Statement: This post is only the personal view of the author and does not represent the opinions of ALLPCB.com.
You should not flex your boards. A cracked solder joint on a
rigid part is possible.
Looking for rigid parts with the along axis aligned across the
bow of the flex.
The flexing creates shear forces within the board, depending upon
your via count and size and amount of plating, you can easily
shear your vias and even tear them loose from the traces.
If you are looking at the different parts of the PCB, such as a
motherboard. Denote, where the 4.3 volts, 5 volts and other
voltages come in, these are known as rails on the motherboard,
as in power supply rails.
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