During my diploma thesis design, I studied the condensation heat transfer phenomenon, during vapor phase soldering. Vapor phase soldering is a reflow soldering method, recently renewed due to the problems caused by lead-free soldering. Due to its advantages, it is a good alternative solution against convection based ovens, thus it is important to study the process. The goal is to calculate the exact value of the heat transfer coefficient, from thermal profiles measured on test boards, which is defined by Newton’s law of heat transfer.
As a first step, in the part of literature research, I studied the physics of condensation heat transfer, and it’s modeling possibilities on differently oriented plates, based on the Nusselt theory. I also learned about the temperature measurement methods, using thermocouples, as well as the way to calculate the heat transfer coefficient from the temperature data. In my thesis, I summarized the results of the research.
Furthermore, I have designed a measuring method, using the available thermocouples and data recorders. By defining the measuring arrangement, there were two main aspects considered: the thermal profile must be known in the largest number of points on the plate surface, but the layout must have a minimal effect on the flow and therefore on the heat transfer itself. With the designed arrangement, thermal profiles were successfully measured on two square and two circle shaped FR4 test boards.
The measured data, after interpolation, were displayed on three-dimensional figures, as well as the calculated heat transfer coefficient values. Based on the graphical analysis of the figures it can be stated, that the heat transfer is not completely homogeneous on the surface of the board, it increases at the edges of the test boards, which verifies the theory of condensation on horizontal boards.