The work developed in this thesis is inserted in a large project involving the University of Minho and the Bosch Car Multimedia, in which it is intended to create a numerical model capable of simulate the Reflow soldering process. Thus, during this thesis will be given a small contribution to the creation of this model by continuing the work already developed by Costa (2014), student who initiated this project in his master's thesis. Before starting the development of the simulation model, it is performed a brief description of the electronic products manufacturing process and its composition, such as PCBs, electronic components and solders used. Being even discussed in greater detail the Reflow soldering process. To carry out this simulation model it is used the computational program ANSYS Fluent being analyzed its way of functioning and the main models used during the simulations, as the VOF model (Volume of Fluid) and the Solidification/Melting model. Regarding the development of the simulation model, the first step passed by the analysis of the work carried out by Costa (2014), which it resulted in detection of a problem in his last model, related to the deformation of solder paste at room temperature. In an attempt to prevent this deformation several variables were analyzed such, as density, viscosity and surface tension of solder paste, as well as the presence of gravity and the Mushy-zone parameter in order to understand their impact on the solder paste deformation at room temperature. Through this analysis, it was found a solution which involves the alteration of Mushy-zone parameter and the use of a surface tension of solder paste function of temperature. With this solution it was possible to create a model for the fusion of solder paste, with the objective to validate the solution found and to analyze the deformation of solder paste. Finally, it developed a simulation model that allows to simulate any Reflow thermal cycle and to analyze the deformation of solder paste during the entire thermal cycle, including its melting and solidification. In parallel with this project, it was accomplished at Bosch the thermal simulation of the Reflow soldering process of a real product and compared the values obtained with the actual data from the production line.