“Microflex”—A New Assembling Technique for Interconnects

A new interconnection technique has been developed that allows versatile multiple strand connections between microsensors, sensor arrays, and chips designed for wire bonding. The new technique has been termed “Microflex interconnection” technique (MFI). Conventional wire bonding technique is commonly restricted to planar interconnects with a limited degree of freedom for placing microsystem components in hybrid assemblies. The MFI technique has overcome this limitation by interconnecting microsystem components through custom designed flexible substrates with embedded metallized conductors, pad arrays for integrated circuits’ assembly and substrate integrated electrodes. Standard CMOS components without additional pad metallization can be used. The integration density of the MFI technique corresponds to one of the flip-chip technology. Special advantages of the MFI technique are three-dimensional interconnects, the flexibility in design and shape, and easy visual inspection of alignment qualities. The method is especially suitable for small volumes of customer specified devices and biomedical implants because all materials used are biocompatible. Within this paper, the MFI technique is introduced, described in detail, and tested according to international standards. The evaluation of the electrical and mechanical properties of the interconnection sites exhibited promising results regarding stability and reliability. First applications in the biomedical field were presented on the example of a neural implant and a sensorized cardiac catheter.