As the centering core in electronics products, PCBs (Printed Circuit Boards) are responsible for carrying all the functions products have to implement in the whole system. The combination of bare PCBs and components leads electronic products to be smaller in size and weight and to better perform in electrical connection. Since the advent of assembly technology to logically and solidly stick components to bare boards, THT (Through-Hole Technology) assembly has been widely applied to make electronic components with leads directly going through holes on boards and make the other end of leads soldered on board back.