New tracks: copper-based inks for printed electronics

Richard Dixon - 18 Jun 2010

Copper-based ink would be a major step forward for printed electronics, says Richard Dixon, COO of nanotechnology firm Intrinsiq Materials.

The printed circuit board (PCB), the backbone of electronic circuits, is found in virtually all modern appliances and therefore represents a huge opportunity for new cost-reducing innovation and process development.

Traditionally copper has been used for electrical circuits, due to its relatively low cost, abundance, conductivity, long-term stability and ease of deposition by electroplating.

Process

Conductive tracks are produced by a complex and expensive multi-stage chemical process, typically using photomask imaging: copper laminate materials are coated with a photoresist material, which selectively patterns using ultraviolet light. The remaining image is copper electroplated to obtain the final desired conductor thickness, with a protective layer, such as tin, then plated on top. Over the last 50 years, chemicals and the etch and plating processes have been honed, resulting in mass-produced PCBs that meet ever-increasing electronic requirements.

Though this wet system of production is successful, it does have its limitations. There are environmental problems in disposing of spent chemicals; the process is best suited to flat substrates; it can only be used with limited substrate materials; and it requires extensive capital plant.

The process is complex, expensive and requires close control. Due to initial circuit setup costs it is best suited to long production runs.

The advent of an additive process like printed electronics, where only materials that contribute to the final circuit are deposited, could replace standard PCB technology in the long-term. Printing three-dimensional structures and on low-temperature substrates, such as plastics and paper, could also open up new product areas.

Inks

Technology developed by Intrinsiq Materials, which uses the inkjet printing of copper nanomaterial-based inks followed by a room temperature photonic curing process, means printing metallisation layers for thin-film transistors, displays and solar cells is now possible, as are new applications like printing RFID tags or other sensor technology, such as temperature monitoring, directly onto packaging.

Cost reductions compared to traditional manufacturing technologies are achieved not only in providing a simpler manufacturing process, but also faster product development times as prototyping is more easily undertaken.

Want to read more?
This article appears in full in Volume 3, issue 1 of +Plastic Electronics magazine, explaining the work being done to make copper inks suitable for printed electronics, describing how Intrinsiq's technology works and discussing the company's plans for commercial scale-up.
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