Electromigration in flip-chip solder joints

With the portable devices becoming smaller and more compact in size, flip-chip technology has been adopted for fine-pitch packaging in microelectronics industry. Area array of tiny solder joints can be fabricated on Si chips to achieve high-density packaging. In addition, as the required performance continues to increase, the input/output (I/O) pin count of flip-chip products has dramatically increased and the current that each bump needs to carry continues to increase, resulting in higher current density flowing in each solder bump. Therefore, electromigration (EM) has become an important reliability issue in solder joints. It has been reported that serious current crowding and Joule heating are responsible for the failure mechanism. In this talk, role of current crowding and Joule heating on void formation and propagation will be presented. Furthermore, the methods for relieving current crowding and Joule heating will be discussed to prolong electromigration lifetime