Thermal Management of Electronics in Telecommunications Products: Designing for the Network Equipment Building System (NEBS) Standards

Abstract

The effects of altitude, increased ambient temperature, and increased relative humidity on the board level forced convection typical of telecommunications products were systematically examined through numerical simulation and analytical techniques. Altitude was found to have the most significant impact on component temperature rise above inlet air temperature. Depending on the proportion of upstream-heating to self-heating for a given component, the component temperature rise above inlet air temperature was found to increase by 40% to 88% at 5000m when compared to the base line case at sea level. Inlet air temperature was found to translate linearly to component temperature increase. The second-order effects due to property changes with temperature were found to be less than 3% on the component temperature rise. The relative humidity was not found to significantly impact the component temperature rise at an inlet temperature of 25°C. However, the property changes at a 55°C inlet were more significant, and require further study. A temperature multiplier concept is introduced to aid practicing engineers in extrapolating data at standard conditions to the operating extremes.