Filling Pastes in PCB Production - Fields of Application, Possibilities and Limitations

摘要

In the past the use of filling pastes in PCB production was largely limited to via hole fillers. These materials with a solids content of 100% are still successfully employed today to close via holes and thus ensure their proper sealing for vacuum adaptation during incircuit testing. Furthermore, they are used to avoid the deposition of flux residues that may create critical microclimates in the holes and/or under components. However, there is only limited use for these products in newer fields of pcb manufacturing. The latest filling materials (also referred to as plugging pastes) are largely used in Sequential Build-Up technology. Due to their specific properties, these materials enable the manufacturing of buried and blind via holes. Thick film fillers are of growing importance in case of extremely high copper build-up (also termed 400 um technology) in order to allow a leveling of the traces before a solder mask can be applied. All of the discussed materials belong to the electrically non-conductive type.