Microfluidic Cooling of a 14-nm 2.5-D FPGA With 3-D Printed Manifolds for High-Density Computing: Design Considerations, Fabrication, and Electrical Characterization

Abstract

The 2.5-D integration is becoming a common method of tightly integrating heterogeneous dice with dense interconnects for efficient, high-bandwidth inter-die communication. While this tight integration improves performance, it also increases the challenge of heat extraction by increasing aggregate package powers and introducing thermal crosstalk between the adjacent dice. In this article, a microfluidic heat sink is used to cool a 2.5-D Stratix 10 GX field-programmable gate array (FPGA) consisting of an FPGA die surrounded by four transceiver dice. The heat sink utilizes a heterogeneous micropin-fin array with micropin-fin densities that are tailored to the local heat fluxes of the underlying dice. Enabled through a 3-D printed enclosure for fluid delivery, the assembled heat sink has a total height of 6.5 mm, including the tubes used for fluid delivery. The heat sink is tested in an open-loop system with deionized water as a coolant, and thermal performance is compared against a high-end air-cooled heat sink. Improvements in die temperatures, computational density, and thermal coupling between the dice are observed. The effect of the FPGA power on the surrounding transceiver die temperatures was reduced by a factor of ${10}\times$ to over ${100}\times$ when compared with the air-cooled heat sink.