Micro- and nano-MEMS technology is being increasingly exploited in biological applications, such as large electrode-count neural prosthesis probe arrays. However, a bottleneck in fully utilizing this technology has been the interconnect between the implanted MEMS device and the external system connected to the implanted device. Since the implanted MEMS device is capable of having a large number of elements, the interconnect must have a sufficient number of electrical connections to communicate with each and every element. Complicating this is the fact that the interconnect requirements may include electrical signals, microfluidics transport and optical signals, all packaged in a miniature biocompatible interconnect cable. Micromachined liquid crystal polymer (LCP) is a promising technology for this application, due to LCP's biocompatibility, chemical inertness, electromechanical properties and its ability to be micromachined. This paper presents the results from the development of MEMS packaging technology suitable for use in biological environments, and is demonstrated in the realization of a prototype micromachined LCP biomedical interconnect device. In particular, the development of the interconnect device demonstrates the realization of biocompatible connectors with high-density ultra-fine pitch electrical traces.
Packaging MEMS devices is challenging, especially when the MEMS device is a sensor that requires direct exposure to and simultaneous protection from the operating environment. Because E-glass PCB laminate (FR4) is often used as a substrate for electronic components, a technique for directly integrating MEMS devices onto these substrates at the die level would be useful. This has been accomplished by attaching a bare die HMX2000 MEMS humidity sensor to an FR-4 carrier by forming a Au–Sn eutectic bond between the Au stud bumped die and tin–silver coated landings on the carrier. Prototype devices were then integrated with other electronics and environmentally evaluated. Test results indicated that this packaging technique was reliable.
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