A User´s Performance Profile of a Thick-Film Resistor System

The DuPont Birox¹1400 resistor system has been successfully used by Sylvania for several years. However, only recently has it become practical to meaningfully track the performance on a production lot basis by using a data acquisition system centered on an HP 9825 calculator. During a 39-week period in 1977-1978, 30 production lots of 11 types of custom precise resistor networks involving 1 836 503 thick-film resistors were processed. The overall process is described and detailed. The screen-printed materials utilized were DuPont 9791 gold, DuPont resistor decades (100 / through 1 M / , DuPont 9770 platinum silver, DuPont 8185 glaze, and ESL 240 SB polymer encapsulant. The process steps were printing and firing followed by laser trimming, polymer encapsulation, lead attaching, solder dipping, and testing. The testing followed MIL-R-83401A requirements for class M resistor networks. Thus every production lot was statistically sampled and subjected to thermal shock and power conditioning tests as detailed by MIL-STD-105 and MIL-STD-202 specifications. The tests and comparisons were performed by the HP 9825 test system which is described. Routine GO/NO GO tests were performed to satisfy the test requirements, but in addition data files were stored. These data files were subsequently accessed by software to provide statistical comparisons of the resistor distributions involving histograms resulting in a baseline reference to determine the potential yields. Furthermore, by using representative resistors, meaningful comparisons were made of the resistor distributions before and after thermal shock and power conditioning resulting in a stability baseline. As a consequence correlations of these yield and stability characteristics were made with the measured production lot variables of laser trim parameters, firing profile, glaze thickness, as-fired values, and resistor print thickness. Based upon the effects of the above variables upon the DuPont resistor system, an assessment was made of both the overall stability potential inherent in the material and the actual practical realization as obtained by the Sylvania process.