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Low temperature transient liquid phase bonding of Au/Sn and Cu/Sn electroplated material systems for MEMS wafer-level packaging

: Marauska, S.; Claus, M.; Lisec, T.; Wagner, B.


Microsystem Technologies 19 (2013), No.8, pp.1119-1130
ISSN: 0946-7076
Journal Article
Fraunhofer ISIT ()

This paper presents the development of a low temperature transient liquid phase bonding process for 8 wafer-level packaging of micro-electro-mechanical systems. Cu/Sn and Au/Sn material systems have been investigated under varying bonding temperatures from 240 to 280 °C and different dwell times from 8 to 30 min. The used bond frame had a width of 80 m and lateral dimensions of 1.5 mm × 1.55 mm. The sealing frame of the cap wafer consisted of Au and Cu, respectively, and Sn. The MEMS wafer only holds the parent metal of Au or Cu. High quality bonds were confirmed by shear tests, cleavage analysis, polished cross-section analysis using optical and electron microscope, energy dispersive X-ray spectroscopy and pressure cocker test. The samples showed high shear strength (>80 MPa), nearly perfect bond regions and no main failure mode in the cleavage analyses. Non-corroded Cu test structures confirmed the hermeticity.