Minimum mill tool diameter is 0.8mm,the standard diameter is 2.0mm,the special diameter is >=0.8mm<2.0mm
The inner and outer contour of the board milled as per customers specification.
The outer of contour could be 90°or round according to customers specification but the inner corner of the profile has at least the radius of the milling cutter
Generally, the corner of the rectangle are round, in order to maintain a precise rectangular section, the corresponding milled part should also be drilled at the corners
Backdrill is the process of creating vias by removing the stub in multilayered printed wiring boards, to allow signals to flow from one layer of the board to another. It is a special craftsmanship of control depth drilling.
Reduce the use of blind and buried vias to reduce the difficulty of PCB fabrication
Improve signal integrity
Reduce interference of other signal
Reduce partial plate thickness