A Green Conformable Thermoformed Printed Circuit Board Sourced from Renewable Materials

Printed Circuit Boards (PCBs) physically support and connect electronic components to implement complex circuits. The most widespread insulating substrate that also acts as a mechanical support in PCBs is commercially known as FR4 and is a glass fiber-reinforced epoxy resin laminate. FR4 has exceptional dielectric, mechanical, and thermal properties. However, it was designed without considering sustainability and end-of-life aspects, heavily contributing to electronic waste accumulation in the environment. Thus, greener alternatives are needed that can be reprocessed, reused, or biodegraded/composted at the end of their function.<br/>This work introduces diverse PCB substrates based on biobased and/or biodegradable polymers and fibers, a sustainable alternative to the conventional FR4. The substrates have been developed by compression molding, a process compatible with the polymer industry. We demonstrate that conductive silver ink can be additively printed on the substrate's surfaces, as their morphology and wettability are similar to those of FR4. The PCBs have tunable mechanical properties depending on the polymer-fiber combination, ranging from Young moduli of tens of MPa to GPa, and are thus flexible or rigid. Furthermore, they can be thermoformed to curved surfaces at low temperatures while preserving the conductivity of the silver tracks. The green substrates have a dielectric constant comparable to the standard FR4, while they are suitable for micro-drilling, a fundamental process for integrating electronic components into the PCB. The substrate's biodegradability is tested both in seawater and in soil. We implemented a proof-of-principle circuit to control the blinking of LEDs on top of the PCB, comprising resistors, capacitors, LEDs, and a dual in-line package circuit timer. The developed PCB substrate represents a sustainable alternative to standard FR4 and could reduce the overwhelming load of electronic waste in landfills.