Characterization Of Property Degradation Of The Metallic Film Resistors Under Thermal Cycling

Effects of thermal cycling and on the property degradation of the metallic film resistors were investigated by space environment simulators for thermal cycling. The structure and invalidation pattern of the metallic film resistors were analyzed by means of scanning electron microscopy. The composition of metallic film layer and encapsulation layer was studied by the energy spectrometer. The planar finite element mode for the cross section of the metallic film resistors was set up. The thermal stress distribution for the structure layers was analyzed.The experimental results show that the value of the resistor increases with decreasing temperature in cooling stage of thermal cycling. The value of the resistor decreases with increasing temperature in heating stage of thermal cycling. There is a relationship of parabola between the changing rate of the resistor and temperature.There are two stages about effecting of cycles on the changing rate of the resistor. The changing rate of the resistor increases slowly with increasing the cycles which is below the critical value. When the cycles is over the critical value, the changing rate of the resistor increases fast with increasing the cycles, resulting in the resistor invalidation in short time.Some elements are transferred from ceramic and encapsulation layer to the metallic film layer that results in the increasing in the value of the resistor. The thermal mismatch stress among the layers generate damage to the structure, that expressed by forming micro holes in encapsulation layer. When the damage was accumulated to a certainty extent, structural fracture of the layers will occur and result in the invalidation of resistor.The maximal equivalent stress existed in the segment near the interface between metallic film layer and encapsulation layer at up and down limit temperature during thermal cycling, that corresponding with the invalidation pattern of resistors.