Terasel is an EU-backed research consortium studying flexible electronics.
According to their site:
The TERASEL project envisions a world where non-intrusive electronics are integrated everywhere. To achieve this twenty-first century dream using reliable and economical techniques, the TERASEL consortium targets to exploit today’s technology in new and exciting ways. Free-form 2.5D and full 3D electronics are highly desirable for various reasons.
They offer various advantages like better aesthetics, higher user comfort, increased safety, reduced complexity, ecological products due to lower material usage, design freedom, and many others.
The aim of the TERASEL project is to establish and demonstrate a complete industrial production chain for the fabrication of randomly shaped electronics and sensor circuits. In this project the EU research institutes and companies leading the worldwide technology developments and industrialization efforts on large area elastic circuits will take full advantage of their position to tackle the challenge of developing, applying and industrializing the technology for thermoplastic one-time deformable circuits.
To achieve this daunting task in three short years the TERASEL project revisits the stretchable electronics technology developed in previous European projects like STELLA (Stretchable Electronics for Large Area Applications) and Place-It (Platform for Large Area Conformable Electronics by inTegration). TERASEL offers three technologies to achieve this goal, each coming with its own advantages. Compared to the competing technologies some of the key advantages are the capability to integrate a wide variety of electronic components, support for power applications with high currents and voltages, and usage of standard equipment from the circuit board industry. All of this is made possible by starting from a conventional flat substrate with a stretchable circuit which is deformed to the desired 2.5D or 3D later on using conventional thermoforming.
I’m going to repost their technology and links pages for posterity:
|To make it possible to deform a flat assembly to the desired 2.5D shape the embedded electronics have to be able to deform as well. This is achieved by introducing the concept of stretchable circuits by which flexible or rigid component islands are interconnected using stretchable electrical interconnects. This way a flat circuit can be deformed to any desired shape and still remain functional.
For embedding and forming these structures in combination with a wide variety of materials the consortium relies on the expertise of several industrial partners, together with the expertise of a world renowned institute on injection molding (PEP), to offer a wide variety of possibilities. By doing so, we hope to meet the requirements for the most challenging applications.
Niebling Formtechnologie, the inventors of isostatic high pressure forming, brings their expertise in the forming of polymers and conductive features to the project. High pressure forming offers, among many other benefits, very high positioning tolerances and compatibility with a wide variety of materials. For industrial scale vacuum forming and injection molding SINTEX NP is the partner of choice, having a long track record of high volume production for various industries like automotive, aeronautics and medical. They are able to bring even the largest scale applications to life.
|Stretchable Mould Interconnect
Imec’s SMI technology was previously used to encapsulate fully stretchable circuits in both silicone (PDMS) and thermoplastic polyurethane (TPU). It is based on copper meanders supported by polyimide. By introducing a high temperature carrier with a reusable adhesive, to which the polyimide substrate is attached during production, it is within TERASEL the only technology which allows high temperature lead-free soldering. In fact the carrier allows the use of standard printed circuit board processing without any further modifications to the process. After the definition of the meanders the circuit is transferred to a polyurethane film and embedded in a thermoplastic material using lamination or injection moulding.
|Stretchable Circuit Board
Fraunhofer IZM’s Stretchable Circuit Board (SCB) technology directly integrates a copper layer on a polyurethane film which is mounted on a temporary carrier. The copper meanders are patterned using conventional photolithography and etching steps. Subsequently, the patterned copper is covered with polyurethane. The components are assembled using low temperature solder and capped off by polyurethane. The end result is embedded in a thermoplastic sheet, which can be deformed later on, using lamination or injection moulding.
|Stretchable Plastic Film
TNO Holst’s Stretchable Plastic Film technology takes a different approach by introducing the concept of additive manufacturing to the printed circuit board world. The process starts by screen printing a layer of conductive paste on a thin plastic film. The electronic components are assembled using conductive adhesive. To protect the components, and to embed the film in a thermoplastic material, the whole system is first embedded in a layer of thermoplastic polyurethane which is then laminated to a thermoplastic material.
|High Pressure Forming
High Pressure Forming is one of several methods to deform sheets to a desired free-form shape. It works by heating the sheet to its glass transition temperature using contactless infrared heaters. Next, the sheet is formed against a metal tool using compressed air. Its main characteristics are support for a wide variety of materials, lower temperatures, and high positioning tolerances.
Injection molding is one of the most common techniques to make plastic parts. It offers high precision, the ability to make complex parts, and above all flexibility in choice of materials. The process starts by melting plastic pellets; these are then injected under high pressure in a mold. After a short cooling time the mold opens and the part is ejected.
Vacuum forming is one of the workhorses of the plastics industry. It is a cheap and reliable way to make plastic parts with low setup costs. This makes it an economic approach for both low and high volume applications. First the sheet is heated to the point where the plastic becomes formable using a variety of methods (e.g. infrared heaters). It is then drawn into a forming tool using a strong vacuum. This forces the plastic to take the shape of the forming tool.
A short overview of links relating to deformable electronics and the Terasel project in general.
|7th Framework Programme
The Seventh Framework Programme (FP7) bundles all research-related EU initiatives together under a common roof playing a crucial role in reaching the goals of growth, competitiveness and employment; along with a new Competitiveness and Innovation Framework Programme (CIP), Education and Training programmes, and Structural and Cohesion Funds for regional convergence and competitiveness. It is also a key pillar for the European Research Area (ERA).
Platform for Advanced Smart Textile Applications
Platform for Large Area Conformable Electronics by InTegration
Stretchable Electronics for Large Area Applications