Thick Film Temperature Compensating Circuit for Semiconductor StrainGauges

Abstract

Thick film circuits were developed for temperature compensating of semiconductor strain gauges and for connecting the gauges to amplifiers in electronic pressure and differential pressure transmitters. In each circuit, ten Au pads for Al wire bonding and thirteen Ag/Pd pads for soldering must be fabricated on a small substrate. The results of the research are shown below.(1) The resistance values and the thermistor constants required for the thermistors are 0.9 ± 0.09 kilo-ohm and 2500 ± 40 Kelvin, respectively. Those characteristics are realized by developing a paste composition composed of a new spinel type oxide (Mn1.6Co0.8Ni0.35Ru0.25O4) RuO2and glass.(2) Accelerated life tests of the thick film thermistors reveal that the resistance drift rates of the thermistors are less than ±0.02 %/year at 120°C.(3) Life tests clarify that the wire bonding pads fabricated by using ESL 8882 Au paste keep more than 4 grams in pull strength, and that the soldering pads fabricated by using Sumitomo CLP 495A Ag/Pd paste are more than 1 kilo-gram in pull strength.(4) The temperature dependence of zero shift and span shift in the pressure transmitter are suppresed within ±0.2% between –40°C and 120°C by using the thick film circuit developed.

Influence of Composition and Construction Parameters on the Basic Properties of Thick Film Thermistors

“…[1][2][3] In order to control the sheet resistivity of TFTs the following modifiers have been tested: RuO 2 1 and Ag. 4 As a much higher degree of TFT stability was found with RuO 2 , this paper presents further information about this system and refers to a number of papers describing the thick film thermistor compositions discussed below.…”