Cover-layering a Porous Polyimide Flexible Print Circuit with a Porous Polyimide Layer

Porous polyimide films are promising insulators for next generation electronic devices. Recently, we had developed a high-intensity UV exposure apparatus under a high-pressure CO2 gas atmosphere for the production of porous polyimide films. In this study, the cover-layering process of a porous polyimide layer on two different types of flexible print circuits (FPCs) with insulation materials made of solid polyimide and porous polyimide was examined. Although a portion of the pores above and below the copper line of the FPC collapsed, a conformal porous polyimide layer could be formed on the FPC. Through-holes were formed on the porous polyimide film by a laser ablation technique. The surface of through-holes was electro-plated in a copper-plating solution bath. A portion of the pores on the film were filled with copper as the pores were inter-connected and the plating solution penetrated the pores. The results suggest that the pores should be isolated and firm for a cover-layering process with porous polyimide films for next-generation FPCs.