Sustainable, flame-retarded and biodegradable printed circuit boards based on polylactic acid (PLA) with wool-fibre reinforcement: review of processing and manufacturing technologies

• Increasing demand for eco-friendly products has accelerated PLA's role as a sustainable option for future printed circuit board substrates. • Assess the mechanical, thermal, and electrical properties of PLA and provide a summary of its processing and manufacturing methods. • Compositions, reinforcement materials, and flame retardants for PLA are explored, highlighting their benefits and limitations. • Examination of assembling practices includes comparing component insertion and soldering methods for PLA-based applications. Among the increasing utilisation of biopolymers, polylactic acid (PLA) has gained significant attention as a biodegradable alternative to petroleum-based plastics in various applications, including electronics, packaging, and biomedical fields. Because of its enormous potential as a green and eco-friendly substitution for traditional printed circuit board (PCB) substrates, and its satisfactory reliability in many prototype applications, PLA reached the most important stage in the line of alternative materials for designing future-proof and sustainable electronic devices. Due to the growing demand for environmentally friendly products from both the industry and customers, innovative solutions' sustainability needs equal weight with their performance and dependability. This study focuses on creating a narrative and scoping review to investigate the typical properties of PLA. It summarises the processing and manufacturing techniques that convert PLA into printed circuit substrates. The paper explores the basic parameters and different compositions of PLA with reinforcement materials, focusing on a specific fibre addition, wool. As an added value, the manuscript presents the related eco-friendly flame-retardant solutions. The currently applied subtractive (e.g. compression and casting methods) and additive (e.g. inkjet printing, 3D printing) fabrication methods are investigated, pointing out the benefits and shortcomings through the foregoing research projects and the presented applications. The assembly practices of electronics on PLA are also investigated, and typical routines of component mounting and soldering methods are compared. The paper aims to cover the research gap in fibre-reinforced, sustainable, flame retarded PLA substrates for future green electronics.