Influence of bias humidity testing and application on time-dependent, Arrhenius-law-based stability predictions for thin film resistors

• New model integrates thermal and humidity influences on degradation.
• Replacement of relative humidity by actual vapor pressure as a clear physical date.
• Finding the diffusion properties as the major key for components’ degradations.
• Prognoses in the whole temperature–humidity–time expanse possible.
• Derived ln√t–1/T-diagram contains relevant information of system’s material data.

The time dependence of the drift phenomena in thin film resistors has been shown in a previous paper, which described the conditions in a “dry heat” environment. However, the conditions when using electronic equipment in areas of the world or applications with high relative humidity are still a challenge for component reliability. Therefore, industry standard AEC-Q200 requirements include the biased humidity test 85 °C/85% RH for passive components as well. Qualified thin film resistors are designed with an appropriate stable R-layer and electro-isolation lacquer systems that are capable of passing the 85/85 test.The following questions arise:(1)What does passing the 1000 h biased 85/85 test mean for real world applications of thin film resistors?(2)Is it possible to predict the worst case drifts of resistors under load and environmental conditions over the time of use from the 85/85 or HAST data?To answer these and other test-related questions, an experimental long-time comparison study was made at 40 °C/93% RH and 85 °C/85% RH; the usual standard tests. These were extended to 4000 h at approximately 0.5% and 10% of maximum specified operating power using our most sensitive thin film resistive layer systems. In addition to that, tests at 70 °C/90% RH, 90 °C/40% RH, and HAST130 were performed, enabling a check of the linearity of temperature, humidity, and voltage influence on drift.This paper will show the results of this comparison study, whose data points enabled us to give answers about acceleration factors of applied temperatures and voltages. The results will be compared with available prognosis models. These findings are the basis for the formulation of a new general model covering all aging conditions in the whole temperature–humidity–time expanse, system characterization, and components’ health prognosis.