The keyboards in modern Macs are very simple devices with a horizontal grid, an almost vertical grid and a simple processor that detects when you push a button that changes the resistance at a grid intersection, and forwards a keycode to the computer.
When they stop working, they are un-repairable.
The field-replaceable assembly is the keyboard-battery-trackpad-topplate assembly.
leroydouglas supplied the only possible answer to your query as written -- readers are sorry you did not like the answer.