Finite element analysis on soldered joint reliability of QFP device with different lead materials

Finite element method was used to simulate the residual stress in soldered joints of QFP device with three kinds of lead materials.The results indicate that all the stress concentration area in soldered joint is at the sharp corner of interior part of the joint where is the weakest area of the joint.Comparing with the simulating results about alloy-42, copper alloy and Kovar alloy, especially analyzing the nephograms of equivalent strain and the strain and stress curves, it is shown that the stress and strain makes periodic change with the time, simultaneously has the accumulated tendency, and the value of strain and stress in the soldered joint of alloy- 42 gull is the least, and the value is middle in the joint of Kovar alloy, and the value was largest in the joint of copper alloy.The simulating results may provide a theory guide for developing novel lead material as well as selecting lead materials in production.