Experimental characterization of board conduction sheets

A series of experiments assessing the impact of circuit board thermal conductivity on the thermal performance of air-cooled electronic component arrays is described. Simulated low-profile, surface-mount components in the form of small copper pieces with heat dissipating thick film resistors are employed. From one to five of these components are mounted in standardized square pitch arrays on three different circuit board samples: standard glass epoxy (k=0.26 W/m°K), three-layer (metal-glass epoxy-metal) board of moderate effective conductivity (k=1.14 W/m°K), and a three-layer high conductivity sample (k=35.9 W/M°K). These configurations were tested under forced and natural convection conditions. Profiles of board temperature were acquired using simultaneous thermocouple measurements. The data show that while convection accounts for approximately 80% of the component heat removal in forced air-cooling on the glass epoxy board, conduction to the board can carry nearly all (96%) of the heat load in natural convection cooling on a highly metalized board. The use of moderate conductivity boards increases the effective heat transfer area of a component by a factor of three or more