Definition

Via plugging fills via holes with non-conductive epoxy paste, providing a barrier against solder wicking and creating a more planar surface. Plugging is required for via-in-pad designs where solder could wick into open vias during reflow, starving the joint. Plugged vias can be capped (plated over) for complete planarization. Via plugging adds cost but is essential for fine-pitch BGA assemblies. The plug material must withstand reflow temperatures without outgassing or failure.