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Moisture absorption and void growing effects on failure of electronic packaging

The purpose of this paper is to study the combined effect of moisture absorption and void growing on the reliability of electronic packaging. Finite element simulation on a plastic PBGA package was carried out for moisture history from the moisture preconditioning (85 degC / 85 % RH for 168 h) to subsequent exposure to a lead-free soldering process, and the rule of moisture diffusion and the change of stress was found. Then, with the implementation of interface properties into the model study, the critical stress that results in the unstable void growth and the delamination at interface is significantly reduced and comparable to the magnitude of vapor pressure. Finite element results give a good guideline on the underfill material selection, and also give an insight of the failure mechanism associated with moisture absorption.