Electronic circuits behave very differently at high frequencies. This is mainly due to a change in the behavior of the passive components (resistors, inductors, and capacitors).
BGA stands for Ball Grid Array and they use solder balls arranged in the form of an array to make an electrical connection.
The IC substrate acts as a bridge that connects the microchip and PCB by making electrical connections.
IC substrate PCB is simply the base material of the IC package, providing connections between the PCB and the IC package on the printed circuit board.
