A non-dimensional correlation for the external thermal characteristics of surface mount metal quad flat packs

A non-dimensional correlation has been developed for the external thermal characteristics (case-to-air thermal resistance) of a surface mount metal quad flat pack in the mixed convection regime. This correlation uses Reynolds, Prandtl and modified Nusselt and Raleigh numbers, and is based on the model proposed by Churchill for correlating heat and mass transfer from simple surfaces, like flat plates. This modified Nusselt number can be interpreted as a non-dimensional external (case-to-air) thermal resistance. Cavity-down type 28 mm 208-leaded metal quad flat packs were tested to determine their thermal characteristics over a range of powers and air flow velocities. All the data up to 2 m/s air flow velocity was fitted to the proposed non-dimensional correlation with a maximum deviation of 5%. Such a non-dimensional correlation for the thermal characteristics of electronic packages provides a convenient basis for interpolating and extrapolating the test data. It also provides a simple way for using the laboratory test data at nominal temperatures and sea level conditions to estimate the thermal performance at higher temperatures and altitudes. This paper describes the tests that were done for characterizing the thermal performance of surface mount metal quad flat packs, and reviews the development of the non-dimensional correlation to represent the external thermal resistance