A two-layer high density printed circuit board and its reliability

The fabrication and reliability of a two-layer high density PCB test vehicle are reported in this paper. The test board consisted of two copper layers that were sequentially built up on one side of a FR4 substrate and interconnected through a photovia dielectric layer. Various test structures were fabricated for reliability testing. Thermal cycling, 85°C/85%RH ageing, and multiple reflow excursions were performed to test the reliability of electrical continuity and insulation. Peel strength was measured after fabrication as well as after 150°C annealing and reflow excursions. Initial results have revealed that photovias may be more reliable than conventional through vias.