Problems of PCB Microvias Filling by Conductive Paste

In the paper there were analyzed the using polymer-base materials for the through holes and the blind holes filling in PCBs. Such processes seem to be easy and can be used instead of electrochemical plating process. The perform investigations show that these processes are not so simple. To understand more problems connected with microvias filling, the influence of adhesive rheology and printing parameters for the quality of filling small diameter through hole and small diameter blind vias were investigated. The performed analyze was supplemented by electrical measurements as well as observation of microvia cross sections. The FR-4 laminate test samples with through holes diameters: 0.3; 0.5 and 0.8 mm as well as blind holes diameters 0.15, 0.3 and 0.45 mm were used in experiments. The average single fill resistance in the range 50 mΩ and below was measured. Obtained adhesive fill resistance is stable after dump heat and thermal shock tests.