Sustainable Electronics
hazardous wastewater, and dangerous microparticles of metal and glass. Furthermore, none of these methods allow the reusing of the PCB material in other PCBs, though in some cases the materials can be reused in other applications such as fibreglass insulation. The ultimate goal then would be to create a PCB with the appropriate mechanical, chemical and electrical properties which can be sustainably recycled.
One team at the University of Washington has been working to meet this challenge 8
by developing a possible
the extraction of raw materials, the volume of waste produced and the energy use associated with the production of new materials.
Unfortunately, things are not so simple. The drives to make electronics smaller and more resilient can be at odds with a push towards sustainability. Circuits are often made smaller by manufacturing components directly into PCBs which can make it harder to retrieve components and materials. Smaller components are harder to identify, remove and sort, and more resilient electronics are harder to break down and safely dispose of. PCBs are the industry standard for integrating electronics into all kinds of devices. As first invented by Paul Eisler and most notably described in his patent application US2441960 5
that PCBs be so resistant to a wide range of chemicals, it becomes difficult to deconstruct them at the end of a product’s life. Additionally, developing more sustainable alternatives to conventional PCB materials is hard simply because they must fulfil so many specifications. Conventional recycling methods focus on recovering only the metals from PCBs, with early patents relating to PCB recycling dating back to the 1990s. One patent described a method of cooling PCBs with liquid nitrogen to make them brittle before grinding them up 7
. Other methods
involve burning, dissolving in acid, or shredding the PCB, before using further processes to separate out the products, but each of these methods has associated environmental hazards such as toxic fumes,
, they can be mass
produced cheaply, and custom printed to almost any application. Therefore, learning to effectively recycle PCBs is a vital step on the road to sustainability.
PCBs are typically constructed from thermoset epoxies surrounding a glass- fibre weave for added stability. Despite its use in circuit boards first being patented as far back as the 1970s 6
, the most common
epoxy used is still the fire-retardant FR-4. Copper traces are then printed and/or etched onto the epoxy-glass-fibre core to create the circuit, and holes may be drilled for the attaching of components. Integrated components may also be added, such as by printing silicon-based semiconductors onto the PCB, and a coating is added to protect the metals and semiconductors. Such PCBs are designed to be extremely resilient to mechanical and chemical stresses. They are made, as the name suggests, resistant to fire, as well as water and various chemicals, and have specific electrical properties such as resistivity and dielectric constant. However, by requiring
www.cieonline.co.uk
replacement for FR-4 based PCBs. They have been developing PCBs made from a special type of organic polymers called ‘vitrimers’. Vitrimers are soluble in certain organic solvents which allows them to be partially or fully dissolved for various purposes. For instance, holes or bends in vitrimer PCBs can be more easily repaired by partially dissolving them. At the end of a product’s life, a vitrimer PCB can be fully dissolved to retrieve metal circuit traces and the core materials, even whole components. In testing, the research team was able to recover 98 per cent of the polymer, 100 per cent of the glass fibres and 91 per cent of the solvent. The developed PCBs were shown to have comparable mechanical and electrical properties to FR-4 PCBs. Vikram Iyer, one of the researchers, also told us that “there’s a whole host of vitrimer chemistries that could be used…to
enable applications that require different specs (higher temperatures, etc.)”. The applications could be huge, and the researchers hope that these circuit boards could become “a drop-in replacement for existing FR-4”.
A key focus of the team was developing soluble PCBs which can be manufactured in a similar way to existing PCBs. “By using the same equipment [as existing PCBs] it is both much easier for manufacturers to adopt and it allows anyone to start producing more sustainable PCBs. This also makes it more compelling for companies that seek to use sustainable PCBs in their products”, Iyer told us. Just as important as developing new technologies to confront the sustainability challenge is ensuring they can be properly implemented into supply chains. Without this it may never be possible to put these laboratory innovations to practical effect.
Reaching a true closed-loop recycling system for electronics also necessitates developing suitable recycling techniques for electronic components, such as resistors, capacitors and transistors. This arguably presents an even greater challenge because the diversity of materials used in different components is enormous. The reusing of complete components is also difficult because of the diversity of components and their often- tiny size. To properly reuse a component involves disassembling the circuit board without damaging it, identifying the component and then testing that they still function properly. As many components are mass produced cheaply, making it financially viable to reuse components will require a great deal of work. While there is a long way to go in improving the sustainability of the electronics sector, breakthroughs like the one made by the researchers at the University of Washington represent a crucial step. The role of patents in providing incentives for innovation and providing the knowledge required for improvements to existing designs will be vital in ushering in the next generation of electronics.
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References: 1
2 Application 201715743253A Smart Belt, published 2022
Global E-waste monitor 2024:
https://ewastemonitor.info/wp-content/uploads/2024/03/GEM_2024_18-03_web_page_per_page_web.pdf 3 Statistic from the Circular Electronics Partnership Roadmap:
https://cep2030.org/wp-content/uploads/2024/04/CEP-Roadmap-2.0.pdf 4 Data taken from
Patbase.com: Number of patent families published in each year containing “electric” AND “vehicle” in the title, abstract or claims. Manufacture of Elecric Circuit Components, published 1948
5 6 7
Application GB1293801A Printed Circuit Boards and Methods of Making Same, published 1972 K. O. Tiltmann "Recycling betrieblicher Abfalle", loose-leaf edition, July 1991, WEKA Fachverlag Kissingen 1990
8 Recyclable vitrimer-based printed circuit board for circular electronics, published 2024:
https://www.nature.com/articles/s41893-024-01333-7 Components in Electronics December/January 2025 41
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