Thick Film Packaging Techniques for 300°C Operation

Abstract

Geothermal well logging and instrumentation applications require electronics capable of 300°C operation. SiC device technology enables the design and fabrication of analog circuits that can operate at these temperatures. However, to build functional systems operating at high temperatures, an interconnection and packaging technology must be developed to provide interconnectivity between different SiC devices and passive components. Key elements of a high temperature packaging technology include the interconnection substrate, die attach and wire bonding. New developments in each of these areas for high temperature operation are discussed in this work. Thick film technology based on ceramics and metals has potential for higher operating temperatures. In this work, the effect of 300°C storage on the adhesion of different thick film conductors and multilayer dielectrics has been studied. In addition, the electrical properties of the dielectric, including leakage current, capacitance, and dissipation factor, have been studied as a function of temperature and of high temperature aging. The leakage current was also investigated as a function of high temperature aging under DC bias voltage. Eutectic AuSn die attach was used with a Ti/TiW/Au backside die metallization for 300°C operation. Liquid Phase Transient (LPT) die attach process was developed. Results of die attach reliability based on shear strength were discussed after thermal storage and thermal cycling tests. Investigation of Au wire bonding on different SiC die metallization was reported. Failure analysis after reliability testing was also performed. Passive components were selected for this high temperature application and an attach process was developed. After an initial test, one resistor and one capacitor were selected for reliability testing after 300°C storage and thermal cycling tests. External lead attach was also investigated for next level device connection. Before building the final amplifier module, a SiC die was attached in a ceramic DIP package and tested functional at 300°C. An amplifier module was fabricated on a multilayer thick film ceramic substrate. Passive components and the SiC chip were then assembled. The amplifier was tested as-built and after high temperature storage.