Flip-chip packages are produced by an interconnection technique in which the active area of a chip is mounted by various interconnecting materials on a multilayer substrate. While flip-chip technologies have progressed rapidly and are now widely used, they present special reliability concerns. A large thermal expansion mismatch between the chip and the substrate increases the likelihood of fatigue failure in solder joints under cyclic thermal loading. In addition, the thermal mismatch often results in the delamination of interfaces between two materials, which eventually leads to mechanical and/or electrical failure. In this paper the use of piezo actuators to mimic stresses during packaging assembly and in operation is discussed. The test has been modeled using finite elements and the results show that the level of stresses reached during packaging can be attained. Electronic speckle-pattern interferometry (ESPI) was applied for noncontact, real-time evaluation of the deformation. Failure analysis has been performed using an FIB dual beam. Cracks extending from the bump edge through the structures under study have been observed.
Phase unwrapping for dual-beam electronic speckle pattern interferometry: method
