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GTX LTR/Privacy Plus 800 MHz Mobile Service Manual
nent replacement. When using the 0180381B45 Repair
Station, select the TJ-65 mini-thermojet hand piece. On
either unit, adjust the temperature control to 700˚ F
(370˚ C), and adjust the airflow to a minimum setting.
Airflow can vary due to component density.
Chip Component Removal
To remove a chip component, select a hot-air hand
piece and position the nozzle of the hand piece approx-
imately 1/8" above the component to be removed.
Begin applying the hot air. Once the solder reflows,
remove the component using a pair of tweezers. Using
solder wick and a soldering iron or a power desolder-
ing station, remove the excess solder from the pads.
Chip Component Replacement
To replace a chip component using a soldering iron,
select the appropriate micro-tipped soldering iron and
apply fresh solder to one of the solder pads. Using a
pair of tweezers, position the new chip component in
place while heating the fresh solder. Once solder wicks
onto the new component, remove the heat from the sol-
der. 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, select the
hot-air hand piece and reflow the solder on the solder
pads to smooth it. Apply a drop of solder paste flux to
each pad. Using a pair of tweezers, position the new
component in place. Position the hot-air hand piece
approximately 1/8" above the component and begin
applying heat. Once the solder wicks to the compo-
nent, remove the heat and inspect the repair. All joints
should be smooth and shiny.
Over-Molded Pad-Array Carrier (OMPAC)
ASFIC U201 is an OMPAC. It must be kept in a sealed
bag with dessicant in the bag (in a "dry box" as sup-
plied by the Motorola Parts Department prior to use. If
the OMPAC is ambient for an unknown amount of
time or for more than 96 hours, then it must be baked
for at least eight hours at 260˚ F (185˚ C).
If neighboring OMPAC components are heated above
365˚ F (185˚ C), they will suffer die-bond delamination
and possible "popcorn" failure.
During all repair procedures, heating neighboring
components can be minimized by:
• Using upper heat only. using the correct size
heat-focus head, approximately the same size as
the carrier being replaced.
• Keeping the heat-focus head approximately 1/
8" (0.3cm) above the printed circuit board when
removing or replacing the device.
June, 2000
OMPAC Removal
To remove the OMPAC, select the R-1070A Air-Flow
Station and the appropriate heat- focus head (approxi-
mately the same size as the OMPAC. Attach the heat-
focus head to the chimney heater. Adjust the tempera-
ture control to approximately 415˚ F (215˚ C) 445˚ F
(230˚ C) maximum. Adjust the airflow slightly above
the minimum setting. Apply the solder paste flux
around the edge of the OMPAC. Place the circuit board
in the R-1070A's circuit board holder, and position the
OMPAC under the heat-focus head. Lower the vacuum
tip and attach it to the OMPAC by turning on the vac-
uum pump. Lower the heat-focus head until it is
approximately 1/8" (0.3cm) above the carrier. Turn on
the heater and wait until the OMPAC lifts off the circuit
board. Once the part is off, grab it with a pair of twee-
zers and turn off the vacuum pump. Remove the circuit
board from the R-1070A's circuit board holder.
OMPAC Replacement
To replace the OMPAC, the solder pads on the board
must first be cleaned of all solder to ensure alignment
of the new chip carrier. Prepare the sight by using sol-
der wick and a soldering iron to remove all solder from
the solder pads on the circuit board. If a power desol-
dering tool is available, it can be used instead of the sol-
der wick. Clean the solder pads with alcohol and a
small brush. Dry and inspect. Ensure that all solder is
removed.
Once the preparation is complete, place the circuit
board back in the R-1070A's circuit board holder. Add
solder paste flux in the trench of the flux block and
spread it using a one-inch putty knife. Flux the
OMPAC by placing it in the trench of the flux block.
Once the flux is applied, place the OMPAC on the cir-
cuit board, making certain that it is oriented correctly
on the board. Position the heat-focus head over the
OMPAC and lower it to approximately 1/8" (0.3cm)
over the carrier. Using the same heat and airflow set-
ting used to remove the OMPAC, turn on the heater
and wait for the carrier to reflow (heating and reflow
should take longer than 60 seconds).
Once the carrier reflows, raise the heat-focus head and
wait approximately one minute for the part to cool.
Remove the circuit board and inspect the repair. No
cleaning should be necessary.
Shields
Removing and replacing the shields will be done with
the R-1070A, using the same heat and airflow profile
used to remove and replace OMPAC components.
Shield Removal
Place the circuit board in the R-1070A's holder. Select
the proper heat focus head and attach it to the heater
6880905Z99-O
Basic Maintenance
Repair Procedures and Techniques
2-3
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Troubleshooting
