Abstract
Methods of accelerating the ageing of thick-film resistors (TFRs) have been explored, with encouraging results from experiments in which elevated temperature and damp heat were inflicted on TFRs. Consistent acceleration was obtained by increasing temperature, whether by storage or dissipation, the activation energies for thermal ageing of various resistor families lying in the range 0.5 eV–1.5 eV. Acceleration by humidity (RH) was also obtained, corresponding, for example, to a halving of life for a 20% increase of RH, some resistance changes being about an order of magnitude larger than those obtained at elevated temperature. The encapsulations played a dominant role in the degradation of resistors under both stress conditions.According to the theories of conduction, degradation could occur because of reactions at conductive sites, causing corresponding changes in the conductivity and resistance versus temperature (R(T)) characteristics. Progressive degradation certainly did occur, as evidenced by the conformity of the ageing behaviour to a diffusion-type (time)1/2 dependence accompanied by shifts in the R(T) characteristics. Some interpretation of the degradation has been possible by referring to an empirical model of the temperature dependence of resistance, but conflicting changes can be reconciled with the model only by postulating competing degradation mechanisms. The report covers an early stage of the work.