SMTA International Conference Proceedings


Authors: Thomas Löher, Ph.D., Manuel Seckel, Rene Vieroth, Andreas Ostmann and Herbert Reichl, Ph.D.
Company: Technische Universität Berlin and Fraunhofer IZM
Date Published: 10/4/2009   Conference: SMTA International

Abstract: In an increasing number of novel electronic applications the ability of an electronic system to comply with a certain degree of elongation is requested. Such elongations may either be a single stretching during the fabrication process, or the system may be subjected to repeated stretch and release cycles. Different technical approaches to add elasticity to electronic circuitries have been developed and investigated during recent years. In the present paper a short overview of these technologies will be given. One particular technology will be treated in more detail, which makes use of conventional fabrication technologies for printed circuit boards. The non-conventional building blocks of the realized stretchable circuit boards are (i) the stretchable matrix material, thermoplastic polyurethane, and (ii) meandering copper conductors between electronic components. With minor support measures such boards can be handled and treated like rigid printed circuit boards throughout the fabrication process. For component assembly onto the stretchable circuits again conventional process technology applies: solder printing, pick and place, reflow. The only constraint -due to the physical properties of the stretchable matrix- is the use of a low temperature solder alloy like SnBi and the respectively low reflow temperature. After assembly the components are usually encapsulated with polyurethane. So far a number of stretchable electronic applications have been realized. The examples which will be presented in the present paper are a band aid with embedded sensors and a control unit and the integration of stretchable systems into textiles

Key words: stretchable electronics, embedding, textile, polyurethane.

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