Effect of circuit board parameters on thermal performance of electronic components in natural convection cooling

Natural convection is the most desirable cooling mechanism for electronic enclosures. Limited cooling capacity with natural convection requires identification and optimization of parameters impacting cooling. A set of such parameters is circuit pack layout and board conductivity (circuit board parameters). Hence, experimental and numerical simulations were undertaken to investigate the impact of these parameters on thermal performance of an electronic component in circuit pack setting. Component thermal performance was characterized by its junction to ambient thermal resistance (R_ja), where room ambient was used as the reference temperature. The numerical model was verified against the experimental data with 4 percent agreement between the two analyses. The numerical model was then expanded to include the circuit board parameters. The effects of the spacing and height of the neighboring components, and board conductivity on thermal resistance were investigated. The model consisted of an array of nine components (3×3), with the center component as the focus of the study. Three values for board conductivity, component spacing and neighboring component height were considered. The data showed that increasing k_board three folds resulted in 17 percent reduction in R_ja. Similarly, a three fold increase in component spacing reduced the R_ja by 24 percent. It is deduced that the least junction to ambient thermal resistance was attained when component spacing was 0.023 m (900 mils) and board conductivity was 13.6 W/m°K