Effect of leads pitch on soldered joint reliability of QFP device with finite element analysis

Finite element method was used to simulate the residual stress in soldered joints of QFP device with the same distance and number of leads, respectively.The results indicated that the stress concentration areas in soldered joint locate at the heel and toe of the soldered joint, as well as at the area between the lead and the soldered joint;the largest value of the stress was in the heel of the soldered joints, which would be the weakest area of the joints. Through the comparison of these results, especially the analysis of stress curves, it was shown that stress increased periodically due to the accumulation of residual stress.In the QFP device with the same number of lead, the stress was increasing in the order:TQFP64< VQFP64