Flexible substrate dissolves to combat e-waste
Researchers in the US have developed a degradeable flexible substrate that could help to tackle increasing amounts of electronic waste.
The flexible substrate material was developed at MIT, the University of Utah, and Meta also enables manufacture of more complex multilayered circuits.
“We recognize that electronic waste is an ongoing global crisis that’s only going to get worse as we continue to build more devices for the internet of things, and as the rest of the world develops,” says Wallin, an assistant professor in MIT’s Department of Materials Science and Engineering.
Most research has focused on different polymer materials to polyimide, but “that really ignores the commercial side of it, as to why people chose the materials they did to begin with,” says Wallin. The polyimide business is projected to be a $4 billion global market by 2030. “It’s everywhere, in every electronic device basically,” including parts such as the flexible cables that interconnect different components inside your cellphone or laptop says Prof Chen Wang at Utah.
Soluboard from Jiva materials in the UK is a similar rigid PCB technology that can be dissolved and has been used by Infineon for a demonstrator with power devices.
However, it’s also virtually impossible to melt or dissolve, so it can’t be reprocessed. The same properties also make it harder to manufacture the circuits into advanced architectures, such as multilayered electronics.
The alternative material that the team developed, which is itself a form of polyimide and therefore should be easily compatible with existing manufacturing infrastructure, is a light-cured polymer similar to those now used by dentists to create tough, durable fillings that cure in a few seconds with ultraviolet light. Not only is this method of hardening the material comparatively fast, it can operate at room temperature.
The new material could serve as the substrate for multilayered circuits, which provides a way of greatly increasing the number of components that can be packed into a small form factor. The fact that the new material can be processed at low-temperature while also hardening very quickly on demand could open up possibilities for new multilayer devices, says Wang.
The team introduced subunits into the polymer backbone that can be rapidly dissolved away by an alcohol and catalyst solution. Then, precious metals used in the circuits, as well as entire microchips, can be recovered from the solution and reused for new devices.
“We designed the polymer with ester groups in the backbone,” said Wang. These ester groups can be easily broken apart by a fairly mild solution that removes the substrate while leaving the rest of the device unharmed. The University of Utah team has co-founded a company to commercialize the technology.
“We break the polymer back into its original small molecules. Then we can collect the expensive electronic components and reuse them,” Wallin adds. “We all know about the supply chain shortage with chips and some materials. The rare earth minerals that are in those components are highly valuable. And so we think that there’s a huge economic incentive now, as well as an environmental one, to make these processes for the recapture of these components.”
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