Corrosion of aluminum nitride under prolonged pool-boiling in water and corrosion mitigation by oxidation

Abstract Aluminum nitride (AlN) is a common electronics substrate known for its high thermal conductivity and durability, making it an attractive choice for integrated two-phase cooling approaches. However, AlN corrodes severely in contact with water. Here we evaluate the corrosion of AlN under boiling conditions in water for durations up to 150 h. Dense AlN substrates are directly heated with fluxes up to 100 W/cm 2 in water pools to produce vigorous boiling on their surface or exposed to ambient boiling environments. Corrosion depth is determined by profilometry following etching of corrosion products. Directly heated AlN substrates corrode dramatically faster (up to 225 nm/h) compared to a boiling ambient (25 nm/h). Corrosion rate is not found to depend on heat flux over a range of 60–80 W/cm 2 . These observations are consistent with reaction-limited kinetics based on literature studies of AlN powder corrosion kinetics. Surface oxide layers as thin as 1 µm, produced by thermal oxidation, protect AlN from corrosion in water for long-duration, high-heat flux pool boiling conditions. Aluminum coatings of 200 nm show no protection. The results further clarify the constraints and potential for AlN in high heat flux, phase change heat transfer applications with aqueous working fluids.