Design and analysis of a novel fine pitch and highly stretchable interconnect Yung-Yu Hsu IMEC-IPSI, Leuven, Belgium and Department of Materials Engineering, K.U. Leuven, Leuven, Belgium Mario Gonzalez IMEC-IPSI, Leuven, Belgium Frederick Bossuyt, Fabrice Axisa and Jan Vanfleteren IMEC-CMST, Gent-Zwijnaarde, Belgium Bart Vandevelde IMEC-IPSI, Leuven, Belgium, and Ingrid de Wolf IMEC-IPSI, Leuven, Belgium and Department of Materials Engineering, K.U. Leuven, Leuven, Belgium Abstract Purpose – The purpose of this paper is to demonstrate electromechanical properties of a new stretchable interconnect design for “fine pitch” applications in stretchable electronics. Design/methodology/approach – A patterned metal interconnect with a zigzag shape is adhered on an elastomeric substrate. In situ home-built electromechanical measurement is carried out by the four-probe technique. Finite element method is used to analyze the deformation behavior of a zigzag shape interconnect under uniaxial tensile loading. Findings – The electrical resistance remains constant until metal breakdown at elongations beyond 40 percent. There is no significant local necking in either the transverse or the thickness direction at the metal breakdown area as shown by both scanning electron microscopy micrographs and resistance measurements. Micrographs and simulation results show that a debonding occurs due to the local twisting of a metal interconnect, out-of- plane peeling, and strain localized at the crest of a zigzag structure. Originality/value – In this paper, the zigzag shape is, for the first time, proven as a promising design for stretchable interconnects, especially for fine pitch applications. Keywords Deformation, Material-deforming processes, Bonding, Films (states of matter), Elastomers Paper type Research paper 1. Introduction Large area deformable macroelectronics, such as flexible display, electronic skin, electronic textile, etc. have to withstand various modes of deformation (e.g. bending, twisting, and stretching). Such electronic systems usually are composed of inorganic parts with limited deformability, and organic parts which can sustain large deformations. Because of the elastic nature of elastomers, these materials are often used as substrates for the specific applications mentioned above. In order to fulfill the demand of deformability, many concepts have been developed. One of these concepts consists of small rigid islands with active devices or individual thin chips which are interconnected by thin metal conductor lines. All rigid components are placed on the small islands to ensure that the strains acting on these brittle components are small when the structure is subjected to a large deformation. Since the thin conductor lines have to withstand all these deformations, a proper structural design is necessary to avoid losing structural integrity and electrical functionality during this deformation. Several technologies have been proposed in recent years, such as in-plane patterned metal conductors (Gray et al., 2004; Brosteaux et al., 2007; Li et al., 2005), out-of-plane wrinkling metal films (Mei et al., 2007; Lacour et al., 2003), and conductive polymers or liquid alloys (Deshpande et al., 2005; Kim et al., 2008). It has been reported that by depositing a thin metal strip with a thickness of few nanometers on an elastomeric substrate, the elongation of the metal can go up to 50 percent while the strip remains The current issue and full text archive of this journal is available at www.emeraldinsight.com/1356-5362.htm Microelectronics International 27/1 (2010) 33–38 q Emerald Group Publishing Limited [ISSN 1356-5362] [DOI 10.1108/13565361011009504] This paper is supported by European Commission, under the research project of STELLA (Contract Number 028026). The authors would like to thank Frederic Duflos and Veerle Simons for their support of equipment setup and experiment. 33