Stretchable electronics manufacturing and application

Abstract

In the recent years the fabrication of electronic systems that can to a certain extent be stretched has attracted increasing attention. As general motivation such electronics will in contrast to conventional electronics be compliant with free form shapes, as for example the human body surface. A number of different successful approaches to realize such systems have been demonstrated. Thus far various aspects of stretchable electronics have been addressed ranging from stretchable Si detector arrays to large scale, low cost stretchable systems with integrated commercial components. Within the EU project STELLA the latter types of fabrication technologies have been developed. These technologies are presently further developed with focus on optical applications in the project PLACE-it. The rationale of both projects is the use of conventional printed circuit board technologies for the fabrication of stretchable wiring substrates onto which components are assembled and embedded. Stretchability is accounted for by a meandering layout of the Cu-interconnects between components and the rubber like polymeric substrate polyurethane, instead of polyimide which is used in conventional flex-prints. In the present paper basic features of the fabrication process for stretchable substrates will be discussed. Selected materials, process parameters and design aspects will be addressed with respect to selected target applications. Reliability requirements of stretchable systems are very much dependent on the application scenario. Besides obvious stretch-to-failure, cyclic stretching and bending tests, also robustness with respect to cleaning and washing is required. Comprehensive reliability standards are yet to be defined. In the present paper a brief overview of reliability assessment will be given. A few of the realized applications using stretchable electronics will be presented and discussed. The versatility of the fabrication technology and its products will be emphasized. The potential impact on different application fields will be highlighted, as for example electronic integration into textiles and in automotive applications.