Back drilling is a technique used to remove via stubs from the inner layers of a multilayer PCB. Via stubs are non-functional portions of plated through-hole or via barrels which can cause unwanted reflections, leading to signal distortion and reduced performance. By eliminating via stubs, back drilling ensures consistent impedance alignment throughout the signal path, minimizing signal reflections and ultimately improving signal quality. If your design contains high-speed communication systems or sensitive analog circuits, back drilling is a good technique to meet your performance requirements.