The Development of Precision Thin Film Resistors for Submerged Repeater Applications

Abstract

The paper describes development of a low inductance thin film resistor series with a stability of ±0.15% change in resistance, over a 25 year life, in a submerged repeater environment. (40% RH maximum and 0 to 30℃ ambient temperature).It was first necessary to establish an appropriate mathematical model relating resistor stability with time and temperature. This was devised from experimental data based on measured resistor drift at various temperatures, and enabled acceleration of resistor drift to be carried out to ensure that each resistor possessed the required stability.Deposition of a secondary nichrome layer protects the gold/nichrome interface and promotes SiO2adhesion. This results in an improvement in the basic elevated temperature resistor stability by minimising diffusion effects of nichrome into the conductor, and protection against electrochemical corrosion as demonstrated by 10,000 hours life test at 83% RH @ 28℃ on 5 mW load and by elevated temperature tests under electrical loading.