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Proceedings Paper

System integration of the Utah electrode array using a biocompatible flip chip under bump metallization scheme
Author(s): Rajmohan Bhandari; Sandeep Negi; Loren Rieth; Michael Toepper; Sohee Kim; Matthias Klein; Hermann Oppermann; Richard A. Normann; Florian Solzbacher
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Paper Abstract

The advent of micro and nanotechnologies along with integrated circuit technologies has led to many exciting solutions in medical field. One of the major applications of microsystems is microelectrodes interfacing neurons for large scale in vivo sensing, deep brain stimulation and recording. For biomedical microsystems, material selection is a challenge because biocompatibility has to be considered for implantable electronic devices. We are using flip chip bonding to integrate a signal processing IC to the Utah electrode array (UEA). Conventionally the flip chip process is used to bond a die to a substrate or interposer. In this work the electrical interconnects are made from the under bump metallization (UBM) on the UEA to the solder bumps on the IC. The UBM selection and reliability is one of the critical issues in the total reliability of a flip chip bumping and interconnection technology. The UBM was optimized to achieve improved interconnect strength, and its reliability was evaluated by conducting solder ball shear strength testing. The UBM reliability was tested with two solder metallurgies including AuSn and SnCu0.7. These solders are needed to allow two reflow processes to be used, an initial higher temperature (350 °C) and a second lower temperature process (250 °C).

Paper Details

Date Published: 27 April 2007
PDF: 8 pages
Proc. SPIE 6525, Active and Passive Smart Structures and Integrated Systems 2007, 65251K (27 April 2007); doi: 10.1117/12.716102
Show Author Affiliations
Rajmohan Bhandari, Univ. of Utah (United States)
Sandeep Negi, Univ. of Utah (United States)
Loren Rieth, Univ. of Utah (United States)
Michael Toepper, Fraunhofer Institute for Reliability and Micro Integration IZM (Germany)
Sohee Kim, Univ. of Utah (United States)
Matthias Klein, Fraunhofer Institute for Reliability and Micro Integration IZM (Germany)
Hermann Oppermann, Fraunhofer Institute for Reliability and Micro Integration IZM (Germany)
Richard A. Normann, Univ. of Utah (United States)
Florian Solzbacher, Univ. of Utah (United States)

Published in SPIE Proceedings Vol. 6525:
Active and Passive Smart Structures and Integrated Systems 2007
Yuji Matsuzaki; Mehdi Ahmadian; Donald J. Leo, Editor(s)

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