Computational models for microvia fill process control

The microvia fill process is an electrochemical copper deposition process applied in the manufacturing of multilayered printed circuit boards (PCBs). It is the process where the metallic interconnections between adjacent signal layers of the multilayered PCB are made. The process chemistry is complex, including the interactions of several additive chemicals in addition to the underlying basic electrochemical processes of copper electrodeposition. To this day, the microvia fill process equipment set-ups utilized in the industry have none or very little automatic online control of the process variables. This is mostly because direct online measuring of the microvia fill process is practically impossible due to the vast number of microscopic features on a PCB, as well as to the small size of the features. The electronics industry is continuously striving to produce cheaper, smaller and more complex devices for an immeasurable number of applications. In the core of every electronics-appliance there is a PCB, which forms the chassis for the electronic components of the device as well as the signal paths between the components. Considering the enormous size of the electronics industry, as well as the ubiquitous nature of electronics, it is clear why PCB manufacturers consider that improving the microvia fill process technology is a relevant object for development. This doctoral thesis presents novel means for improving the microvia fill process through process simulation and model-based process design. The main results of the thesis are distributed parameter models, which together form the main components necessary for modeling a practical microvia fill electrolysis apparatus and designing a model-based control system for the process. Though the models are primarily based on physical and chemical first principles, the development work of all models presented in this thesis relies on experimental data that is gathered to parameterize and to validate the models. The thesis consists of a summary and nine publications, which address the modeling of the microvia fill process, the computational methods necessary for these models and the modeling of copper electrolysis systems in general.