The effects of cross flow mixed convection on discrete mounted heat sources on a circuit board of finite thickness has been analyzed in this study. In this type of flow, the orthogonal free and forced convection result in a three dimensional boundary layer flow. A numerical model is developed to simulate the actual device considering heat generation in the integrated circuit components, conduction of heat through the board and heater modules, and convection of heat from the board and module surfaces to the fluid stream. The significance of the factors that affect heat transfer rate and surface temperatures of these components were analyzed. The equations for the conservation of mass, momentum, and energy were solved in their non-dimensional form to study the velocity and temperature profiles. The numerical model identified important dimensionless parameters such as Richardson number, Prandtl number, source spacing, distance from leading edges, and the ratio of solid-to-fluid thermal conductivities. A parametric study revealed their influences.