Resistance Analysis and Fatigue Life of COG Assemblies Under Thermal Cycle Aging

This paper reports the resistance change and fatigue behavior of chip-on-glass (COG) modules undergoing various aging time of cyclic temperature, electric current, and stress by shear fatigue tests. It is noted that as the COG assemblies are exposed in the environment of cyclic temperature, the relative resistance of COG assemblies decreases initially and then increases with the thermal cycling aging time. Moreover, the fatigue life of COG assemblies decreases with an increase of thermal cycling aging time during the shear fatigue tests. The change of relative resistance shows different trends under the different aging time. The relative resistance of COG assemblies having not more than 96 h thermal cycling aging time increases sharply in the initial stage, and then remains at a stable value, and toward the final stage of aging, the relative resistance has a radical change that rises first and then drops. However, when the aging time is not less than 192 h, the relative resistance increases rapidly with increasing fatigue cycles. In contrast, the relative resistance of COG assemblies without aging treatment increases dramatically in the initial stage and is then kept stable, and ultimately surges rapidly. Finally, Miner's damage rules were applied to analyze the damage resulting from the temperature cycling tests, and to obtain empirical correlation between the damage factor and thermal cycling aging time.