Hybrid A/D Converter for 200C Operation

This paper describes the design and development of a high performance hybrid 12 bit analog to digital converter, which will operate reliably at 200°C. A product of this type was found to be necessary in areas such as geothermal probing, oil-well logging, jet engine and nuclear reactor monitoring, and other appl ications where the environments may reach temperatures of up to 200°C. This product represents an advancement in electronics as it proved the operation of integrated circuits at high temperature, as well as providing information about both the electrical and mechanical re1 iabil ity of hybrid circuits at 200°C. Because the circuit design of the A/D converter involved both digital and linear circuitry, this produced an opportunity to evaluate the performance of both technologies at 200°C. Initial mechanical failure modes led to researching more reliable methods of wire bonding and die attachment. The result of this work was a 12 bit A/D converter which will operate at 200°C with .05% linearity, 1% accuracy, 350 ?>Sec conversion time, and only 455mW power consumption. This product also necessitated the development oof a unique three metal system in which aluminum wire bonding is done utilizing aluminum bonding pads, gold wire bonding to all gold areas, and employment of a nickel interface between gold and aluminum connections. This sytem totally eliminates the formation of intermetallics at the bonding interface which can lead to bond failure.