背钻多用于高多层板的钻孔加工，其目的是去除没有起到任何连接或信号传输作用的通孔段，
避免造成信号传输的反射、散射、延迟等；
由于其主要去除对象为孔壁电镀的铜层，因此对钻头的排屑性能有着极高的要求，
如果无法顺利排屑，就极易造成堵孔、孔偏等问题。
Back drilling is mostly used for drilling in high multi-layer boards.
Its purpose is to remove through hole sections that do not serve any connection or signal transmission function
Avoid causing reflection, scattering, delay, etc. in signal transmission;
As its main removal target is the copper layer electroplated on the hole wall,
it has extremely high requirements for the chip removal performance of the drill bit.
If the chips cannot be removed smoothly,it is very likely to cause problems such as hole blockage and hole deviation.