Heat-Transfer Microstructures for Integrated Circuits

摘要

Convective heat-transfer theory indicates that well over 1000 W/cm exp 2 can be compactly removed from ICs at normal operating temperatures, provided microscopic (e.g., 50- mu m wide) extended-surface structures are used. The difficulty of constructing high-conductance, low-stress thermal interfaces between ICs and heat sinks suggests the use of an integral heat sink. Accordingly, IC microfabrication techniques were employed to design, fabricate, and test novel, ultracompact water-cooled, laminar-flow, optimized plate-fin and pin-fin heat sinks directly within standard-thickness silicon substrates. Worst-case thermal resistances as low as 0.083 exp 0 C/W were measured from 1-cm exp 2 thin-film resistors. The use of integral liquid-cooled heat sinks in multichip systems presents potential yield, reliability, cost and packaging problems. Attachment of unmodified ICs to micro-heat sinks seems a more attractive approach. A novel die-attachment technique has been developed which avoids the problems of conventional attachments. In this technique, a liquid partially fills an array of micron-wide reentrant capillaries in the heat sink substrate, so that surface tension holds the polished back of an IC in intimate thermal contact with the heat sink. The bond is void-free, virtually stress-free, long-lived, and allows repeated detachment and replacement of ICs without damaging the heat sink substrate. The reentrant grooves were fabricated by a noval process using electroless plating of nickel onto vertical silicon microgrooves. For a 1-cm exp 2 area, typical interfacial thermal resistances of 0.022 exp 0 C/W at 300 W have been measured. In summary, microfabrication techniques have been employed to fabricate new, very high-performance liquid-cooled heat sinks having negligible volume (0.1 cm exp 3 ), and also to make a novel, stress-free, reusable microcapillary thermal interface between such heat sinks and integrated circuit substrates. (ERA citation 09:018933)