Aluminum Nitride: Outperforming Aluminum Oxide in Performance, Why Does Its Market Share Remain Below 30%?
In modern industry, ceramic materials play a crucial role due to their unique physical and chemical properties. Among aluminum-based ceramics, aluminum nitride (AlN) and aluminum oxide (Al₂O₃) are two types of materials that have attracted significant attention, yet their market positions are distinctly different: aluminum oxide dominates the mainstream market, while the penetration rate of aluminum nitride is less than 30%. Why has aluminum nitride, which boasts superior performance, failed to replace aluminum oxide? This article will delve into the scientific logic and industrial realities behind this phenomenon.
I. The "Outstanding" Advantages of Aluminum Nitride
1. Thermal Conductivity: The Physical Essence of Overwhelming Differences
The thermal conductivity of aluminum nitride (170-200 W/(m·K)) is 7 to 10 times that of aluminum oxide (20-30 W/(m·K)).
This gap stems from the difference in their crystal structures:
- Crystal Structure of AlN: Aluminum nitride (AlN) belongs to the hexagonal crystal system. In its structure, aluminum atoms and nitrogen atoms are connected by strong covalent bonds, forming a dense atomic arrangement. This structure not only has high bond energy but also exhibits low propagation resistance for lattice vibrations (phonons), allowing heat to be conducted efficiently.
Limitations of Al₂O₃: In the crystal structure of aluminum oxide (α-Al₂O₃, corundum structure), oxygen atoms occupy a relatively large space. The ionic bond characteristics between aluminum atoms and oxygen atoms lead to severe scattering of lattice vibrations, which hinders heat conduction.
This property makes aluminum nitride (AlN) the preferred thermal management substrate for high-power semiconductors, 5G base stations, and LED packaging. For instance, AlN substrates can reduce the chip junction temperature by more than 30%, significantly extending the service life of devices.
2. Insulation Performance: The "Guardian" for High-Temperature and Extreme Environments
The dielectric constant of aluminum nitride (AlN) is 8.8, which is lower than that of aluminum oxide (Al₂O₃) (9.8). Moreover, in high-temperature (>500°C) or high-humidity environments, AlN exhibits superior stability in insulation resistance. This advantage stems from the strong covalent nature of its chemical bonds and low oxygen vacancy defect density. In applications such as aerospace and electric vehicle battery modules, AlN can prevent safety hazards caused by partial discharge.
3. Chemical Stability: Dual Protection Against Corrosion and Radiation
Aluminum nitride (AlN) exhibits far stronger corrosion resistance to molten metals (such as aluminum and copper) than aluminum oxide (Al₂O₃). Furthermore, in high-radiation environments (e.g., the nuclear industry), its crystal structure is much less likely to be damaged. For instance, after the Fukushima Daiichi nuclear power plant accident in Japan, aluminum nitride was designated as a key research focus for radiation-resistant materials.
II. Penetration Rate Below 30%: The Dual Dilemmas of Aluminum Nitride in Technology and Market
1. Preparation Process: Crossing the "Valley of Death" Between Laboratory and Mass Production
The industrialization of aluminum nitride (AlN) begins with a battle against physical limits. Its synthesis process must be carried out in a high-temperature nitrogen environment at over 1800°C, and the purity of aluminum powder must exceed 99.99%. Any trace oxygen impurities (exceeding 0.1%) will trigger the formation of AlON (aluminum oxynitride) secondary phases—analogous to planting "thermal conduction landmines" in the pure crystal—causing the thermal conductivity to plummet by more than 30%.
What is more challenging is the sintering process: traditional pressureless sintering struggles to achieve densification. If hot isostatic pressing (HIP) technology is adopted, equipment costs will soar; if sintering aids such as Y₂O₃ are added, although the temperature can be reduced, secondary phase particles will form inside the material, hindering the smooth transmission of phonons.
In contrast, the preparation of aluminum oxide (Al₂O₃) is a symphony of industrial maturity. Its raw material costs are low, and its process window is wide—dense ceramics can be obtained through conventional sintering at temperatures below 1500°C, with production costs only 1/3 to 1/2 of those of aluminum nitride (AlN). This nearly "overwhelming" cost advantage keeps aluminum oxide far ahead in the industrialization race.
2. Supply Chain Disruptions: Monopolized Raw Materials and "Chokepoint" Processing
Aluminum nitride’s (AlN) dilemmas are not limited to technology, but also extend to every link in the industrial chain. On the raw material side, the production of high-purity aluminum nitride powder has long been monopolized by enterprises from Japan, the United States, and other countries. The price of imported powder is as high as 200-300 US dollars per kilogram, while domestic powder struggles to break through the technical barriers of purity and particle size distribution due to unstable mass production processes. By contrast, the price of aluminum oxide (Al₂O₃) powder is only 5-10 US dollars per kilogram—a difference in "weight class" comparable to that between a giant elephant and an ant.
Moving to the processing stage, the hard and brittle characteristics of aluminum nitride (AlN)（with a Mohs hardness of 8-9）present a new obstacle. Microcracks are prone to form during laser cutting, the drilling yield rate is less than 60%, and processing costs account for over 40% of the total cost. A person in charge of a domestic packaging enterprise once admitted: "For every 100 AlN substrates processed, 15 are scrapped due to edge chipping. This kind of loss is almost non-existent in aluminum oxide (Al₂O₃) production lines."
3. Dilemma on the Application Side: The Dual Shackles of Inertial Thinking and Standards
Even if the technology is feasible, the lag in market awareness continues to hinder the popularization of aluminum nitride (AlN). A "design inertia" is prevalent among engineers—specifically in the field of IGBT module packaging, switching to AlN substrates would mean the thermal management structure needs to be redesigned and validated, potentially extending the R&D cycle by 6 to 12 months. The chief technology officer (CTO) of a semiconductor enterprise revealed: "Customers would rather accept the temperature rise risk of aluminum oxide (Al₂O₃) substrates than adjust their production lines for a new material."
A deeper resistance stems from the lack of a standardized system. Aluminum nitride (AlN) has not yet had a unified industry testing specification, forcing enterprises to establish their own evaluation systems. Data from a third-party testing organization shows that for the same batch of AlN substrates, the difference in thermal conductivity test results among different manufacturers can reach 15%. This uncertainty further drives up the cost of market introduction.
In cost-sensitive fields such as consumer electronics, aluminum nitride’s (AlN) disadvantages become even more prominent. Take smartphone heat sinks as an example: the cost of an aluminum oxide (Al₂O₃) solution is only $0.3–$0.5 per piece, while even if AlN is reduced in price to $2 per piece, it still cannot escape doubts about "excessive performance." This gap in cost-effectiveness firmly confines AlN to high-end niche markets.
Conclusion: The Game Between Performance and Cost Is Far from Over
The competition between aluminum nitride (AlN) and aluminum oxide (Al₂O₃) is, in essence, a trade-off between material performance and industrialization capabilities. Although AlN holds a technical high ground, its widespread adoption still requires overcoming multiple hurdles in cost, manufacturing processes, and market awareness. With the accelerated pace of localization and the surge in emerging demand, the next decade may become a critical period for AlN to transition from a "laboratory star" to an "industrial mainstay."