When it comes to printed circuit board manufacturing, there are a variety of PCB via process requirements to consider. Each has their own pros, cons, and cost adders so knowing these requirements can aid you when designing your circuit boards. In this post we will discuss the differences for why you would either fill or plug a circuit board via.
Non-planar filling (without over-plating) prevents solder from migrating away from a nearby surface mount pad and down through the via during the PCB assembly process. It also helps to form a vacuum for assembly and for electrical testing.
Partially filling the barrel compensates for an LPI solder mask's inability to form a true 100% "tent" across the via, as dry film masks were able to do in the past.
Printed Circuit Board Surface Mount Pad After Via Pad Process
Plugging (with planarization and over-plating) is alternate option. If vias must be drilled through component mounting pads on a high density PCB, the plugs can be drawn down to completely fill the vias. The surface is then planarized and plated over, so that the pads can be used for soldering.
The over-plating option adds cost but some of that cost can be recovered through the use of smaller circuit board footprints and reduced layer count.