Abstract: The main external factor of solder joints degradation or deviation from an expected normal condition is the time stress such as work and environment stresses. A damage assessment method for solder joints based on time stress monitoring and three-dimensional finite element model is introduced. A damage-fault evolution model of solder joints based on hidden Markov models (HMM) is put forward. And then, the fault prognosis technology of the solder joints is researched based on the HMM model, real-time damage information and life consumption prognosis method. The detailed process and algorithm of the fault prognosis technology are studied based on time stress monitoring. Finally, the validity of the technology is proved by an experimental study of plastic quad flat package (PQFP) solder joints.

Key words: Fault prognosis, Hidden Markov models (HMM), Solder joints, Time stress, alloy powder, laser cladding , path planning , 3D scanning , rail abrasion