Abstract
Fatigue tests on solder joints of surface-mounted type electronic package models were carried out at different temperatures, cycling frequencies and controlled displacement amplitudes in order to examine the crack initiation life Nc, crack extension path, crack extension rate da/dN and crack extension life. The crack initiation life (Nc)cal of solder joints was estimated using maximum equivalent inelastic strain calculated by three-dimensional elasto-inelastic finite element method (3D-FEM). The ratios Nc/(Nc)cal were found 2.4∼9.8. Further, 2D-FEM crack extension analyses were performed to examine crack extension behaviors. The FEM analyses showed that crack extension path and rate were controlled by maximum opening stress range at crack tip, Δσθmax, in plastic zone under rather complicated stress tensor fields. Experimentally obtained crack extension rate was found to be related to Δσθmax in FEM analysis as da/dN=β [Δσ<θmax>]α, with α=2.0 and β=2.65×10-10mm5/N2 being determined independently of the test conditions. The calculated values of crack extension life by the FEM analysis using the above equation were in good agreement with the experimental ones.
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