Radially varying air gap for near-ideal low cost passive heat spreaders

Abstract

This paper presents a method to optimize surface temperature of a mobile device by varying the thickness of an air gap as a function of distance from a heat source. It is demonstrated that this type of design offers a higher power budget when compared to a uniform air gap. The paper provides: ● A derivation of the equation used to calculate a radially varying air gap. It is based on the equation for radial fin efficiency which has been used extensively in electronics cooling but has not yet been applied to this problem. ● A description of how to manufacture a curved heat spreader used to maintain the varying air gap for both an ideal circular shape and a realistic phablet. ● A comparison of performance to a flat plate in both cases (ideal and phablet). In the case of a phablet with a partial heat spreader, the curved heat spreader can increase system power budget by 13% and the SoC power budget by as much as 25% when compared to a flat version. ● A discussion of the next steps