# Modelling the hole-filling of suspensions used in electronics technology by finite volume method

In the first part of my thesis I summarize the suspensions used in electronics technology. Then I present the most important terms related to the properties of the fluids. These are necessary when the parameters of the materials specified. After that I present the paste deposition progresses used in electronics technology such as screen printing or stencil printing and the differences between the two processes.

In the next chapter different mathematic methods like finite elemet, finite volume and finite differential method are introduced which are used by modelling software.

In the end of my literature search I present the fundamentals of the fluid flow in a pipe in steady state when the fluid is homogenous, the Hagen-Poiseuille law, and for transient state the transient Hagen-Poiseuille law, which I use for model as well.

In the second part of my thesis, I present a model to calculate the pressure profile on the surface of the stencil or screen mask. I introduce its geometry, boundary conditions and results. Then I describe non-Newtonian solder paste properties, where the viscosity of the fluid is depending on the shear rate. I use the Cross model to achieve non-Newtonian properties.

After that I introduce the 2-dimensonal axisymmetric geometry of a hole, and the mesh analysis to decide the optimal resolution and structure of the mesh. The first model is steady state, homogeneous and validated by the Hagen-Poiseuille law. The second model is transient and it complies with the transient Hagen-Poiseuille law.

The third model is multiphase and the fluid has non-Newtonian properties. The pressure in the inlet is meets the results of the pressure profile I calculated previously. The hole filling results were compared to experimental hole fill data.

At last, I made calculations for different squeegee speeds and hole diameters to make an expression for calculating the hole filling in different cases.