Environmental Qualification
Accelerated environmental stress testing subjects microelectronic packages and sensor assemblies to continuous exposure at eighty-five degrees Celsius and eighty-five percent relative humidity inside a controlled climate chamber. Under these reference conditions, 85/85 accelerated testing evaluates the long term resistance of polymeric encapsulation materials and die attach adhesives against moisture ingress and thermal degradation over standard exposure intervals of one thousand hours. The procedure stops applying to unsealed hermetic ceramic packages where moisture accumulation does not occur.
Moisture Ingress
Water vapor diffuses through plastic packaging compounds at elevated temperatures, causing interfacial delamination and corrosion of internal aluminum metallization lines. Atmospheric pressure during 85/85 accelerated testing drives moisture along epoxy interfaces toward sensitive die surfaces. Diffusion rates follow Fickian kinetics, accelerating chemical hydrolysis and galvanic oxidation.
Structural Degradation
Hygroscopic swelling creates internal mechanical shear strain between the silicon die and the surrounding mold compound. Prolonged exposure causes microcracks to propagate across wire bonds and adhesive layers. These physical failures lead to open circuits or parameter shifts in sensitive transducer elements.
Metrological Drift
Zero point offset shifts occur when trapped moisture alters the dielectric constant of surrounding materials or exerts mechanical pressure on piezoresistive elements. A sensor subjected to 85/85 accelerated testing undergoes baseline verification before exposure and after thermal stabilization to isolate permanent calibration changes from temporary humidity uptake. Compliance criteria established by JEDEC standards require zero point shift to remain within plus or minus zero point five percent of full scale span.
