2. Thermomechanical fatigue of brazed joints

2.1 Behavior of electronic assemblies during thermal cycles

The so-called "thermomechanical" fatigue of brazed joints corresponds to LCF (Low Cycle Fatigue) fatigue, characterized by high stress amplitudes and low stress frequencies. This is typically the type of loading encountered during temperature variations. It must be distinguished from polycyclic fatigue or HCF (High Cycle Fatigue), characterized by low stress amplitudes but high stress frequencies, as can be the case for electronic assemblies subjected to vibrations. There is also a VLCF (Very Low Cycle Fatigue) regime, which corresponds to overloads that can occur, for example, during shocks or falls in portable applications. Figure