Effect of Fixation Method on Solder Joint Vibration Fatigue Reliability of High Density PCB Assembly

In order to explore the influence of various fixation method on vibration fatigue reliability of high density PCB assembly, a three-dimensional simulation model which was almost completely in keeping with test samples was created, and the modal parameters were obtained through modal test and finite element method respectively. Based on the verification of FEM Model correctness, through designed different fixation methods, random vibration finite element simulation was being done, and vibration parameters were picked up and analyzed. The result showed that more PCB fixations could increase the first frequency, decrease the deformation of PCB. Under the same conditions, the order of the first frequency of the PCB Assembly with different fixation methods is: one end fixation <two screws fixation<two ends fixation < four screws fixation < six screws fixation. Consequently, more PCB fixations will decrease stress of key positions of PCB assembly, and BGA (ball grid array) devices should be placed near the region which has more fixation positions. Maximum stress of solder joint is located in the outermost corner of central PBGA module, and the accurate interface of maximum stress is located on the BGA side. And stress increases with the distance between solder and the center of BGA. So, the dimensional structure of PBGA assembly, fixation method of PCB and chip position should be considered comprehensively when vibration reliability of PBGA assembly was analysized. Finally, it can make some references for guiding BGA placement, selecting the appropriate size of BGA and the best fixation method for predicting and optimizing random vibration fatigue life of solder joints.