Modeling and characterization for small-scale packaging applications

Ever increasing miniaturization in electronic or electromechanical systems continues to present new challenges in the packaging of small-scale systems. In addition, more stringent design requirements (e.g., lead-free solder) have led to more extensive research on topics such as solder wetting and spreading, capillary flow phenomena, the formation and behavior of intermetallics and the characterization of new and novel coating materials as a few examples.; This dissertation research consists of two parts that are related to the packaging of small-scale systems. The first part of the dissertation research involves the development of three computational models for use in the investigation of solder wetting, spreading and reaction. The second part of the dissertation concerns the characterization of a new type of bilayer coating as a means of protecting small-scale packages, in particular MEMS (MicroElectroMechanical Systems).; Computational models of various complexity have been developed to study wetting, spreading and reaction of solder drop. The hydrodynamic spreading regime is studied using a lubrication theory model, which is applicable to thin drops, in addition to a more complete model based on the commercial finite element package Fidap which was used to solve the full Navier-Stokes equations in a two-dimensional configuration. A drop spreading model which incorporates dissolution of the substrate by the advancing drop is used to investigate the secondary spreading regime. The model treats radial solute transport in an axisymmetric drop with evolving liquid/gas and solid/liquid interfaces. The Gibbs-Thomson condition is applied at the solid/liquid interface. The model yields results for the extent of spreading which are in good agreement with the experimental data. Additionally, the dissolutive model is modified to study the spreading of molten solder on a substrate coated with a thin film. In the final stage of the reactive spreading process, the formation and competitive growth of intermetallic layers in the solid state was studied using a multiphase/multi-layer diffusion model which treats kinetics at the growth interfaces.; The second part of this research concerns the characterization and modeling of a strain-tolerant, protective bilayer coating consisting of an integrated ceramic-organic hybrid material, which is used as a sensible way to tackle the current limitations imposed on MEMS packaging. The microstructure and micromechanics involved in the synthesis and processing of these coatings is systematically studied by a variety of characterization techniques such as XRD, AFM, SEM/EDS and nanoindentation. In addition, the stress field in the bilayer coating is investigated using computational modeling.