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By Dr.Zhang from Nanjing Normal University | 18 June 2019 | 0 Comments

See Limitless Opportunities in Aluminum Nitride.

See Limitless Opportunities in Aluminum Nitride.

What is aluminum nitride?
Aluminum nitride is an inorganic compound of aluminum and nitrogen, and its chemical formula is AlN. It is not a natural compound and must be synthesized artificially.
Aluminum nitride has the characteristics of high thermal conductivity, high resistivity and good corrosion resistance, which makes it an ideal material for thermal management and electrical applications. Besides, aluminum nitride is a common substitute for beryllium oxide (BeO) in the semiconductor industry because it does not pose a health hazard when processed. Aluminum nitride has thermal expansion coefficient and electrical insulation properties, which closely match the thermal expansion coefficient and electrical insulation properties of silicon wafer materials. Therefore, aluminum nitride is a useful material in electronic applications where high temperature and heat dissipation problems often occur.
Aluminum nitride is usually found on substrates 1mm thick and is easily cut by lasers. It can also be in thicker form, but if the parts require custom materials or significant machining, small batch production can be difficult or expensive. Shapal Hi-M Soft is often used as an alternative to pure aluminum nitride because it also provides high thermal conductivity and can be processed into complex geometric shapes.

What are the properties of Aluminum nitride?
  • Aluminum nitride is a covalently bonded material with hexagonal crystal structure, and it is homoplastic with a zinc polysulfide called wurtzite. The spatial group of this structure is P63mc.
  • This material is stable at high temperature of inert atmospheres. In air, surface oxidation occurred at more than 700℃, and surface oxidation layers of 5-10nm were detected even at room temperature. This oxide layer can protect the material up to 1370°C. Bulk oxidation occurs above this temperature. Aluminum nitride is stable in hydrogen and carbon dioxide environments below 980℃.
  • The material is dissolved slowly in inorganic acid by erosion of grain boundary and in strong alkali by erosion of aluminum nitride grain. The material hydrolyzes slowly in water. Aluminum nitride is resistant to most molten salts, including chlorides and cryolite.
  • Aluminum nitride is synthesized by carbon thermal reduction of alumina or direct nitridation of aluminum. The use of sintering aids and hot pressing requires the production of compact technical grade materials.

What are the applications of aluminum nitride?
  • Due to the piezoelectric properties of aluminum nitride, epitaxial aluminum nitride films are used for surface acoustic sensors deposited on silicon wafers. One such application is a radio frequency filter widely used in mobile phones, called a thin film body acoustic resonator (FBAR). This is an MEMS device that uses aluminum nitride sandwiched between two metal layers.
  • Aluminum nitride is also used to make piezoelectric micro-mechanical ultrasonic sensors that transmit and receive ultrasonic waves, and it can also be used for in-air rangefinding in a distance up to a meter.
  • The metallization methods allow AlN to be used in electronic applications similar to alumina and beryllium oxide. AlN nanotube is a kind of inorganic quasi-one-dimensional nanotubes with carbon nanotube and other electrons, which is considered as a chemical sensor of toxic gas.
  • In industry and academia, there are also many research efforts to apply aluminum nitride to piezoelectric MEMS applications. These include resonators, gyroscopes and microphones.

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