BY ANTHONY KING
Electronic waste is fast accumulating in our environment, and printed circuits boards are major components. Now, researchers are exploring ways to make them more sustainable. Anthony King reports.
Printed circuit boards are essential parts of electronics. It is the typical hard bright green material you see inside any consumer electronics, from a TV to a desktop computer. Most PCBs are made of woven fibreglass cloth for mechanical strength and epoxy resin for binding and insulation, with a layer of copper foil chemically etched into conducting lines. They are strong, fire retardant and reliable.
Environmentally, however, electronic waste is a growing problem. Of the 62bn kg of e-waste generated globally in 2022, less than a quarter was formally collected and recycled in an environmentally sound way, according to a 2024 UN report.
Over 90% of PCBs are made in Asia, mostly China. The standard FR4 flame-retardant PCB can cost less than a pound but is not easily recyclable, says engineer Mahmoud Wagih at the University of Glasgow. ‘They can be shredded for recycling, which is a very energy-intensive process.’
A number of factors make recycling difficult and inefficient. Standard PCBs require fibreglass to be intimately woven into epoxy resin, a thermoset polymer that once cured cannot be softened by heat, only charred or decomposed.
They also contain brominated flame retardants, which generate toxic fumes when burnt.
Recyclers can recover metals such as gold and copper, but the non-metals often go to landfill.
Now, Jiva Materials in Hampshire, UK, has developed what it says is the world’s first fully recyclable PCB: Soluboard. The unique selling point is the carbon saving, validated at 68% when compared with the standard glass-fibre equivalent, FR4.
Jiva’s latest PCBs are made using Lyocell, a type of regenerated fibre made by dissolving plant cellulose – from bamboo or trees such as eucalyptus – and re-forming it into new fibres. The solvent, N-methylmorpholine N-oxide, can be recovered and reused.
‘The beauty of Lyocell is that it is an extruded product and we can make a nice weave,’ says Jiva CEO Stephen Driver. ‘It costs 15% to 20% more than jute, but eight times less than flax.’
The Jiva recipe is modified polyvinyl alcohol blended with natural fibres, along with a phosphorus-based flame retardant to replace the brominated flame retardant common in FR4. The polyvinyl polymer comprises about 70% of the material, with 25 to 30% fibre reinforcement.
‘Our reinforcement and our carrier is a natural fibre rather than an engineered glass fibre, which uses an awful lot of energy to produce,’ says Driver. The company claims that 590g of plastic is saved per square metre of Soluboard when compared with FR4.
Standard FR4 PCBs are a thermoset plastic, meaning two components become permanently combined after heating and curing. However, the Jiva board is a thermoplastic which means the polymers are blended together but can be separated later.
‘Ours gets broken down in water at 90°C,’ says Driver. That opens the door to recycling.
Wagih and his team have been collaborating with Jiva for about two years, jointly testing multiple versions of Soluboard. ‘What’s interesting is their surface finish avoids nickel, which makes copper and gold recovery simpler at end-of-life, creating a higher incentive for e-waste circularity,’ he says. While unlikely in the short term that these PCBs would be entirely recycled, it opens the possibility of recycling them with the right logistics in place.
Plant matter
Multiple EU projects are pursuing more sustainable PCBs. The Hyperlignum project taps wood by-products – containing cellulose fibres and lignin residues – as raw materials. Cellulose is a complex linear polysaccharide made from thousands of glucose units, which strengthens plant cell walls; it is the most abundant biodegradable and renewable polymer on Earth. Lignin is a crosslinked natural polymer of phenolic compounds, found especially in wood and bark.
Project scientists first break down the cellulose fibres in a disc mill, where they are disintegrated into fibrils as water is added. This paste-like mixture can then be dewatered under pressure in a press, to produce a rigid solid board that can be used as a PCB substrate. Austria-based industry partner Profactor prints conductor tracks on the substrates. Holes are drilled for electronic parts, which are assembled and soldered to the tracks.
Empa, a Swiss federal research institute, and Profactor researchers recently revealed a ‘green’ more sustainable circuit board made mostly from cellulose, with a small amount of lignin, integrated into a computer mouse also made from biodegradable material.
They reported on its mechanical properties, dimensional stability, electrical properties, surface uniformity and thermal conductivity (Scientific Reports; DOI: 10.1038/s41598-025-91653-1). Other project partners work on biodegradable nanoparticles conductive enough to potentially carry current on the PCB.
Another European project, CircEl·Paper, focuses on paper-based, multilayered PCBs. The project is demonstrating paper-based circuit boards for a glucose skin sensor, a time-temperature indicator for packaging, and a greeting card that plays music. ‘Paper has many advantages in terms of the circular economy, in particular high acceptance and widespread use for wastepaper recycling,’ explains Gerhard Domann at the Fraunhofer Institute for Silicate Research in Germany, which leads the project.
Indeed, the idea of wood-based electronics was a natural extension of the general EU-wide push for more wood in construction and infrastructure, says Valerio Beni, a printed electronics researcher at Research Institutes of Sweden (RISE) who heads up Hyperlignum and is also involved in the paper electronics project.
