Conformal Electronics on Elastomers Packaging Methods and Design Rules

Abstract

Flexible Electronics is a multi-disciplinary domain that creates intersections among elec- tronics, materials-science, mechanics, packaging, sensor-design, etc., to build exible / stretchable / conformal electronic circuits and systems. The spectrum of this field is very broad, and hence the approaches, materials/substrates di er significantly based on applications and requirements. In the recent years, development of electronic circuits and systems on wearable elastomeric substrates has gained a lot of research attentions due to its possible applications in wearable bio-medical devices for clinical diagnostics, electronic-skin for prosthetic implants, artificial-skin for robotics, etc. Traditionally, prob- lems in exible electronics have been handled using two distinct approaches. The former approach involves fabrication of non-crystalline semiconductor based thin film transis- tors (TFTs) and integrated circuits on mechanically exible substrates. This approach is well-suited for applications like large-area displays, image-sensor arrays, etc. How- ever, this approach su ers from several issues like poor mobility, threshold voltage shifts, degradation on exposure to ambience, etc. Hence, this approach is not well-suited for applications requiring high-performance exible electronics with wireless capabilities. The latter approach to exible electronics involves packaging of conventional crystalline semi- conductor based integrated-circuit components on elastomeric substrates. This approach involves heterogeneous integration of rigid circuit components on conformal elastomers using stretchable interconnects, and hence involves addressing issues related to packag- ing and reliability. The usage of conventional electronics based circuit elements helps to build high-speed, wireless systems on elastomers, and hence this approach is well-suited for wearable electronics applications like clinical diagnostic devices. Motivated by such applications, the thesis concentrates on this latter approach of solving packaging...