The new material has nearly the same performance as traditional PCB material but can be completely recycled.
Researchers from the University of Washington have developed a new formulation for circuit boards that offers performance on par with traditional PCB laminates but can be recycled repeatedly without degradation. The breakthrough could help prevent tons of e-waste from being tossed into landfills as PCBs become broken or obsolete.
Traditional PCBs are manufactured using sheets of glass fibers laminated in an epoxy resin, such as those found at hardware stores, which is then subjected to pressure and heat to form an integral final piece of uniform thickness. The composite material is what gives the board its strength, heat resistance and dielectric properties. It's also why it's difficult to recycle the PCBs, as the materials are difficult to separate, which is why some are typically burned to recover valuable metals like gold and copper used in electronics. That burning process also creates waste that contaminates the environment.
“PCBs make up a pretty large fraction of the mass and volume of electronic waste,” states Vikram Iyer, a UW assistant professor in the Paul G. Allen School of Computer Science & Engineering. “They're constructed to be fireproof and chemical-proof, which is great in terms of making them very robust. But that also makes it basically impossible for them to recycle. Here, we created a new material formulation that has the electrical properties comparable to conventional PCBs as well as a process to recycle them repeatedly."
Iyer and his team of researchers replaced the epoxy with vitrimer, a type of plastic derived from thermosetting polymers. Vitrimers form new, strong chemical bonds when heated past a certain temperature, allowing them to be recycled repeatedly, unlike the plastic used for water bottles, which degrades during each recycling cycle.
To recycle the vitrimer material, it's first stripped from the glass fibers that form the substrate of the PCB, which is done by dipping the board into a solvent, then heating it to a mild temperature. The process softens and swells the material, allowing the researchers to separate the raw materials and use them to create a new PCB. During experiments, the researchers managed to reuse 98% of the vitrimer and 91% of the solvent while recycling the material multiple times without losing its properties. The performance difference between vitrimer and traditional PCB composites is negligible, meaning future PCBs could be manufactured using the new material with little cost increases, as the process of manufacturing the boards is nearly identical to producing traditional boards.
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