What is Via Plugging?

Via plugging is a process in which vias are completely filled with resin or closed with a solder mask. This technique is different from via tenting where resin/solder mask doesn’t fill the via hole but just provides a covering.

Via plugging is done as a preventive measure to secure the vias from the unwanted flow of solder material during the assembly/soldering process. During the soldering process, if a via is not plugged or tented, the solder can flow down the via from the pads and can create unnecessary solder joints.

Via plugging can be done using conductive or non-conductive materials. The conductively filled vias help to carry a large amount of current from one side of the PCB board to another. However, the main drawback of conductively filled vias is the difference in CTE (Coefficient of Thermal Expansion) between the conductive fill and surrounding laminate. During PCB operation, the conductive material will heat and expand at a faster rate than the surrounding laminate, which can cause a fracture between the via wall and associated contact pad.

The via holes filled with non-conductive materials will still function like normal vias. However, they will not be able to carry higher current loads like those filled with conductive materials.