Immersion-cooled heat sinks for electronics: insight from high-speed photography

The development of effective heat sinks for the primary heat-dissipating component of a typical portable electronics device is an ongoing challenge. Thermal management using air-cooling is limited by the inherently limited thermal properties of the coolant. Other alternatives, including liquid immersion cooling, phase-change materials, and heat pipes, may merit consideration if the basic mechanisms can be reliably predicted. This study sheds light on the nucleation characteristics of an etched cavity-enhanced surface for use in an immersion-cooled heat sink. The target application is a high-density multichip module with several heat dissipating sources. High-speed photography was used to record parameters such as bubble interactions, bubble size, departure frequency and active site density while varying the cavity spacing and heat flux. The cavities, which have a characteristic dimension of approximately 40 /spl mu/m, are arranged in a square cluster 12.7 mm on each side. It was determined that the contribution of latent heat as a heat dissipation mechanism is only minor (less than 16%). In addition, it is proposed that the latent heat dissipation percentage may be used as a thermal performance indicator. Interactions between neighboring heat sources were also studied. These interactions decreased the bubble departure frequency and thereby affected the latent heat contribution.