Unique Roll-to-Roll Laminator Enables Unrivaled Alignment

Researchers at Holst Centre have used a unique laminator and a novel control strategy to achieve alignment of 70 microns between two foils in a roll-to-roll process. Through “sheet-by-sheet” adjustments, Holst Centre’s approach delivers faster, more accurate alignment, cutting waste and costs. The strategy promises further improvements, enabling roll-to-roll manufacturing of more advanced flexible electronics circuits.

Flexible electronics devices are built up from multiple layers of design features. Layers may be produced on separate foils, which must then be laminated together to create the final device. During the lamination process, the foils must be accurately aligned to ensure a good connection between layers so that the end device works properly. As devices become more advanced and features get smaller, more accurate alignment is required.

The Holst Centre team has achieved alignment accuracy better than 100 µm in two dimensions simultaneously. This new benchmark was set using a unique roll-to-roll laminator. This custom-made machine was designed by Holst Centre and manufactured by coating and laminating equipment specialists Coatema. Holst Centre has also developed a brand new control system to maximize alignment accuracy.

In this new strategy, the foil on one of the rolls is divided into sheets by carefully designed “weak zones.” Each sheet is measured separately, and the weak zones allow the position of each sheet to be adjusted individually without tearing the foil. This means accurate alignment can be achieved much more quickly, avoiding the meters of wasted material typical of today’s roll-to-roll lamination systems.

Sheet-by-sheet alignment also ensures better response to the inherent variability of flexible electronics production, improving yields. In addition, the system works at low tension, reducing the risk of breaking the foil’s barrier layer.

“We believe our system is the only roll-to-roll laminator capable of aligning separate sheets on a roll individually. This approach will help manufacturers greatly improve the economics of flexible electronics by reducing the waste of expensive raw materials,” said Irene Kaashoek, control engineer in Holst Centre’s Integration technologies for flexible systems program.

“We are very pleased that Holst Centre has added this unique tool to its equipment portfolio,” said Philipp Weissel, CEO plastic electronic, an Austrian SME and research partner at Holst Centre. “It adds value to our partnership and will be of benefit for the manufacturing of our flexible electronic products, such as the StoreSkin, a pressure-detection foil for smart shop-shelve applications.”

Looking to the future, Holst Centre’s new control strategy offers scope for further alignment improvements. Combining it with more sophisticated mechanical system should allow alignment to be pushed well beyond today’s 70 µm benchmark, enabling flexible electronics to evolve to smaller feature sizes and more advanced devices.