What Is Aluminum Nitride?
Aluminum nitride (AlN) is an inorganic compound with colorless or gray crystals. It stands out for its high thermal conductivity and low electronic conductivity, making it exceptionally stable against oxidation among nitrides.
Uses of Aluminum Nitride
Aluminum nitride is primarily used in heat-sensitive semiconductor and electronic components due to its excellent thermal conductivity, electrical insulation, and similar thermal expansion properties to various semiconductors. It finds applications in substrates for power transistor modules, LED mounting, and IC packages, as well as plasma etch components, wafer chucks, and heater equalization plates. Additionally, its fine powder form improves resin performance by enhancing filler compatibility, flowability, and heat dissipation when mixed with resins like epoxy, silicone, and BT resin.
Properties of Aluminum Nitride
AlN is a colorless or gray crystalline solid with a molecular weight of 40.99 and a specific gravity of 3.3. It decomposes at 2,150°C without melting under ambient pressure. The sintered form is chemically stable and insoluble in common acids and bases. However, powdered AlN reacts with water vapor to form aluminum hydroxide and ammonia, particularly in high-pH solutions. Therefore, powdered AlN requires storage in high-purity nitrogen or dry air to prevent hydrolysis, unlike its sintered form, which exhibits high chemical resistance and does not decompose upon hydrolysis.
Sintered aluminum nitride, formed by mixing AlN powder with binders and sintering at temperatures above 1,700°C, offers high thermal conductivity (70 to 200 W/m-K) and thermal emissivity, significantly surpassing alumina (Al2O3) and matching the thermal expansion coefficient of silicon, enhancing its resistance to thermal deformation and shock.
Other Information on Aluminum Nitride
Aluminum Nitride Production Methods
Aluminum nitride can be synthesized through several methods:
1. From Aluminum Oxide: A high-pressure reaction between bauxite, coke, and nitrogen at 1,700°C yields AlN.
Al2O3 + 3C + N2 → 2AlN + 3CO
2. Direct Reaction of Aluminum Powder With Nitrogen: Aluminum powder reacts with nitrogen at 600°C, with the process optimized between 800 to 1,000°C to prevent agglomeration.
2Al + N2 → 2AlN
3. Reaction of Aluminum Chloride With Ammonia: This method, suitable for forming thin films, involves reacting aluminum chloride with ammonia at 1,200 to 1,500°C.
AlCl3 + NH3 → AlN + 3HCl