Why these boards are called sandwich boards
Multiple board layers are joined through a dense field of interposer connections. Faults between those layers can require separation before the hidden connection area can be inspected or rebuilt.
Reballing recreates the joining pattern
After preparation, solder is formed into a consistent array across the layer. Alignment, heat control and surface condition all matter before the layers can be joined again.
Technique footage is not a diagnosis
The same operation may appear in repairs involving impact, intermittent communication, signal or other layer-related faults. Without the original measurements, this footage cannot establish which symptom led to the work.
Functional testing remains a separate requirement
A clean ball pattern is an intermediate workmanship result. Power, communications and the original reported functions still need to be tested after the board is reassembled.
