e. Over-Molded Pad-Array Carrier (OMPAC)
During all repair procedures, heating neighbor-
ing 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”-1/4” (0.3cm-0.6cm) above the printed
circuit board when removing or replacing
the device.
(1) To remove an OMPAC, select the R-1319
Rework Station and the appropriate heat-
focus head (approximately the same size
as the OMPAC. Attach the heat-focus head
to the chimney heater. Adjust the tempera-
ture control to approximately 415 degrees F
(215 degrees C); 445 degrees F (230
degrees C) maximum. Apply the solder
paste flux around the edge of the OMPAC.
Place the circuit board in the 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
vacuum pump. Lower the heat-focus head
until it is approximately 1/8”-1/4” (0.3cm-
0.6cm) 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 tweezers and turn off the vac-
uum pump. Remove the circuit board from
the R-1070’s circuit board holder.
(2) To replace an OMPAC, the solder pads on
the board must first be cleaned of all solder
to ensure alignment of the new chip carrier.
Prepare the site by using solder wick and a
soldering iron to remove all solder from the
solder pads on the circuit board. If a power
desoldering tool is available, it can be used
instead of the solder 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 circuit board hold-
er. 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 circuit
board, making certain that it is oriented cor-
rectly on the board. Position the heat-focus
head over the OMPAC and lower it to
approximately 1/8”-1/4” (0.3cm-0.6cm) over
the carrier. Using the same heat setting
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).
Watch the OMPAC reflow
and note that when a proper reflow has
taken place, the OMPAC will drop (usually
one side, then the other). The end result is
that both sides have reflowed, and the
OMPAC is sitting parallel to the circuit
board.
Once the carrier reflows, raise the heat-
focus head and wait approximately one
minute for the part to cool. Remove the cir-
cuit board and inspect the repair. No
cleaning should be necessary.
26
If neighboring OMPAC components are
heated above 365 degrees F. (185 degrees
C.), they will suffer die-bond delamination and
possible “popcorn” failure.
All pad-array carriers in these radios, except
for the IF IC (U3), are OMPAC. Prior to use,
all OMPACs must be kept in the sealed bag
(with moisture-indicator card) as supplied by
the Motorola Parts Department. Once the
sealed bag is opened and/or the OMPAC
subjected to ambient humidity (for an
unknown amount of time or for more than 96
hours) then that OMPAC must be baked in
an oven for at least eight hours at 260
degrees F. (125 degrees C.)
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