Evaluating the Reliability of Passive Server Components for Single-Phase Immersion Cooling

Abstract

The adoption of single-phase liquid immersion cooling (Sp-LIC) for Information Technology equipment provides an excellent cooling platform coupled with significant energy savings. There are, however, very limited studies related to the reliability of such cooling technology. The accelerated thermal cycling (ATC) test given ATC JEDEC is relevant just for air cooling but there is no such standard for immersion cooling. The ASTM benchmark D3455 with some appropriate adjustments was adopted to test the material compatibility because of the air and dielectric fluid differences in the heat capacitance property and corresponding ramp rate during thermal cycling. For this study, accelerated thermal degradation of the printed circuit board (PCB), passive components, and fiber optic cables submerged in air, white mineral oil, and synthetic fluid at a hoisted temperature of 45 °C and 35% humidity is undertaken. This paper serves multiple purposes including designing experiments, testing and evaluating material compatibility of PCB, passive components, and optical fibers in different hydrocarbon oils for single-phase immersion cooling. Samples of different materials were immersed in different hydrocarbon oils and air and kept in an environmental chamber at 45 °C for a total of 288 h. Samples were then evaluated for their mechanical and electrical properties using dynamic mechanical analyzer (DMA) and a multimeter, respectively. The cross section of some samples was also investigated for their structural integrity using scanning electron microscope (SEM). The literature gathered on the subject and quantifiable data gathered by the authors provide the primary basis for this research document.