A New Low Cost, Elastic and Conformable Electronics Technology for Soft and Stretchable Electronic Devices by use of a Stretchable Substrate F. Bossuyt, T. Vervust, F. Axisa and J. Vanfleteren CMST, University of Ghent, Technologiepark 914A, 9052 Zwijnaarde Phone: +32 (0) 9 264 53 54, Fax: +32 (0) 9 264 53 74 and Frederick.Bossuyt@elis.ugent.be Abstract A growing need for ambient electronics in our daily life leads to higher demands from the user in the view of comfort of the electronic devices. Those devices should become invisible to the user, especially when they are embedded in clothes (e.g. in smart textiles). They should be soft, conformable and to a certain degree stretchable. Electronics for implantation on the other hand should ideally be soft and conformable in relation to the body tissue, in order to minimize the rejecting nature of the body to unknown implanted rigid objects. Conformable and elastic circuitry is an emerging topic in the electronics and packaging domain. In this contribution a new low cost, elastic and stretchable electronic device technology will be presented, based on the use of a stretchable substrate. The process steps used are standard PCB fabrication processes, resulting in a fast technology transfer to the industry. This new developed technology is based on the combination of rigid standard SMD components which are connected with 2-D spring-shaped metallic interconnections. Embedding is done by moulding the electronic device in a stretchable polymer. The reliability of the overall system is improved by varying the thickness of the embedding polymer, wherever the presence and type of components requires to. Manufacturability issues are discussed together with the need for good reliability of the stretchable interconnections when stress is applied during stretching. Key words: Ambient electronics, biomedical electronic implants, moulding, PDMS, polymers, smart textiles, stretchable electronics, stretchable interconnections I. Introduction Stretchable, elastic electronic interconnection technologies will be a major improvement in the development of biomedical implantable electronics and smart textiles. User comfort expressed in softness and elasticity of the electronic device is a major issue. Our main philosophy of stretchable electronic devices is that standard SMD electronic components are used, typically being non-stretchable. They are grouped in non-stretchable functional islands. To make stretchability happen, the different islands are connected by 2-D spring-shaped copper connections. This principle is shown in Figure 1. Copper connectors are preferred above conductive polymers, due to their high conductivity, reliability and low cost. Some research groups [1]- [6] reported already their activities on the development of stretchable metallic interconnections on or in elastic, stretchable substrates. In [7,8,9] our technology based on plating gold meanders was presented together with optimizations of stretchability by use of finite element analysis (FEA) to obtain the optimal shape of the conductor shape. The shape of the copper conductors used in this paper is based on these results. II. Method In [7-14] a technology based on plating gold metal tracks on copper foil was presented. This approach has some major disadvantages. While Figure 1: Stretchable electronics’ architecture principle