What is back drilling or controlled depth drilling in PCB?
PCB Back drilling is one of the special controlled depth drilling (NPTH) in the loop of PCB manufacturing process. Normally, there will be various challenges in engineering and production when it comes to PCB design and printed circuit board manufacturing and one of them is how to ensure high performance of retaining signal integrity.
When the electric PCB board transmits a signal, the signal quality received will be subjected to distortion from signal noise, crosstalk effect, and other undesired effects.
Thus, necessary incorporating design and manufacturing practices must be involved in to limit such effects and increases signal integrity. Via holes stubs often plays an important role to contribute to a decrease in signal integrity which can be effectively resolved through the use of via holes drilled by the back drilling process.
Back drilling (or called Controlled Depth Drilling (CDD)) is a technique calling which is used to remove the partial unused copper barrel from a through-plated-hole (via) in a electronic PCB board.
As these type of holes are back drilled to a certain-controlled depth, so this type of drilling process is also called PCB controlled depth drilling. In the back drilling process: the controlled depth tolerance is a critical parameter to limit the drilling’s depth, to make sure that the drilling not to hurt the useful copper which should be used as the conductive purpose to other layers.
So the back drilling technology can’t remove the via stub completely but necessarily keep useful cooper barrel as it is.Usually, it will residue a little (stub length smaller than 10mil).