Via hole plug in during PCB and SMT process, PCB and SMT process
Via hole plug in during PCB and SMT process

Via hole makes the connection of the lines between each other. The development of the electronics industry also promotes the development of PCBs. It also places higher demands on the manufacturing process and surface mount technology of printed circuit boards. Via hole plugging process is now common is PCB process, and the following requirements should be met:
1. There is copper in via hole, and solder resist be plugged, but not a must.
2. There must be tin in via hole, which has a certain thickness requirement (4 micrometers). There must be no solder resist entering the hole, which will resulting in solder beading in via hole;
3. Via hole must have solder mask plugged, which is opaque, and must not have solder beading in via hole, there is flat requirements of via hole on PCB surface.
With the development of electronic products in the direction of “light, thin, short and small”, PCBs are also developing towards high density and high difficulty. Therefore, a large number of BGA PCBs are bringing into being, and customers require plugging holes when manufacturing PCB.
There are five reasons of plugging via holes.
1. Prevent short in circuit. During reflow soldering process, If solder paste flow down to other side of PCB, will easily cause short, especially when we place via hole on the BGA pad, we must first make the hole plugged and then gold-plated to facilitate the BGA soldering.
2. Avoid flux remaining in the via hole.
3. During the surface mounting in the PCB assembly factory, PCB is picked up by vacuum grip machine, need to form a negative pressure to PCB surface.
4. Prevent the solder paste from flowing into via hole to cause inveracious soldering, which affects the soldering quality, bring connecting problems.
5. Prevent the solder beading from popping out during wave soldering, causing short in circuit.