Cardiovascular diseases and neurological disorders form the majority of diseases that need periodic or constant medical attention. Such continuous monitoring requires non-invasive and imperceptible device to prevent a lack of comfort that would impede continuous wearing. For this reason, smart textiles are currently being considered as a relevant solution. Specific reliability issues related to strain during wearing and washing have to be addressed.
In this work, we focus on the mechanical reliability of fundamental surface mounted devices (such as passives components and microprocessor) on flexible polymeric substrates embedded onto textile. We developed a specific experimental protocol in order to characterize the radius of curvature of the overall bent system down to few hundreds micrometers through optical measurements. At the same time, in-situ electrical characterizations are correlated to mechanical cycling in order to determine the reliability of the device.
This study investigates the mechanical behavior of the electrical interconnection between electronic components and conductive tracks. Different elastic conductive materials are investigated and compared to standard electronic processes (i.e., tin-based alloys soldering, flip-chip). The study also points out the influence of the stack composition in multilayer electronic systems on the overall reliability of the device. The combination of optimized stack layout and compliant interconnections allow the fabrication of robust and ultra-thin devices for a comfortable and continuous monitoring.