High temperature MEMS packages: die-attach solutions for LiNbO3 under low bonding pressures
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A survey of high temperature die-attach solutions for lithium niobate (LiNbO3) single crystals was conducted and based on that three promising approaches; i.e. eutectic solder, silver sinter-paste and silver-loaded conductive adhesive; were proposed and investigated. A relatively low pressure span (0–4 MPa) was employed, aiming to mitigate the risk of fracture in the brittle die. The mechanical properties of the corresponding die-attach assemblies was examined by a die-shear tester and the reliability of the joints was assessed after isothermal aging at 300 °C. The micro-structural integrity of the bonding was also analyzed by cross-sectional microscopy. The results revealed that silver sinter paste die-attach possesses superior shear strength in comparison to the two other techniques. Cross-sectional failure analysis also indicated a ductile fracture mode throughout the bonding layer for silver-paste and adhesive joints, whereas in soldered assemblies a brittle fracture mode along the interfacial intermetallic compound layer was predominant.
KeywordsShear Strength Lithium Niobate Conductive Adhesive Eutectic Solder Lithium Niobate
This project has been supported by the COMET K1 center ASSIC (Austrian Smart Systems Integration Research Center). The COMET (Competence Centers for Excellent Technologies) Program is supported by BMVIT, BMWFW and the federal provinces of Carinthia and Styria. SEM investigations were carried out using the facilities at the University Service Center for Transmission Electron Microscopy at the Vienna University of Technology.
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