Laser based fast prototyping methodology of producing stretchable and conformable electronic systems

For user comfort and reliability reasons, electronic circuits for human body related applications should ideally be soft, elastic and stretchable, for smart textile application, but also for applications which need a high level of biocompatibility. We are developing several roll-to roll technologies using MID (Molded Interconnect Device) and low cost standard PCB technology (Printed Circuit Board) to produce soft, stretchable, human-compatible packaging. All those technologies are based on a sacrificial layer on where meander shaped interconnections are patterned. Those stretchable interconnections are connecting together non-stretchable functional islands on where SMD components are soldered. All the system is then embedded in stretchable polymer matrix, silicone rubber or polyurethane. All these technologies are using standards methodologies for PCB productions (lamination, photolithography, copper etching, reflow oven lead free soldering). A fast prototyping technology has been developed to ease the development of stretchable electronic circuits. Less than 1 day is necessary from CAD design to finalization: Rigid or flexible standard components or electronic sub-systems are interconnected with YAG laser shaped meander interconnections and molded in silicone rubber afterwards. From any kind of flexible circuit, stretchable circuit can be produced using this methodology. The stretchable meander interconnection can be stretched more than 100% and can sustain at least 3000 cycles at 20% of deformation. This paper presents a general overview of stretchable electronic process, a detailed view of the fast prototyping technology using YAG laser cutting, and the demonstrators developed in the frame of the European project STELLA (Stretchable Electronic for large area) [7] and in the Belgian project SWEET (Stretchable and washable electronic in textile) [8] and BIOFLEX (Biocompatible stretchable electronic system) [9].