With the development of electronic products in the direction of "light, thin, short, and small", PCBs have also developed to high density and high difficulty. Therefore, a large number of SMT and BGA PCBs have appeared, and customers require plugging when mounting components, mainly including Five functions:

　　(1) Prevent the tin from passing through the via hole to the component surface and cause a short circuit when the PCB is wave soldered; especially when we put the via on the BGA pad, we should first make the plug hole and then gold-plated, which is convenient for BGA welding.

　　(2) Avoid flux residue in the via;

　　(3) After the surface mounting and component assembly of the electronics factory are completed, the PCB must be vacuumed on the testing machine to form a negative pressure to complete:

　　(four) to prevent surface solder paste from flowing into the hole, causing false soldering, affecting placement;

　　(5) Prevent the solder balls from popping up during wave soldering, causing short circuits.