Landfills around the world are increasingly being inundated with electronic waste (e-waste). Worldwide, approximately 62 million metric tons of e-waste were generated in 2022, according to the Global E-waste Monitor report. This figure is expected to grow to 82 million metric tons by 2030. Despite its growth, only around 22 percent of e-waste was officially documented as being collected and properly recycled, leaving a large portion unaccounted for and likely ending up in landfills. This massive accumulation of e-waste presents significant challenges for the environment and public health.
Many electronic devices contain hazardous materials such as lead, mercury, cadmium, and brominated flame retardants. When improperly discarded in landfills, these toxins can leach into the soil and groundwater, posing a serious threat to the environment and human health. Additionally, when e-waste is incinerated, it releases toxic fumes into the air, contributing to air pollution and respiratory problems for nearby populations.
Vitrimer dissolving in a solvent (📷: Mark Stone / University of Washington)
A major factor contributing to low recycling rates is the fact that the make-up of present PCBs render them difficult to recycle. They are composed of layers of glass fiber, hard plastics, and copper that have been laminated together, along with the electronic components that are soldered to the board. The layers are very hard to separate, so the effort required to recycle PCBs is often seen as outweighing the benefits.
A completely new type of PCB developed by a group led by researchers at the University of Washington may change all of that in the near future. Using a novel material, the team managed to produce a PCB that can be dissolved when it is no longer needed, allowing the electronic components to easily be scavenged for reuse. And the dissolved material itself can be reused to make another PCB.
The PCBs are composed of a sustainable polymer called vitrimer. Through a simple process, it can be made into high-quality PCB layers by fusing with glass fiber sheets. But when exposed to a solvent, the vitrimer turns into a jelly-like substance and dissolves away. The researchers found that by using this technique, they could recover 100 percent of the glass fiber, 98 percent of the vitrimer, and 91 percent of the solvent for reuse. Unlike traditional plastics, vitrimer is not degraded by recycling, so it can be reused indefinitely.
Manufacturing a PCB in the lab (📷: Mark Stone / University of Washington)
The manufacturing process for these new PCBs is very similar to the process used to make traditional boards, so the switch should not be too challenging for existing manufacturers. Furthermore, experiments showed that the electrical properties of the PCBs were quite good and comparable to PCBs made of FR-4, the most commonly used material today. Given these factors, this type of recyclable PCB could potentially start appearing in our electronic devices in the future.
When it is time for a board to be recycled, it is a relatively clean and environmentally-friendly process. The researchers calculated that recycling the new boards would result in an 81 percent reduction in carcinogenic emissions, as compared with FR-4 PCBs. But only time will tell if these eco-friendly PCBs can stand up to the often difficult conditions faced by real-world applications.