
1. "Tin" one terminal end of the new component and the corresponding pad of the PCB. Use as little solder as
possible.
2. Place the component on the PCB pads, observing proper orientation for capacitors, diodes, transistors, etc.
3. Simultaneously touch the "tinned" terminal end and the "tinned" pad with the soldering iron. Slightly press
the component down on the board as the solder liquefies. Solder all terminals, allowing the component time
to cool between each application of heat. Do not apply heat for an excessive length of time and do not use
excessive solder. With a hot-air system, apply hot air until all "tinned" areas are melted and the component
is seated in place. It may be necessary to slightly press the component down on the board. Touch-up the
soldered connections with a standard soldering iron if needed. do not use excessive solder.
4. Allow the component and the board to cool and then remove all flux from the area using alcohol or another
approved flux remover.
MONOGRAM SERIES LBI-38865
COMPONENT REPLACEMENT
Page-29-
Nov. 94