Fiber laser microjoining for novel dissimilar material combinations

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Today's complexity in packaging of MEMS and BioMEMS requires advanced joining techniques that take the specific package integration for each device into account. Current focus on reducing investment and operating costs for device packaging require a flexible and reliable joining approach for similar and dissimilar materials such as metals, polymers, glass and silicon to manage increasing system complexity. Depending on the application, packaged devices must fulfill tough requirements regarding strength, thermal stress, fatigue and hermeticity and long-term stability. This research is focused on laser microjoining of polyimide and PEEK polymers to metals such as nitinol, chromium and titanium using fiber laser. Our earlier investigations have demonstrated the potential of this unique joining technique, which successfully addresses the existing microjoining challenges including high precision, localized processing capability and biocompatibility. Our current study further defines the key processing parameters for joining novel dissimilar material combinations based on the characterization of such laser joints by means of mechanical failure tests and the bond area analysis using optical microscope, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results compare operating windows for generating quality bonds for different material joining configurations. They also provide an initial approach to characterize laser-fabricated microjoints that can be potentially used for the optimization of the design process of devices utilizing these materials. Potential packaging applications include microsystems used for chemical or biological assays (lab-on-a-chip), implantable devices used for pressure or temperature sensing, neural stimulation and drug delivery.