3D Printed Circuit Boards from Recycled Plastics: Conductive Pattern Properties

The aim of this work is to advance further the development of an environmentally friendly method of manufacturing printed circuit boards (PCBs) using recycled and recyclable 3D printable polymers as an insulating substrate and electrically conductive pastes for the conductive pattern. Previous iterations of this alternative process development were focused on the automatic dispensation of ink from the cartridge to create the conductive pattern. To reduce the time required for production, increase the accuracy of the process, and make it much more implementable in practice, screen printing was employed for the creation of a conductive pattern in this study. Two conductive pastes were used in this study: a silver-based paste and a copper-based paste. For the protection of the patterns against degradation, two different methods were tested: overprinting with another polymer layer by 3D printer and coating with an acrylic varnish. To test the functionality of surface treatments and their effect on the circuit’s reliability, samples were placed in a desiccator at $99 \%$ relative humidity. The results, however, showed that the effect of the tested surface finish is negligible, and the durability of the conductive patterns under a humid environment is given primarily by the paste itself. The silver-based paste showed no significant change after 125 days in the desiccator. On the contrary, complete degradation of the copper-based patterns occurred after only 6 hours in the desiccator. Despite being more environmentally friendly, the copper-based paste is not practically usable from this point of view without significantly more robust surface protection, such as plating. Therefore, the silver-based pastes will be utilized in further continuation of this project.