High temperature electronics are needed for geothermal well logging tools. This report summarizes a survey of materials and passive components required for high temperature printed circuit boards and thick film hybrid circuits. Com¬mercially available resistors, capacitors, substrates, conduc¬tors, and bonding techniques were tested over the temperature range of 25-300°C. Thick film resistors were found to have a total change in resistance of 1-5% from 25-300°C, and a resistance drift of less than 1 percent during 1000 hours at 300°C. Several types of capacitors were found that showed total capacitance change from 25 to 300°C of about 5 percent, high temperature dissipation factors of less than 10 percent, 300°C insulation resistances of 10 megohm-microfarad, and high temperature lifetimes greater than 1000 hours. Polyimide board with Ni plated Cu cladding, and alumina ceramic with thick film Pt-Au conductor paths were shown to be suitable for high temperature microcircuit frameworks.
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