Motorola HT-1000 Service Manual page 70

Shields
Removing and Replacing the
Shields:
RF PA (U105)
48
Once the part is off, turn off the heat, grab the part with a pair of
tweezers, and turn off the vacuum pump. Prepare the circuit board for
the new component by applying solder paste flux to the solder pads.
Position the circuit board under the heat-focus head, lower the head
to approximately 1/8"-1/4" (0.3cm-0.6cm) above the board, and turn
on the heat. When the solder left behind on the pads reflows, turn off
the heat and raise the heat-focus head. Remove the circuit board from
the holder and inspect the pads to ensure that the solder has flattened
out and that there are no solder shorts. Clean the area with alcohol
and a small brush.
Once the preparation is complete, place the circuit board back in the
circuit board holder. Add solder paste flux to the solder pads and place
the new component on the circuit board. Position the heat-focus head
over the component and lower it to approximately 1/8"-1/4" (0.3cm-
0.6cm) above the carrier. Turn on the heater and wait for the
component to reflow.
Once the component 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.
will be done with the R-1319, using the same procedure used to
remove and replace TSOP and PBGA components.
Place the circuit board in the circuit board holder. Select the proper
heat focus head and attach it to the heater chimney. Add solder paste
flux around the base of the shield. Position the shield under the heat-
focus head. Lower the vacuum tip and attach it to the shield by
turning on the vacuum pump. Lower the focus head until it is
approximately 1/8"-1/4" (0.3cm-0.6cm) above the shield. Turn on the
heater and wait until the shield lifts off the circuit board. Once the
shield is off, turn off the heat, grab the part with a pair of tweezers, and
turn off the vacuum pump. Remove the circuit board from the circuit
board holder.
To replace the shield, add solder to the shield if necessary, using a
micro-tipped soldering iron. Next, rub the soldering iron tip along the
edge of the shield to smooth out any excess solder. Use solder wick and
a soldering iron to remove excess solder from the solder pads on the
circuit board. Place the circuit board back in the circuit board holder.
Place the shield on the circuit board using a pair of tweezers. Position
the heat-focus head over the shield and lower it to approximately 1/
8"-1/4" (0.3cm-0.6cm) above the shield. Turn on the heater and wait
for the solder to reflow.
Once complete, turn off the heat, 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.
The procedure for removing and replacing the RF PA is very similar to
the procedure for removing and replacing an PBGA or a TSOP
component. But because the device is large, extra heating time is
required to flow the pads. And as a result, neighboring components
(especially those on the opposite side of the circuit board) will heat,