Modelling and Reliability Assessment of Microsystem Interconnections
Doctoral thesis, 2007
With the continuous increase of packaging density, the electronic component size and, in particular, the thickness of the involved interconnections decrease significantly. In addition, the microsystem interconnects usually include even finer internal structures. The wide range of size differences is a challenge for the in-depth analysis of the reliability of such components. To this end, an interface model has been developed based on micropolar theory, including the concept of regularized strong discontinuity in order to model the interconnections considered as an interface of finite thickness. A second order homogenization strategy has been adopted in the model development, including a Taylor expansion of the displacement field to describe the coupling of the mechanical macro- and micro-responses. The involved representative volume element (RVE) has been chosen according to a typical structure in the adhesive interface. Thereby, the internal length and material parameters of the microstructure of the interconnect are involved in the macroscopic constitutive equations. The multi-scale character of the interconnect problems, such as in anisotropic conductive adhesive (ACA) interconnects, plays an important role in the proper stress-strain analysis. For model verification, the deformation fields of the plastic ball grid array (PBGA) component joints under thermal loading have been observed by a 4M interferometer. The comparison between the micropolar model simulation and experimental data shows a good agreement. Finally, a delamination model has been developed for the interconnect degeneration. A cohesive zone model is included to describe the failure process. The crack initiation and propagation of an anisotropic conductive film (ACF) microstructure under thermal cycling has been simulated, and reliability analysis has been made.
cohesive zone model