Effect of variation in heat flux at leading portion on a PCB subjected to natural convection cooling in air

With the progressive miniaturization in circuit integration technology in the electronic industry, efforts are being made to design and develop printed circuit boards (PCBs) with the ability to mount IC packages that dissipate heat fluxes of higher order of magnitude. It is interesting to study various possible temperature and heat flux distribution at the PCB surfaces. Exploring the effect of one heated zone or portion upon the rest of the board needs intense modeling efforts. In a vertical channel configuration created using a pair of PCBs, subjected to natural convection cooling in air, the effect of variation in heat flux at the a portion of PCB upon the heat fluxes in the down stream PCB zones kept at uniform wall temperature (UWT) is given consideration in the present work. Few relationships based upon scale analysis have been derived for better understanding of trends in distribution of heat flux and surface temperature over UWT and UHF regions respectively. Experimental data for the values of surface heat flux in the down stream region for different fluxes at the upstream zones are presented and compared with the obtained numerical results. Data is useful in evaluating best component layout at the PCB surface in general and, in particular, selecting proper location for a component with given thermal characteristics if a portion of PCB is already populated or being reserved for a particular heat flux load