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Outline
This procedure is used to remove BGA devices that have been underfilled with non-reworkable epoxy underfill.
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Tools and Materials ▼
Additional Items and Supplies ▼
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Procedure
Procedure
- Enclose the circuit board assembly in a static barrier bag. Cut an opening in the bag to expose the underfilled device to be removed, and seal the edges to the circuit board with high-temperature tape.
- Secure the circuit board assembly with appropriate tooling and fixtures to the base of the milling machine. Set up a microscope to observe the milling operation.
Caution: Check to ensure the circuit board is rigidly secured in place and parallel to the milling machine base. Proper fixturing to hold and support the circuit board assembly is critical. - Install the appropriate end mill into the chuck of the milling machine and set the speed as required.
- Set up a vacuum system close to the milling area to remove dust and debris during the milling operation.
- Begin machining off the BGA device body, removing approximately .010 inches per pass. Repeat the milling process removing .010 inch thick layers until the entire body of the device has been machined away and the underfill epoxy is exposed.
- Begin machining off the underfill epoxy, removing .002 - .003 inch thick layers. Repeat the milling process removing .002 - .003 inch per pass until there is approximately .010 inch thick layer of underfill remaining on the circuit board surface. Vacuum all debris.
- Remove the circuit board assembly from the milling machine.
- Use Solder Braid and wick the solder that remains in each underfill pocket, exposing each of the pads on the circuit board surface.
- Re-install the circuit board assembly to the base of the milling machine.
- Continue machining the remaining underfill removing .001 inch per pass until there is approximately .003 - .005 inch thick layer of underfill remaining.
Caution: Exercise care to avoid machining through the underfill damaging the solder mask, pads, or surface traces. - Remove the board from the static bag and clean the area and circuit board as needed.
