PCB has a wide range of applications, almost all electronic equipment has to use PCB as the carrier. Therefore, there are many kinds of PCBs, different standards have different classification method. Such as according to the number of layers can be divided into double-sided printed board, multi-layer printed board, according to the properties of base material can be divided into rigid printed boards, flexible printed boards, rigid-flex printed boards, can also be divided into high-frequency microwave printed boards, HDI printed boards, blind buried hole printed boards, embedded components printed boards, etc according to the scope of application or structural particularity.