CHARACTERISTICS OF BLIND HOLE IN BUILD-UP LAYER MADE OF ARAMID REINFORCED PLASTICS

摘要

Printed wiring boards have been required for semiconductor mounting used in Chip Size / Scale Packages (CSPs). Aramid fiber reinforced plastic (AFRP) is considered suitable material for the build-up layers of those PWBs, because the AFPR has a low coefficient of linear thermal expansion in the x-y plane. In the present report, attempts were made to compare the characteristics of blind holes drilled with a laser in a build-up layer made of AFRP (a new material) and GFRP (FR-4 type material). First, the efficiency of drilling in the layer was discussed. Second, we investigated the influence of the taper angle and the surface roughness after drilling on the fluidity of the plating liquid. Finally, the thermal stresses in the copper plating of blind via hole were analyzed by the finite elemental method (F.E.M.) in order to estimate the reliability for the circuit connection. As a result, the drilling in the AFRP layer can be done with twice the efficiency of that in the GFRP layer. The via hole in the AFRP shows good copper plating due to the smooth surface roughness of the wall itself. On the other hand, it is necessary to decrease the thickness of the layer in order to decrease the thermal stress in the copper plating.