Most PCB recycling processes are hazardous and have serious health risks. To solve this problem, researchers are already studying the materials, and fortunately biodegradable PCBs are not a far-fetched solution now.
You may have thought it is impossible to make dissolving PCBs, but they’re already here. Some researchers have made a water soluble PCB that measures temperature data and transmits that data wirelessly. The conductors in a dissolvable circuit are made from transient metals, such as tungsten or zinc. While these metals are not currently as conductive as copper, silver, or gold, researchers are working on increasing their conductivities. Replacing current metals, which can be toxic, with transient metals would be a big step forward.
The other side of the environmental equation is the PCB substrate. There is a wider variety of materials being studied for use in substrates. Everything from chicken feathers to soybean oil, to sodium carboxymethyl cellulose (Na-CMC). With multiple candidates, there are more opportunities for different substrate specifications as well.