Plugging, Holefilling, Microvia Copper Filling or Via Hole Plugging refers to the filling of metallized through holes or metallized blind holes on the outer layers of the printed circuit board. There, a planar surface topography can be achieved even with highly complex circuit carriers, through which the process safety and reliability in the assembly process, no solder run-off, no air inclusions, can be significantly increased.
The result is fillet-and-capped vias . Components can be placed directly via these vias and the integration density increased. The advantages are a considerable gain in space for SBU setups (SBU: sequential build up) and fewer restrictions in the layout design of complex circuits.
The metallized holes are filled with a special plugging paste and then over-metallized. There are various technological options for introducing the paste into the borehole, each with its own specific advantages and disadvantages:
– roller coating process
– screen printing process
– stencil printing
– vertical vacuum filling
KSG opted for full-surface vertical vacuum filling due to the wide range of applications. This process makes it possible to fill not only through holes but also mechanically drilled or laser-drilled blind holes quickly, reliably and reproducibly and is thus available for many applications. Further advantages compared to conventional screen printing processes are the air bubble free filling of the holes, a high flexibility, a lower paste consumption as well as the filling of holes with a higher aspect ratio.