Which failure mechanism is NOT classified as power-dependent?

Signal degradation is indeed the mechanism that is not classified as power-dependent. This failure mechanism typically involves the deterioration of signal integrity due to factors like interference, attenuation, or other external influences rather than the amount of power being applied to a system. For example, in avionics systems, signal degradation can occur due to environmental factors or the aging of components, which can lead to reduced performance over time.

In contrast, mechanisms like thermal secondary breakdown, metallization melt, and bulk breakdown are influenced directly by power levels. Thermal secondary breakdown occurs when excessive power leads to overheating in a semiconductor, potentially causing failure. Metallization melt refers to the melting of conductors due to high current flowing through a material, which is also power-related. Bulk breakdown relates to the failure of an insulating material when a high electric field is applied, which is directly associated with power. Each of these mechanisms relies heavily on the amount of power involved, distinguishing them from signal degradation.