Resin plug hole PCB is more acid and alkali resistant than green oil PCB. PCB uses resin plug hole. This process is often due to BGA parts, because traditional BGA may make VIA between PAD and PAD to the back of the wiring, but if the BGA is too dense When VIA can't go out, you can drill holes directly from the PAD to make vias to other layers to route the wires, and then fill the holes with resin to fill and plate the copper into PAD, which is commonly known as the VIP process (via in pad). Making vias on the PAD without using resin plug holes will easily cause leakage of tin, leading to short circuits on the back and empty soldering on the front.