Lifetime prediction of solder materials

Fatigue lifetimes of lead-low tin solders have been investigated. Results indicate that the Coffin-Manson law does not necessarily fit experimental data. The phenomenon can be correlated with a change in the failure mode as follows: transgranular and mixed for higher strain ranges, and intergranular at lower strains. The present modeling incorporates these micromechanical features, and in addition shows that the variation in the failure mode and in the magnitude of the stresses from varying strain range (during the cyclic process) coincide with each other.