Gas flow simulations in convection reflow ovens

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Supervisor:
Dr. Illés Balázs György
Department of Electronics Technology

With the spread of Surface Mount Technology reflow soldering has become the most commonly used bonding technology in the electronics industry. The heating solutions of reflow ovens have evolved a lot over the years. The gas flow conditions in convection reflow ovens fundamentally influence the quality of the soldering. Computational Fluid Dynamics (CFD) methods provide a solution to simulate the gas flow.

In my thesis I present the research of literature in the subject: the types and structures of reflow ovens, overview of the physical processes taking place in them (heat transport, gas flow), introducing the basics of CFD methods.

Acquiring the theoretical foundations was essential to construct a simplified two-dimensional CFD model of the heating zone of an oven with nozzle-matrix structure. The calculation was performed in Ansys Fluent software, which offers professional solutions for solving fluid dynamics problems.

I have chosen two orthogonal sections of the oven to construct the two-dimensional models. First, the longitudinal model was examined using laminar flow model, but the result was not as expected because it was not able to properly handle the turbulences beside the major laminar flow. For the further simulations therefore I used the standard k-ε turbulent flow model, which resulted in a flow pattern corresponding to expectations. The cross-sectional model resulted in a different flow pattern due to the lack of outputs, so I have performed the tests with board and components in both models.

The two-dimensional results were compared with the corresponding sections of a three-dimensional model. Similar flow pattern was obtained, but differences in velocity vector magnitudes were observed. For simpler tests the 2D model can be used instead of the 3D model in order to reduce the computational complexity.

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