What is Aluminum Nitride?
Aluminum nitride (AlN) is a synthetic non-oxide advanced ceramic material that combines ultra-high thermal conductivity and a similar thermal expansion coefficient to Si and GaAs, reliable electrical properties, and excellent chemical stability. This makes it ideal for efficient thermal management and high-performance electronic components.
The Formula and Synthesis Methods
The chemical formula for aluminum nitride is aluminum and nitride. In modern industry, the three main synthesis methods are direct nitridation, carbothermal reduction, and chemical vapor deposition：
● Direct nitridation method: In a high-temperature nitrogen or ammonia atmosphere of 800~1200 ℃, aluminum powder directly reacts with nitrogen or ammonia to synthesize aluminum nitride powder. The chemical reaction formula is: 2Al(s)+N2(g)→2AlN(s)
● Carbon thermal reduction method: Heat the uniformly mixed Al2O3 and C at above 1500 ℃ in the N2 atmosphere; first, reduce Al2O3, then react the resulting product Al with N2 to generate AlN. The chemical reaction formula is: Al2O3 (s) + 3C (s) + N2 (g) ⇌ 2AlN (s) + 3CO (g)
● Chemical vapor deposition: A vapor phase growth technique synthesizes aluminum nitride on a substrate surface by controlling the flow and concentration of gaseous reactants.
The above three synthesis methods each have advantages and disadvantages. In practical applications, corresponding choices must be made based on the product's performance requirements and costs.
The Benefits of Aluminum Nitride
● High thermal conductivity
● Low thermal expansion rate
● Excellent dielectric properties
● High mechanical strength
● Excellent chemical stability
● Good metallization capacity
● No toxic issues than beryllia
● Excellent optical transmission characteristics
Ceramic Material Properties Comparison
| Item | Unit | Aluminum nitride(AlN) | Alumina (Al2O3) |
Beryllium Oxide (BeO)
|
Silicon Carbide(SiC)
|
| Thermal Conductivity (25℃) | W/mk | 170 | 30 | 300 | 170 |
| Thermal Expansivity (25~400℃) | 1 × 10 -6 /℃ | 4.5 | 7.3 | 8 | 3.7 |
| Maximum Working Temperature (Inert) | ℃ | 2200 | 1800 | 2000 | 1800 |
| Dielectric Constant | 1MHz | 8.8 | 8.5 | 6.5 | 40 |
| Dielectric Loss | 1MHz | 5*10 -4 | 3*10 -4 | 5*10 -4 | 500*10 -4 |
| Dielectric Strength (DC@25℃) | KV/mm | 15 | 10 | 10 | 0.07 |
| Flexural Strength (25℃) | MPA | 450 | 338 | 200 | 450 |
| Toxicity | No | No | Yes | Slight | |
| Cost | Middle | Low | High | High |
Notes:
● All parameters are under the state with no load.
● All parameters are typical ones based on a purity of 99%; they exhibit slight differences with different formulas and grades.
Post-processing of AlN Components
Post-processing is essential in practical applications to achieve precise fitting between AlN ceramic components and other parts, thereby improving surface quality. At present, the main types of post-processing are as follows:
1. CNC Milling and Grinding
Using ultra-high hardness abrasive grains in diamond grinding wheels, materials are ground and removed from the ceramic surface, primarily through grinding wheel grinding, diamond grinding, and drill grinding.
2. Laser Cutting
This method utilizes the high-energy laser beam generated by the laser to process aluminum nitride ceramics. It is suitable for precise cutting and drilling of products such as ceramic substrates.
3. Plasma-assisted Polishing
Utilizing the combined effects of plasma's physical bombardment and chemical reaction to achieve material removal to obtain a smooth, polished surface.
4. Chemical Mechanical Polishing (CMP)
A composite polishing process that uses both chemical etching and mechanical removal, widely used in the semiconductor industry.
5. Magnetorheological Finishing (MRF)
This method is between polishing and non-polishing. It is an ultra-precision machining method that utilizes the rheological properties of magnetorheological polishing fluid in a magnetic field to achieve polishing.
Our facility specializes in CNC grinding and laser processing technology on Aln ceramic and can provide customers with various customized, ultra-high-precision aluminum nitride parts with dimensional tight tolerances of ±0.005mm.
Typical Applications of Aluminum Nitride
● As high-power electrical insulators, especially where high electrical insulation and stable electrical performance are essential
● As a ceramic substrate for high-power electronics, chip carriers, and semiconductor packaging
● As a heat sink and heat spreader for high-power and radio frequency electronic devices
● As dielectric layers in optical storage media
● As an Ideal crucible and casting mold material for Al, Cu, Ag, and Pb metallurgy manufacturing
Due to aluminum nitride ceramic’s excellent thermal, physical, chemical, electrical, and optical properties, it is widely used in various high-power electronics, high-power lighting, new energy, semiconductor, military, aerospace, and other fields.
Conclusion
As a new technical ceramic material, aluminum nitride has played a significant role in many industries and fields. With the progress and breakthroughs in aluminum nitride powder production and preparation technology, as well as the continuous innovation of aluminum nitride ceramic components technology, it will be further expanded as a more optimized heat dissipation and electrical insulation component solution in the fields of microelectronics, optical devices, IGBT, emission control, rail transportation, aviation systems, and other fields.