Aluminium Nitride (AIN)

• Material composition

High purity aluminum nitride (ALN) is used as the substrate, and the purity is usually greater than or equal to 90%. The common specifications are 92%,96% and 99%. The purity directly affects the thermal conductivity and electrical properties.

Burning agent: such as yttria (Y₂O₃), calcium oxide (CAO), magnesium oxide (MGO), etc., to reduce the sintering temperature (usually added <5%).

Firing additives: such as silica (SIO₂), optimize grain structure, inhibit grain boundary defects

• Manufacturing process

The manufacturing process of aluminum nitride ceramic substrate can be divided into the following key steps:

1. Raw material preparation: high purity ALN powder is mixed with sintering additives, dispersants and other materials, and ball-milled to sub-micron level to ensure uniform composition.
2. Forming process:

Dry pressing: the body is made by high pressure (50-200 MPA), suitable for simple shaped substrates.

Flow forming or injection molding: used to prepare substrates with complex shapes or multi-layer structures.

3. Sintering: High temperature sintering in an inert atmosphere (such as nitrogen) at 1600-2000℃ to form a dense ceramic structure, the temperature and time should be strictly controlled to avoid abnormal grain growth.
4. Post-processing:

Surface treatment: grinding and polishing to improve flatness (surface roughness can be as low as RA 0.03-0.05ΜM), grinding to high precision (flatness ≤5ΜM)

Metallization: circuit connections are achieved by sputtering (TI/CU/AU), thick film printing (AG-PD) or active metal brazing (AMB technology).

• Material properties

The core performance indexes of aluminum nitride ceramic substrate are as follows:

| function           | Values/characteristics                                                  | Advantageous scenarios

| heat conductivity         | 160-260 W/ (M · K) (96% purity)                                 | Efficient heat dissipation is 5-8 times that of alumina

| Thermal expansion coefficient | 4.0-6.0 x 10⁻⁶/℃                                               | Matched with silicon chips to reduce thermal stress

| Insulation strength | 15-20 KV/MM                                                 | High pressure environment stability

| Mechanical strength | Bending strength> 400 MPA fracture toughness 3~4 MPA·M¹/²                     | Resistant to mechanical shock and vibration

| High temperature resistance | Long term use temperature>2200℃ (inert atmosphere)                            | Applicability of high temperature environment 600℃

| Dielectric constant | 8.8 (1 MHZ)                                                 High frequency signal low loss

Chemical stability | resistant to acid, alkali and molten metal erosion                                       | Applicable to chemical and metallurgical fields

| Resistivity | Volume resistivity>10¹⁴ Ω·CM Dielectric constant about 8.5~9 (1MHZ), lower than alumina (9~10) | Suitable for chemical and metallurgical fields

Chemical stability | resistant to acid, alkali and molten metal erosion                                       | Applicable to chemical and metallurgical fields

Chemical stability | resistant to acid, alkali and molten metal erosion                                       | Suitable for chemical and metallurgical fields

• Industry applications

1. Power electronics and semiconductors:

High thermal conductivity (170-260 W/ (M·K)) supports the heat dissipation requirements of high power density devices (IGBT, MOSFET module, SIC module), and the operating temperature can reach more than 300℃.

2. LED lighting:

The thermal expansion coefficient matches the LED chip (such as GAN) to avoid thermal stress cracking; the thermal conductivity is 5-10 times that of alumina, extending the life to more than 50,000 hours.

3. Microwave and RF communications:

Low dielectric loss (TANΔ<0.0002), suitable for 5G millimeter wave band and high frequency radar system, microwave circuit substrate, RF filter

4. Aerospace and high temperature equipment:

High temperature resistant (2000℃ non-oxidizing environment), radiation resistant (>100 KGY Γ ray), lightweight design (density 3.26 G/CM³). Engine nozzle, satellite power dissipation components

5. Automotive electronics

Engine control module: aluminum nitride ceramic substrate for high power modules in automotive electronics.

6. Photoelectric devices

Laser diode: Aluminum nitride ceramic substrate is used for laser packaging to improve heat dissipation performance and stability.

• Comparison with other ceramic substrates

| Material | Thermal conductivity [W/ (M · K)] | Cost | Typical application scenarios               |

| Aluminum nitride | 170~200          | High power laser, 5G RF module |

| Aluminum oxide | 20~30            | Low | Medium low power LED, sensor |

| Silicon nitride | 70~100           | Medium | High temperature, high frequency devices             |

• high matching applications

Aluminum nitride ceramic substrate is irreplaceable in the following fields:

• High power electronics: such as new energy vehicles, photovoltaic inverters, power electronic modules.
• High frequency communication: 5G base station, millimeter wave radar, satellite communication.
• Extreme environment equipment: aerospace engines, nuclear reactor cooling systems.

Precision optics and sensors: infrared window, MEMS ultrasonic transducer.

• Future development trends

1. Develop high purity (> 99.9%) aluminum nitride ceramic substrate to improve performance and reliability.
2. Develop thinner aluminum nitride ceramic substrates to improve integration and heat dissipation performance.
3. New functions (anti-reflection, self-cleaning) are given to the substrate through surface modification or coating process.
4. Promote environmentally friendly aluminum nitride ceramic manufacturing process to reduce energy consumption and pollution

Aluminum nitride ceramic substrates, with their high thermal conductivity, low thermal expansion, heat resistance, and chemical stability, have become the core material for semiconductor packaging, high-power cooling, and high-frequency devices. Their application advantages in high-value-added fields (such as new energy vehicles and 5G communications) are significant, but they come at a higher cost (about 2 to 3 times that of alumina), making them more suitable for scenarios with stringent performance requirements. With the widespread adoption of third-generation semiconductors (such as GAN and SIC), the demand for aluminum nitride substrates will continue to grow.