Soil Degradation of Sustainable PLA/Flax Substrates and Printed Circuit Board Assemblies

In this study, flax-fiber reinforced, flame-retarded polylactic acid (PLA) composite printed circuit board substrate samples were prepared to investigate the long-term effects of soil degradation on stability and structural changes. After a moderate heat stressing in reflow environment (170°C, 300 s), 16-16 pieces of substrates and blinking circuit boards were placed to a composting bin. The ongoing examinations started nine months ago. The weight changes of samples are registered regularly, along with control parameters of soil, namely the moisture content (%), conductivity (µS/cm) and temperature (°C) values with a sensor node. During the evaluation, weather conditions were also considered (daily and weekly values of average temperatures and rainfall amount). As the weather conditions influenced the moisture content and the temperature of the soil, moisture absorption and soil deposition expressed in a divided weight gain tendency, referring to the different seasons during the 31-week period.