Experimental and numerical investigation into the influence ofprinted circuit board construction on component operating temperature innatural convection

The steady state thermal performance of an isolated SO-8 package is experimentally characterized on five thermal test printed circuit boards (PCBs) and the results compared against corresponding numerical predictions. The study includes the low and high conductivity JEDEC standard, FR4 test PCBs and typical application boards. With each PCB displaying a different internal structure and effective thermal conductivity, this study highlights the sensitivity of component operating temperature to the PCB, provides benchmark data for validating PCB numerical modeling methodologies, and helps one assess the applicability of standard junction-to-ambient thermal resistance (&thetas;_JA) data for design purposes on nonstandard PCBs. Measurements of junction temperature and component-PCB surface temperature distributions were used to identify the most appropriate modeling methodology for both the component and the PCB. Based on these results, a new PCB modeling methodology is proposed that conserves the need for modeling detail without compromising prediction accuracy