Aluminum nitride (AlN) is a synthetic ceramic material with a hexagonal wurtzite structure, formed by the covalent bonding of nitrogen (N) and aluminum (Al) elements. Its combination of excellent physical and chemical properties makes it a critical material in numerous high-tech fields. Key Properties 1. Extremely High Thermal Conductivity: This is AlN's most prominent advantage. Its theoretical thermal conductivity is as high as 320 W/(m·K) (almost twice that of metallic aluminum), far exceeding that of commonly used alumina ceramics (approximately 20-30 W/(m·K)). Even at high temperatures (200-300°C), its thermal conductivity remains high (>200 W/(m·K)), which is crucial for heat dissipation in high-temperature applications. Its excellent thermal conductivity is the core reason for its widespread use in electronic packaging and heat dissipation applications. 2. Good Electrical Insulation: It has a high resistivity (>10¹⁴ Ω·cm), making it an excellent insulator. Its dielectric constant is relatively low (approximately 8-9 @ 1MHz), and its dielectric loss is small (<0.001 @ 1MHz), making it very suitable for high-frequency, high-speed electronic applications. 3. Thermal Expansion Coefficient Matching Silicon: Its coefficient of thermal expansion (CTE) is approximately 4.5-5.0 × 10⁻⁶ /K (room temperature to 300°C), very close to that of single-crystal silicon (approximately 3.5-4.0 × 10⁻⁶ /K) and gallium arsenide (GaAs, approximately 5.8 × 10⁻⁶ /K). This matching is extremely important in semiconductor packaging, significantly reducing thermal stress between the chip and the substrate/package, improving device reliability and lifespan. 4. High Mechanical Strength and Hardness: It possesses high flexural strength and Vickers hardness, with superior mechanical properties to alumina. 5. Excellent Chemical Stability and Corrosion Resistance: It is very stable at room temperature and resists corrosion from most acids, alkalis, and molten metals (such as aluminum and gallium). In air, at high temperatures (>700°C), the surface slowly oxidizes to form a protective alumina layer. 6. Wide Bandgap Semiconductor Properties (Intrinsic): With a bandgap width of up to ~6.2 eV, it is an ultra-wide bandgap semiconductor material. This gives it a high critical breakdown electric field, low leakage current, and potential for high-temperature, high-frequency, and high-power electronic device applications (however, doping to achieve n-type and p-type conductivity remains challenging, which is a bottleneck for its application as a semiconductor). 7. Good Optical Properties: It has high transmittance (theoretical value >80%) in the ultraviolet to infrared band (approximately 0.2-6 μm), and can be used for optical windows and sensors. It is also an excellent acousto-optic material. Applications of Aluminum Nitride Based on the above excellent properties, aluminum nitride is mainly used in fields requiring efficient heat dissipation, electrical insulation, thermal matching, and reliability: 1. Electronic Packaging and Substrates: High-power LED packaging substrates: This is currently the largest-scale application. AlN substrates can effectively dissipate the large amount of heat generated by LED chips, significantly improving luminous efficiency, brightness, and device lifespan. High-power semiconductor modules (IGBT, SiC, GaN) substrates: Used in power electronics, electric vehicles, rail transit, industrial inverters, etc. AlN copper-clad laminates (DBC or AMB) can withstand high power density and high temperatures, providing excellent insulation and heat dissipation capabilities. Microwave radio frequency (RF) packaging and substrates: Low dielectric constant and loss make it very suitable for high-frequency circuits (such as base stations, radar, and satellite communications). Multi-chip modules (MCM) and hybrid integrated circuit (HIC) substrates: Provide the heat dissipation and electrical insulation required for high-density interconnections. Laser diode (LD) heat sinks: Efficient heat dissipation is crucial for LD performance and lifespan. 2. Heat Dissipation Components: Heat sinks and heat covers for high-heat-generating electronic components such as CPUs and GPUs. Substrates for thermoelectric coolers (TEC). Heat dissipation structural components requiring high thermal conductivity and insulation. 3. Piezoelectric and Surface Acoustic Wave Devices: It exhibits a piezoelectric effect and can be used to manufacture high-temperature, high-frequency surface acoustic wave (SAW) filters, bulk acoustic wave (BAW) resonators, and other devices. 4. Wide Bandgap Semiconductor Materials: As an ultra-wide bandgap semiconductor, it has potential applications in deep ultraviolet optoelectronic devices (such as UVC LEDs and detectors), high-temperature/high-frequency/high-power electronic devices (such as HEMTs), and radiation detectors, and is a research hotspot. 5. Refractory Materials and Crucibles: Utilizing its high melting point, chemical inertness, and resistance to molten metal corrosion, it is used as crucible and furnace lining materials for melting high-purity metals (such as aluminum, gallium, and arsenic) and semiconductor single crystals (such as gallium arsenide). 6. Optical Applications: Ultraviolet/infrared optical windows (requires high purity and transparency). Acousto-optic modulators. 7. Wear-Resistant and Corrosion-Resistant Components: Wear-resistant components, nozzles, and seals in special environments (such as corrosive media and high temperatures).

Silicon nitride (Si₃N₄) is a high-performance ceramic material. Due to its excellent mechanical strength, thermal shock resistance, electrical insulation, and moderate thermal conductivity, it has attracted significant attention as a substrate material in electronic packaging, power modules, and high-temperature devices. Core Advantages High Mechanical Strength: Bending strength is 2-3 times that of Al₂O₃, excellent thermal shock resistance, suitable for high-power modules. Good Thermal Matching: CTE is close to Si and SiC chips, reducing failures caused by thermal stress. Comprehensive Thermal Management Capabilities: Although the thermal conductivity is lower than AlN, the mechanical properties are superior, suitable for high-reliability scenarios. 2. Applications of Silicon Nitride Substrates (1) Power Electronics Packaging -IGBT Modules: Replacing Al₂O₃/AlN to improve thermal shock resistance (e.g., Toyota hybrid vehicles). -SiC/GaN Devices: Matching CTE to reduce the risk of chip cracking. (2) High-Frequency Communication -5G Radio Frequency Devices: Low dielectric loss (tanδ <0.001), suitable for millimeter-wave applications. Microwave Packaging: Used in radar and satellite communication systems. (3) High-Temperature Sensors Engine combustion chamber pressure sensors (high-temperature resistance, corrosion resistance). (4) LED Heat Sink Substrates High-power LED packaging, combining heat dissipation and mechanical support.