Measuring the natural convective heat transfer coefficient at the surface of electronic components

Due to increasing power loss densities of electronic components an efficient thermal management is essential to minimize the influence of thermomechanically induced stress and thermal load. Frequently thermal simulation tools are applied to reduce the number of experiments needed for the thermal optimization of semiconductor components. However, a successful application of thermal simulation requires the implementation of well established thermal boundary conditions at the components' surfaces. It is well know that the natural convective heat transfer coefficient strongly depends on the respective surface dimensions. Empirical formulas cited in this context frequently do not suit the dimensions of a typical semiconductor component, since they were established for much larger objects. Accordingly, uncertainties are often related particularly to heat dissipation by natural convention. As a new approach in this work, a measurement procedure and an experimental set-up are presented which allow one to establish the heat transfer coefficient in the regime of natural convection directly at objects with a characteristic length in the range of electronic components. Experiments were carried out at vertical and horizontal surfaces with various form factors to consider their influence on the natural convection. The temperature dependence of the convection coefficients has been established between room temperature and 160/spl deg/C.