Nonetheless, researchers point out there are challenges in using biobased materials. Foremost of these is the fact that plant-based materials usually contain moisture and, if dried, retain an ability to absorb water. Cellulose contains abundant hydroxyl groups, which form hydrogen bonds with water molecules. This means that a cellulose-based PCB board can expand in moist or humid environments, disrupting electrical connections; if enough water is present, it could conduct current and short-circuit a device.
At Empa, the lignocellulose board developed by Geiger and his colleagues at 20°C and 85% relative humidity deformed by 0.81% to 0.95%, indicating instability in high humidity. However, while unsuitable for some humid environments, the board would still be useful for many indoor applications in a house or on an office desk, says Geiger.
Jiva’s Soluboard has not passed a standard industry test set at 85°C temperature, 85% humidity, but Driver is confident the technology will soon do so. The company believes there are many applications where their PCB will perform well enough with moisture. ‘Lots of regular PCB material shows a 1% uptake in moisture on spec datasheets, whereas typically ours might take up 3%,’ says Driver.
Heat can be another issue. Wood and paper cannot match the fire retardancy of fibreglass, so this needs to be factored into the design and deployment of wood-based PCBs. Jiva’s board, for example, uses a tin bismuth solder, which melts at just 138°C. The industry standard solder SAC305 is made mostly of tin and melts at 217°C. Switching to the lower-temperature solder, used at between 138°C and 170°C, reduces energy consumption by 40%, according to Jiva.
And while their lower fire retardancy may prohibit some applications of bio-based PCBs, plenty of consumer electronics will never encounter high temperatures.
Glassy polymers
Natural polymers are not the only route to greener PCBs. At the University of Washington, US, researchers have investigated transesterification vitrimers to make PCBs easier-to-recycle. Vitrimers are a newer type of crosslinked polymer that behave like a rigid thermoset, including at room temperature, but above certain temperatures their covalent crosslinks can unclick and re-click, behaving more like thermoplastics.
This allows for greater repairability and recyclability. ‘Once you heat above a certain temperature, these polymers undergo exchange reactions that allows the polymer to rearrange and retain its original properties once it cools down to room temperature,’ explains mechanical engineer Aniruddh Vashisth.
The Washington group formulated a new type of PCB by combining transesterification vitrimers with glass fibres to construct a composite.
Using their new PCBs, the team created a number of devices such as a prototype IoT wireless temperature sensor. A recycling process removed the copper and then added a solvent to swell the vitrimer matrix and separate it from the glass fibres without chemical breakdown (Nature Sustainability; DOI: 10.1038/s41893-024-01333-7).
‘Within hours at room temperature, it swells and we recover most materials, opening up the potential for circular manufacturing,’ says engineer Vikram Iyer; the recycling process recovered 91% polymer, 100% fibre and 91% solvent. ‘We tested our PCB mostly against FR4 and most of our specs were on par.’
The standard FR4 dominates the market in terms of volume but it is not the only game in town.
A composite made of paper impregnated with phenolic resin, FR2, is a cheaper PCB often used in toys or household appliances, while FR3 is paper, phenolic resin and epoxy resin that has a slightly better performance than FR2 but not to the level of FR4. There are also ceramic PCBs with higher performance in heat dissipation, high dielectric constants and reliability, used in medical and radiofrequency devices and in radar systems.
‘Critical satellite applications, like antennae, need a single material that is homogeneous and isotropic – same properties in every direction – and so use ceramic PCBs,’ explains Wagih.
This is partly due to surface topography, something that natural fibres struggle with. A signal that needs to travel from A to B can do so easily across a shiny flat surface, but the signal can be attenuated or reflected if it must traverse a more bumpy and non-uniform natural surface.
Meanwhile, there are also aluminium-based PCBs – popular for LED lighting and power conversion, as well as aerospace applications. While there is already a range of PCB options on the market, incentives for more sustainable PCBs are expected to increase, especially in Europe.
The EU has set goals of e-waste reduction and ‘right to repair’ regulations set to impact PCB design choices. There are no specific regulations targeting PCBs, but a sustainable products regulation is being discussed, as well as a digital product passport, which would require material composition information and encourage standardised material. Meanwhile, companies themselves have set carbon reduction and recycling targets.
Jiva has designed its new ‘greener’ boards to be a drop-in replacement so that it can go into a standard PCB factory. Initially the boards will be made in Hampshire, UK. ‘We’re making PCB material every day. Our revenue [in 2025] will be less than half a million, but we have got customers and we are making stuff,’ says Driver.
Market opportunity
Recently, the University of Glasgow has demonstrated that Jiva’s PCBs can transmit signals at frequencies above 4GHz, which covers common wireless applications such as WiFi, Bluetooth and RFID.
The group will continue to work with the company on new designs to improve efficiency. ‘We are supporting Jiva with building application demonstrators with reliable RF [radiofrequency] performance, from low-cost environmental sensors to more specialised RF and microwave circuits working up to 20GHz,’ notes Wagih.
Jiva Materials is a front-runner, but the company does not expect to be alone in the sustainable PCB space. ‘This is a $95bn market so there is plenty of room for startups,’ says Driver, of the current PCB market.
‘We want to remain the leader, but the more the market gets validated the better for us. If the OEMs [original equipment manufacturers] start designing their product around an environmentally friendly material, they will want back up suppliers. We want the competition.’
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