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Realization of large area stretchable electronic systems using lamination processes

: Loeher, T.; Manessis, D.; Ostmann, A.; Reichl, H.

International Microelectronics and Packaging Society -IMAPS-:
EMPC 2007, the 16th European Microelectronics and Packaging Conference & Exhibition. Proceedings. Pt. 2 : June 17 - 20, 2007, Oulu, Finland
Oulu, 2007
ISBN: 978-952-997511-2
European Microelectronics and Packaging Conference and Exhibition (EMPC) <16, 2007, Oulu>
Fraunhofer IZM ()

Electronic systems that can be stretched to a certain extend have attracted much attention in recent years. A multitude of potential applications ranging form medical implants and health monitoring to skin like electronic surfaces for robots and application of electronics systems to complex three dimensional surfaces are conceivable. Stretchability is in short an additional feature to an electronic system that increases the freedom in design of potential products. Besides more freedom in design such systems will offer a higher degree of reliability if properly designed and fabricated. A variety of approaches to fabricate stretchable electronic systems are pursued at present. At TU Berlin a process that makes as much as possible use of conventional printed wiring board technologies was developed that offers the capability produce stretchable systems with large areas at relatively low cost. Core process is the attachment of stretchable material to full area copper sheets, the subsequent structuring of the copper layer into separated conductor lines and bond pads for component assembly. After assembly of the components a covering layer of the stretchable material is applied to fully embed and protect the components in the stretchable matrix. The attachment of a stretchable material to a copper foil in the first step yields best results in a conventional lamination process. Structuring of the copper layer is achieved by photolithography or comparable processes combined with etching. In order to impart stretchability to the copper, conductors will be meandering. The transition between more (areas free of components) and less stretchable portions (surrounding of embedded compact electronic components) deserves special attention in the design of the stretchable system. Therefore mechanical reinforcements structured out of the copper layer have been used, different kinds of stiffeners and encapsulations are conceivable. The final embedding of the electronics by a capping l