Failure of polymer-metal interfaces under hygrothermal loading

This paper describes a study of the failure of polymer-metal interfaces in plastic-encapsulated IC packages subjected to hygro-thermal loading during solder reflow. All the analyses performed are under plane strain conditions. A finite element fracture mechanics approach was employed to predict the temperature at which a small delamination in the polymer-metal interface of an IC package will propagate. In order to confirm the accuracy of the above prediction, actual package specimens were fabricated and subjected to various levels of moisture preconditioning followed by thermal loading at varying temperatures. The specimens were then examined to determine the temperature at which the interface failed. Good agreement was found between numerical prediction and experiment.