Printed circuit boards (PCBs) are a major component of e-waste, the fastest growing type of waste globally. This item is currently made from non-biodegradable and hard-to-recycle substances but researchers think that making them from biobased ingredients is a firm possibility.
What are circuit boards made of?
Most PCBs in use today are designed with function and cost in mind rather than considerations about what happens once the product is no longer in use.
The environmental risks become apparent when looking at the ingredients list for the most commonly used material for PCBs. Known as ‘FR-4’, it is a mixture of woven glass fibre, epoxy resin and copper foil.
FR-4 starts with a composite of paper and glass fibre – known as composite epoxy material – woven together to form fabric-like sheets which are dipped in epoxy resin. Epoxy resin is a thermosetting plastic which provides a protective, electrically insulating layer that prevents short-circuits.
The entire surface of the FR-4 base layer is coated with a sheet of copper. A chemical is used to ink out the final circuit design invisibly on the copper. When the entire thing is dipped into a corrosive chemical bath, the excess areas of copper dissolve away, leaving just lines of the metal marking out the chemically traced circuit design. Silver ink can also be used to trace out the circuit board though copper is more common.
What’s wrong with PCBs?
FR-4 is so popular for PCBs because the materials used in it can resist moisture, chemicals, and heat. However, FR-4 is able to perform so well precisely because of the toxic chemicals inside them.
Apart from epoxy, other resins might be used to stiffen the fibreglass sheet. These might be cyanate ester, polyimide, polyester. Yet regardless of what exactly they’re made from, most PCB materials are not environmentally safe for human or environmental health. One of the most ex-toxic of the PCB’s ingredients is halogenated flame retardant, which causes cancer and disrupt neurological function in humans and animals.
This is concerning because less than 20% of used PCBs are collected for recycling. The economic incentives are simply not there, with processing used boards being costly, inefficient, and lacking well designed-collection systems.
This lack of policy around e-waste management means most circuit boards end up dumped in landfills where their synthetic polymers release a cocktail of toxic chemical compounds.
How can biobased boards help?
Biodegradable circuit boards would go a long way towards making electronic waste less environmentally hazardous.
Biobased materials for PCBs address the environmental problems with existing circuit boards in two ways: they cut PCB eco-toxicity at the end of their working lives and also cut the emissions that come with manufacturing them in the first place.
Researchers say paper-based circuit boards contribute far fewer global warming emissions than FR-4 and are measured far better on every environmental impact indicator for its full life cycle, except for land use (paper needs forests, after all).
What kind of biomaterials can go into a circuitboard?
What materials could be used to achieve a biobased and circular circuit board?
We should remember that a printed circuit board is a relatively simple concept: the board is just an instruction booklet or a sort of electronic map. This is why for basic prototyping purposes, engineers can even work with simple paper or cardboard, drawing circuits manually with metal inks.
This is why in demo projects at least, materials such as paper, flax and biobased resin matrices in prototype PCBs were seen to be effective substitutes for FR-4.
They were also shown to reduce the environmental impacts of PCB materials and improve recovery and reuse of metals and electronic components, minimise the use of toxic flame retardants, and provide pathways for safer end of life management.
Theoretical possibilities for PCB materials include even banana and cellulose fibres although these have not been made into functional prototypes.
However, the challenge is getting such low resource-intensity materials to work practically on a commercial scale. For example, paper is fine for prototyping but not rigid enough to serve as a durable PC component. It is also not flame retardant which is a problem when hand-inked metal circuits are replaced by heat-intensive assembly processes like soldering.
Hampshire company leads in biobased PCBs
One company that has worked out a way to commercialise biobased circuit boards is Jiva Materials, a company based in Hampshire in the UK. The company claims to have created the world’s first fully recyclable rigid printed circuit board, branded as the name Soluboard.
The recyclability of its PCB comes from its natural fibre content, which replaces the glass-fibre and epoxy resin of conventional board manufacturing.
In Jiva Material’s circuit board making process, woven fibres are not made from plastic or glass but rather from natural unprocessed materials. The woven fibre fabric is then dipped into a water soluble polymer and halogen free flame retardant. The natural materials are meant to reduce the overall carbon footprint of the product compared to the conventional manufacturing route. The halogen-free retardant makes for a slightly less harmful product.
Cutting down on eco-toxic materials doesn’t just reduce the amount of carbon the PCB releases. It also makes the circuit board and everything that’s printed on it more easily recyclable. Once the circuit board has come to the end of its life, The organic board can be dissolved in hot water in a controlled environment, leaving behind just the copper, any other valuable metal components, and the natural fibres – all ready to be re-used. The water-soluble circuit board could reduce the high cost problem impeding circuitboard recycling today.
Jiva’s research into biobased PCBs are ongoing. The company is testing the properties of other natural fibres like jute, flax, and hemp as potential laminate materials in collaboration with the University of Southampton.
According to the project advisor Stephen Woodhouse, it is supposed to scale Jiva Materials’ product while allowing the company to pursue more technical innovations through exposure to university researchers in the materials space.
Chip maker pilots biobased boards
Jiva Material customer Infineon Technologies set out to pilot the biodegradable Soluboard in consumer applications. Last year, Infineon manufactured 500 units of three different kinds of PCBs using the Soluboard material to reveal how the semiconductors on the biobased boards can be re-used and recycled.
Infineon is a semiconductor specialist based in Germany, a Siemens spin-off founded in 2009. Trailing the Soluboard is part of the company’s strategy to reduce the carbon footprint of demo and evaluation boards, which are used to test the functionality of PCB desgins.
The company says that the drive to reduce the carbon emissions of its electronic products flow from the EU Commission’s Green Deal climate neutrality goal, suggesting that there might be a wave of new demand from EU electronics manufacturers for bio-based PCB innovation in the near future.
Microsoft invests in sustainable PCB research
Microsoft is also looking at more sustainable PCB substrate materials built using renewable materials.
It is doing this in collaboration with the University of California Irvine WISDOM research group, where a team is looking at biodegradable and non-toxic PWB materials and working out a best practice framework for manufacturing sustainable circuit boards.
In 2022 a Microsoft team published a Nature article on the possibility of replacing polymers, resins, and other synthetics with biobased alternatives, indicating both more research into new materials is needed and regulatory policies for electronic waste management.
Electronics that disappear
Some researchers dream of an entirely different paradigm of resource use in electronics where fully biodegradable products are the norm.
In this technological vision, all materials used to make hardware can be collected and re-used in some sector or another at the end of its life: a paper circuit board that degrades into nutrient-rich mulch for agriculture can also release any critical minerals from the circuitboard in the process, ready for re-use in electronics and industry.
We may be far from achieving ephemeral plant-based electronics but there is already optimism that using some biobased materials in common components can help reduce the environmental hazards posed by e-waste.
