Acceleration factors of combined reliability tests of lead-free SnAgCu BGA interconnections

The essence of accelerated reliability test is to accelerate degradation process of tested object and the assessment of its reliability in test and field conditions. Acceleration factor is a unitless parameter that relates a life time of objects at an accelerated stress level to the life time at the use stress level. Acceleration factor of a single loading reliability tests can be calculated on the basis of known models such as Modified Coffin-Manson, Norris-Landsberg or vibration acceleration presented in IPC-SM-785. Acceleration factors of combined tests such as temperature cycle loading combined with vibration loading can not be calculated because such models do not exist. Therefore extensive research are currently carried out. Within the frame of this paper the procedure and the results of the study focused on acceleration factor calculation of combined reliability tests will be presented. Applied method of event detection during accelerated reliability tests and the results of high resolution 3D computed tomography inspections of cracked interconnections will be also presented.