B3.1 - Assembly and Interconnection Technologies for Sensors for Very High Temperature Applications

Abstract

This work aims at the development of technologies to assemble, interconnect and protect sensor elements operating in harsh environments up to 500 °C. Silicon test-chips were mounted on substrates made of Al2O3, AlN and Si3N4 to examine their influence on the sensor. Active metal brazing, glass soldering and ceramic bonding were used as mounting technologies. The stress induced in the chip by the die attachment process was analyzed by optical deformation measurements of the chips as well as by FEM-simulations and by resistance measurements. The mechanical stability of the assemblies was tested with shear-tests before and after 100 hours storage at 500 °C. In our study the glass-soldering process on an AlN substrate appeared to be the most suited technology when the reliability of SiC-MEMS is the principal criterion. In a second step an interconnection technique based on fine wire bonding was developed. When metallurgical systems consisting of Pt or Pd are used for the metallization and the wires, these interconnect systems can be stable. Up to date, we could verify the stability after temperature soak at 500 °C and during operation at 300 °C. Fig. 1 Pressure sensor in the combustion chamber of a Diesel engine. Image courtesy of Robert Bosch GmbH. Fig 2 Thin film test sensor assembled with temperature stable technologies up to 600 °C