One of the major engineering interest in second level packaging of electric system is the failure by a thermally induced stress. However, the electronic system often experiences the vibration in use, and therefor to assure the high product reliability, it is necessary to estimate the fatigue life in the random vibration environment.
For this purpose, High cycle fatigue tests are performed under a constant amplitude loading and a random loading for the solder bump. The test machine utilizes the electromagnetic force as an actuator, and personal computer was used for force signal generation and data acquisition. The specimen used in this experiment is a BGA-type solder-printed circuit board (PCB). To introduce the stress in the solder bump, The PCB is subjected to a torsion with a 40 Hz frequency. The fatigue life is determined by a change of an electrical resistance in the solder bump. Using ABAQUS, the stress and total equivalent strain in the solder bump was calculated to determine the coefficients of the coffin-manson type fatigue life. The random force signal was calculated from a computer simulation with power spectrum and fatigue life of solder bump under random vibration is estimated by the rainflow cycle counting and linear damage rule.
