Hybrid Microcircuitry for 300 Operation

Abstract

Microelectronic instrumentation for geothermal well logging must operate in ambient temperatures up to 300??C for several hundred hours. This study involved an extensive survey of 25 to 300??C operation of resistors, capacitors, conductors, interconnections, and active devices. Three major selection criteria were: 1) part lifetime of at least 1000 h at 300??C; 2) minimum change in electrical parameters from 25 to 300??C; 3) availability to the common circuit builder (no one of a kind). Certain thick film resistors, capacitors, and conductors were found compatible with such high-temperature operation. In addition, reconstituted mica and aluminum solid electrolytic capacitors were found useful up to 300??C. Simple circuits for a geothermal temperature logging tool have been fabricated using these hybrid materials, components, and Si MOS and JFET devices. Oven tests show satisfactory stability from 25 to 300??C and at least 100-h circuit operation at 300??C.