Biodegradable and Water-Soluble DEG1 Substrate for Printed Circuit Board Applications

This paper presents a novel substrate for sustainable microelectronics applications in printed circuit board (PCB) rigid substrate technology. DAT1 is a biodegradable, water-soluble, non-polymer insulating material that may alternatively replace current rigid PCB dielectric materials in selected applications. We present the process of preparing conductor tracks on the boards with thick-film technology and subtractive laser processing of laminated copper. We investigate the surface roughness, present peel-testing results, and basic assembling approaches (based on surface mounting) with low-temperature reflow soldering (LTS with SnBiAg-based alloy). We present water moisture tests with water solubility analysis. It was found that conductive patterns can be created on the surface using conventional copper layer and thick-film printing technologies. Components can be joined by conductive adhesive or low-temperature (SnBi) alloys, with profiles maximized at 150 °C. DAT1 and Cu foil structures can be laminated, forming a pre-preg basis. Laser etching of the substrate is achievable. The obtained peel force is currently 0.6-0.7 N/mm, below the accepted values based on Flame Retardant Class 4 technology, but in line with similar substrates. Surface roughness was recorded between 0.84 and 1,2 μm. The composition of the substrate surface did not change after the reflow heating. Moisture absorption resulted in ~15% after 75 hours. Water degradability was presented qualitatively after ~24 hours of degradation.