B Rework (electronics) Process Reflowing and
Reflowing and reballing
Reballing involves dismantling, heating the chip until it can be removed from the board, typically with a hot-air gun and vacuum pickup tool, removing the device, removing solder remaining on the device and board, putting new solder balls in place, replacing the original device if there was a poor connection, or using a new one, and heating the device or board to solder it in place. The new balls can be placed via several methods, including:
Using a stencil for both the balls and the solder paste or flux,
Using a BGA "preform" with embedded balls corresponding to the device pattern, or
Using semiautomated or fully automated machinery.
For the PS3 and Xbox mentioned above, the time is about 120 minutes if all goes well.
Chips are at risk of being damaged by the repeated heating and cooling of reballing, and manufacturers' warranties sometimes do not cover this case. Removing solder with solder wick subjects devices to thermal stress fewer times than using a flowing solder bath. In a test twenty devices were reballed, some several times. Two failed to function, but were restored to full functionality after reballing again. One was subjected to 17 thermal cycles without failing.