Biodegradable PCBs with PLA/Flax Substrate: FTIR and SEM Analysis of Soil Degradation

Recently, polylactic acid and flax-textile-based, reinforced, flame retarded composite was introduced, which is promising in terms of PCB applications as a substitute for the dielectric. This paper extends our knowledge with analytical investigations on the substrates, specifically degradation in natural environments. After preparing bare laminate samples and assembled, one-sided demonstrational circuits with traditional surface mounting technology, the boards were introduced to natural composting in a composting bin with outdoor ambiance and FR4-based reference samples. The boards were kept in the soil for 43 weeks. In selected time points, the samples were subjected to the following analytical investigations: Fourier-transform infrared spectroscopy (FTIR) to reveal the composition of the surface structure before and during degradation; scanning electron microscopy (SEM) to analyze the topography and the structure before and during degradation. As FTIR showed, PLA is still dominant on the surface of the boards after 37 weeks of degradation. The analysis also revealed that after 40 weeks of soil degradation, the cellulose (from the reinforcement textile) was exposed to the surface. The SEM analysis showed cracks and minor degradation of the PLA on the surface of the boards during the weeks, revealing contaminations and microbiological remains. sEM also showed that PLA is heavily present on the reference surface and the degraded samples. Microbe specimens were also investigated on the degradable samples, while the reference boards contained no similar findings. © 2024 IEEE.