Photopatternable, Performant, Degradable Polyimides for Reprocessible Multilayered Electronic Circuits

The growing accumulation of electronic waste (e-waste) presents a significant environmental challenge due to the non-degradable nature and limited recyclability of conventional polyimide (PI)-based substrates. We report the design and synthesis of a family of photopatternable, degradable polyimide network substrates that maintains high mechanical and electronic performance for reprocessible flex electronic circuitry. By incorporating degradable ester linkages within diallyl bisimide monomers and thiol crosslinkers, the substrate can be depolymerized under mild conditions for reprocessing without damaging the electronic components. Like other polyimide materials, these material exhibit desirable thermal properties (conductivity, K = 0.37–0.54 W m−1 K−1; degradation temperature, Td > 300 °C), mechanical properties (Young's modulus, ∼50 MPa; ultimate elongation, dL/L0 > 5%), and stable dielectric properties (dielectric constant, Dk = 2.81–3.05; dielectric loss, Df < 0.024) suitable for flexible electronic applications. Furthermore, the photopatternability can be leveraged for multilayered circuit manufacture. Our resin possesses a low viscosity for deposition at modest temperatures (< 80C), low shrinkage, and can survive solder reflow processes. By ulitilizing conventional photomasks, we selectively photopolymerize our PI in desired regions for build-up and redistribution layers. This additive approach yields the necessary "via" directly; we can simply remove the uncured and backfill the "via" with a conductor. The next layer's traces and components can then be built conventionally while simultaneously achieving the desired insulation and conductivity with the previous layer. This workflow is repeatable and infinite for an arbitrary number of layers of flexible circuitry. Our proposed manufacturing approach significantly reduces the complexity of building multilayered PI based circuits.