EPA's PFAS regulations will have a significant impact on liquid cooling

  At present, the industry generally believes that two-phase immersion and two-phase cold plate liquid cooling solutions are the hope for addressing the challenges of higher power CPU and GPU thermal management. However, in August 2022, the EPA designated PFAS as a so-called "forever chemicals" hazardous substance, which could have a significant impact on the IT industry's utilization of these two cooling technologies.

     Perfluorinated and perfluoroalkyl substances (commonly referred to as PFAS) are a type of synthetic chemicals that typically consist of a carbon backbone and fluorine saturated with most of the carbon, as well as at least one functional group (such as carboxylic acid, sulfonic acid, amine, or others), possessing unique and useful chemical and physical properties. These compounds have been widely used in consumer and industrial products since the 1950s, such as non stick pans, waterproof sports equipment, anti fouling carpets, cosmetics, and countless other commodities, as well as two-phase cooling in semiconductor manufacturing and IT industries.

  So far, most of the two-phase immersion cooling in data centers uses PFAS dielectric liquids Novec and Fluorinert produced by 3M. Initially, 3M attempted to find a solution to reduce the use of PFAS, but announced at the end of last year that it would completely stop production of PFAS by the end of 2025. This poses a direct risk of elimination for technologies that use these or similar PFAS liquids.

    Single phase immersion cooling and single phase cold plate cooling are competitive and alternative solutions for two-phase immersion cooling suitable for data centers. Single phase immersion cooling uses hydrocarbon based dielectric liquids, such as mineral oil and synthetic oil. In contrast to two-phase cooling based on fluorocarbon compounds, the single-phase coolant does not boil and therefore does not undergo phase transition during the cooling process. Due to the fact that dielectric coolants are better thermal conductors than air, this single-phase liquid cooling is very suitable for high-density racks and has a cost advantage over two-phase immersion cooling.

   In addition, the single-phase cold plate in the data center is a component that transfers heat from computer equipment. It consists of a metal plate with built-in pipes, which are connected to the top of the server's CPU, GPU, or other components and connected to the liquid circulation cooling system through pipes. The cold plate absorbs the heat generated by electronic equipment and transfers it to the liquid coolant, which then circulates from the equipment to the cooling unit for heat dissipation. Cold plate liquid cooling is based on a water-based coolant, completely eliminating the application concerns of PFAS type dielectric liquids.

   With the limited application and gradual phasing out of PFAS chemicals, it is urgent and important to develop and validate the next generation of immersed coolants for data centers.