Rožňava ore field - geophysical works

The article prowides a review of geophysical works in the ore field Rožňava conducted up to date. Magnetometric and geoelectric methods and gravimetric measurements have been used. Geophysical works were focused to the solving regional problems whose contribution to the prospecting of vein deposits is not essential

Numerical Simulation of Condensate Layer Formation During Vapour Phase Soldering

This paper presents a modeling approach of the condensate layer formation on the surface of printed circuit boards during Vapour Phase Soldering (VPS) process. The condensate layer formation model is an extension to a previously developed board level condensation model, which calculates the mass of the condensed material on the surface of the soldered printed circuit board. The condensate layer formation model applies combined transport mechanisms including convective mass transport due to the hydrostatic pressure difference in the layer and the gravity force; conductive and convective energy transport. The model can describe the dynamic formation and change of the condensate layer after the immersion of the soldered assembly into the saturated vapour space and can calculate the mass and energy transport in the formed condensate layer. This way the effect of the condensate layer changes on the heating of the soldered assembly can be investigated. It was shown that the numerical modeling of the VPS process becomes more accurate with application of dynamic condensate layer instead of a static description

Modeling Method of Heat Transfer During Vapour Phase Soldering Based on Filmwise Condensation Theory

The paper presents a practical method for calculating the heat transfer during Vapour Phase Soldering (VPS) process. VPS is a reflow soldering method based on condensation heating and used in the electronics manufacturing. The presented explicit model describes solutions for filmwise condensation heat transfer based on the Nusselt theory. Different approaches on describing the filmwise condensation were investigated, compared and modified in order to determine a proper heat transfer coefficient for the VPS process - where the heated assembly can be considered as a horizontal plate. For the verification, measurements were done in an experimental soldering oven. The results of the calculations show a proper approximation with the measured temperature data. Finally the results were compared with a solution obtained from complex multi-physics simulation. The results point out, that the application of filmwise condensation model for VPS can be more practical than a complex multi-physics model, from the aspect of calculation error and computation time