Vaporizable Dielectric Fluid Cooling of IGBT Power Semiconductors

Liquid cooling system concepts for power semiconductors and other applications have traditionally focused on the use of a single-phase liquid, typically water modified with anti-freeze agents (ethylene or propylene glycol), corrosion inhibitors, and other additives; or the use of single-phase deionized water. Selection of such a common liquid coolant is driven by commonality requirements, the traditional knowledge and experience with water and water systems, and the perception of simplicity. A wide vendor base exists for components and various additives. The typical solution is a single-phase pumped loop system with sensible heat transport, high flow rates, and relatively large volumes of water and large component sizes. Use of other fluids has been investigated and, especially in military and aerospace applications, a small number of other fluids have become common to meet specialized requirements. Recently, the use of a vaporizable dielectric fluid (VDF) in a pumped liquid cooling system has been demonstrated and commercialized as a practical system-level thermal management solution for isolated gate bipolar transistors (IGBTs) in electrical drives and for commercial processors for computing systems. The use of this type of fluid and a two-phase cooling system concept for cooling semiconductor and other devices impacts several aspects of system design, including liquid coolant heat capacity, need for additives, safety, potential for volume reduction, and electrical hazard prevention. Advantages of a two-phase system using newly-developed liquid pumps and isothermal liquid cold plates are described; positive and negative aspects for certain applications are described. This system concept also offers advantages for developing hybrid and electric vehicle powertrain components and batteries.