Taming E-Waste with Dissolvable Circuit Boards

Between ubiquitous computing, new sensing technologies, and other recent advances, electronics are showing up in almost everything. While this is a positive change that offers us many previously unheard of conveniences, the low cost and pervasiveness of these devices is also leading to them winding up in the trash at a rapidly accelerating rate. The fact of the matter is that the components are so inexpensive that going through the complex procedures necessary to recover them simply does not make good economic sense.

It is becoming increasingly clear that we need to rethink the idea of disposable electronics. According to the United Nations, electronic waste generation is rising by 2.6 million tons per year, and is on track to reach 82 million tons by 2030. The components in this waste contain toxic materials that leach into the environment and harm both wildlife and humans. We do not want to just give up our technological advances that make our lives better, however, so we urgently need better methods to control electronic waste generation.

Help may be on the way, thanks to a joint effort by researchers at MIT, the University of Utah, and Meta. They have developed a new type of flexible substrate material that can be used in place of traditional circuit boards. This novel material can be dissolved away with a mild solution to easily and safely release the components for reuse or recycling.

A number of similar efforts have been undertaken in the past, but they tend to rely on the use of unusual materials that are nothing like those presently used in circuit board fabrication. The problem with this approach is that present materials were chosen for good reasons — like high levels of heat tolerance and economic considerations — so it may be completely impractical to swap in a new material that does not check all of these boxes.

In this case, the team went with the tried and true material called polyimide. Traditionally, it is impractical to recycle boards made with it because it first needs to be heated to up to 300 degrees Celsius to reach its melting point. But by adding ester groups to the polyimide’s backbone, the team found that it could then be completely dissolved, at room temperature, by adding a mild alcohol and catalyst solution. That makes it possible to scavenge the embedded electronic components without any complex or expensive procedures.

This new material also benefits the design of multilayer circuits, which is especially useful when trying to pack a device into a tiny form factor. Whereas polyimide boards normally need to be glued together to create a stack of layers, since the melting point is so high, the new material is cured by light, which makes it much easier to join them. This makes the production of compact devices much more cost-effective.

It was noted that the new material does change some properties of the polyimide, which could render it unsuitable for some applications. Moving forward, they plan to investigate how certain particulate fillers could, for example, enhance the material’s thermal conductivity.