Researchers pursue biodegradable pc boards

Researchers pursue biodegradable pc boards
CAMBRIDGE, England — A project to investigate reducing the cost of recycling has produced some promising results — and a patent application — in the area of biodegradable printed-circuit boards.

The Welding Institute (TWI), based here, and the British Textile Technology Group (BTTG; Manchester, England) have been working together for about one year and are now looking for additional partners to help produce an industrial-scale demonstration of the technology.

TWI has been investigating biodegradable pc boards as a means of satisfying forthcoming European Union (EU) recycling legislation. Candidate materials for biodegradable pc boards include proteins such as casein and plant extensions and carbohydrate-based materials such as cellulose and chitin, said Dosten Baluch, business development manager at TWI.

"The EU is considering a new directive, the Waste Electronic and Electrical Equipment directive, which has to be fully implemented within five years. Manufacturers will be required by law to take back their products after their useful life and will be responsible for recycling 90 per cent of the material. It won't be allowed to go to landfill or be incinerated," Baluch said. "At the moment PCBs are sent to incineration, which is becoming unacceptable."

A a result of those moves, disassembly is becoming a necessary part of system design. However, designing for that eventuality with current materials has serious limitations, Baluch said. With biodegradable materials "it would be possible to drop PCBs into a reactor and separate materials by flotation."

Baluch said the project would characterize a number of materials and structures in terms of mechanical strength, stiffness and stability, as well as dielectric properties and thermal behavior. "For the printed wiring board application we are looking at, the best way of making the materials would be in thin layers bound together with plastic to achieve the right performance characteristics. We envisage a similar type of construction to fiber-glass epoxy laminates, except that it would use a biodegradable plastic. In a suitable solution the plastic would fall apart, allowing components and metals to be recovered. The remaining organic material might then be suitable for fertilizer or animal feed," he said. The project would also examine the in-service stability of biodegradable boards to make sure degradation can only take place at the end of life.

Making sure materials can withstand processing temperatures will be one of the major challenges, Baluch said. "The temperatures of solder baths are 140 to 230 degrees Centigrade. Cellulose-based materials can certainly tolerate temperatures like that but we need to investigate further as the banning of lead-based solder, also contemplated by the European Union, could require the use of solder at higher temperatures.

"Housings are usually made from thermoplastics, which are not very good for recycling," he said. "We have a ceramic coating on biodegradable plastic that is a good candidate for an alternative. While the coating is complete it maintains the structural integrity. To dispose of the material you cut it up to expose plastic that can be broken down."

There are three routes by which the research may be taken forward, Baluch said. "We already have a consortium of interested companies and are in a position to submit a proposal for support under the European Union's Fifth Framework collaborative research program.

"It could be funded by venture capital. We have interest from a couple organizations. Or thirdly, we could seek commercial sponsorship from the Far East. The Japanese are much more active in green electronics than Western Europe or the U.S.," Baluch said. TWI and BTTG will decide how to take the research forward by November of this year, he said.