Soil Degradation of Sustainable PCB Substrates in Natural and Controlled Environments

This paper compares natural and controlled soil composting, in which the degradation of flax-fiber reinforced, flame-retarded polylactic acid (PLA) composite printed circuit board (PCB) samples are monitored. We aim to investigate the structural alterations that occur over a prolonged degradation process of these biodegradable laminates, utilized as environmentally friendly substitutes for PCB substrates. The experiment involves the degradation of functional blinker circuits with surface-mounted components and blank substrate boards without a conductive copper layer. During the long-term storage, we registered the composition of the surface with Fourier-transform infrared spectroscopy (FTIR) and inspected the changes in structure with scanning electron microscopy (SEM). Compared to traditional epoxy-based (FR4) references, significant changes (at both microscopic and visible levels) and the susceptibility to natural organisms can be observed, key elements in developing a greener and more sustainable approach for future PCB designs. After 40 weeks, the FTIR analysis showed the dominant presence of PLA in the naturally degraded samples. Cellulose, which acts as a reinforcement component, could be seen at specific locations within the cracks. The SEM study revealed contaminations and microbiological remnants on the boards’ surface, along with a growing number of cracks and slight PLA deterioration. The FTIR and SEM results also highlighted the efficiency of the controlled degradation, as a significant loss of resin in the composite started after 6 weeks.