Silicon Nitride

• Material composition

Silicon nitride ceramic substrate is mainly composed of silicon nitride (SI₃N₄), the content is usually 95%-99.9%, high purity (>99%) silicon nitride for high performance applications;

Sintering aids: such as aluminum oxide (AL₂O₃, 5%~15%), yttrium oxide (Y₂O₃, 3%~8%), and MGO) form liquid phases to promote particle reorganization, optimizing sintering performance and material density. Α-Si₃N₄ transforms into Β-Si₃N₄ at high temperatures, enhancing mechanical properties and reducing the sintering temperature to 1700~1900℃. Its chemical structure is based on covalent bonds, which exhibit high bond energy characteristics, endowing the material with excellent thermal stability and mechanical strength.

• Manufacturing process

1. Powder preparation

Carbon thermal reduction method:

Raw materials: quartz sand (SIO₂) mixed with carbon powder, nitrogen gas is introduced to react at 1400~1600℃:

3SIO₂ + 6C + 2N₂ → SI₃N₄ + 6CO↑

The product was acid washed and ball milled to obtain fine powder (particle size 1~5ΜM).

Chemical vapor deposition (CVD):

Reaction: 3SICL₄ + 4NH₃ → SI₃N₄ + 12HCL

Used for preparation of nanoscale powders or coatings.

2. Formation

Dry pressing: simple shape substrate, pressure 50~200 MPA.

Isostatic forming: complex structure (three-dimensional heat dissipation fin), pressure 100~300 MPA, high uniformity of body density.

Flow forming or injection molding: used for complex shapes or multi-layer structures, the addition of binder is required to improve fluidity

3. Sintering

Reaction sintering method: the silicon powder body is heated in stages (1250-1450℃) in nitrogen, and SI₃N₄ is generated through solid phase reaction. The process cycle is long but suitable for complex shapes.

Hot pressing sintering method: rapid densification at high temperature (1600-1850℃) and high pressure (25-50 MPA) to obtain high density (3.12-3.2 G/CM³) and high performance substrate, the density can reach more than 99% of the theoretical value.

Reaction sintering: silicon powder is preformed and nitrided for sintering, suitable for large size parts (such as crucible).

4. Post-processing

Precision machining: grinding and polishing to control surface roughness (RA <0.01 ΜM), diamond grinding wheel grinding, flatness ≤5ΜM.

Surface metallization: Sputtering TI/CU/AU layer or DBC (direct bonded copper) technology to achieve high reliability circuit connection

• Material properties

Performance indicators | Values/characteristics                     | Advantage scenarios

| heat conductivity         | 80-150 W/(M·K)                 | Efficient heat dissipation, better than alumina (20-30 W/ (M·K))

| Bending strength | ≥ 800 MPA                        High mechanical stability and strong impact resistance

| Fracture toughness | 6-8 MPA·M¹/²                   | Excellent crack resistance, twice that of alumina

| Thermal expansion coefficient | 2.5-3.5 x 10⁻⁶/℃                 | Matched with silicon chips (3-4 x 10⁻⁶/℃) to reduce thermal stress

| Heat resistance | Long-term temperature resistance>1200℃ (oxidation environment) | Suitable for extreme high temperature environment

| Insulation strength | 15-20 KV/MM                     High safety of high voltage electrical equipment

Corrosion resistance | Resistance to molten metal (aluminum, copper) erosion | Protection of metallurgical and chemical equipment

| Thermal shock resistance | can withstand rapid temperature changes (1000℃ cycle) | high temperature rapid change environment

| high-melting-point          |1900℃                         | Long-term working temperature ≤ 1400℃

| Electrostatic discharge resistance | Breakdown strength> 20 KV/MM              | Suitable for high voltage insulation

• Industry application technical index advantages

1. Power electronics and semiconductors:

High thermal conductivity and low thermal expansion coefficient, suitable for high power density devices (such as SIC, GAN modules), heat dissipation efficiency increased by more than 30%.

2. Aerospace:

High temperature resistance (> 1000℃) and lightweight (density 3.2 G/CM³) are used for engine thermal protection components and satellite power systems.

Lightweight: density 3.2 G/CM³, lighter than alumina (3.9 G/CM³), suitable for aerospace weight reduction requirements.

3. Mechanical manufacturing:

High hardness and wear resistance, used in ceramic bearings, turbine blades, life extended by more than 3 times.

4. Chemicals and energy:

Corrosion resistance and resistance to molten metal are used in electrolytic cell lining and polysilicon production equipment to improve process efficiency.

5. Biomedicine:

High biocompatibility for use in artificial joints and dental implants to reduce rejection.

• Industries that are particularly suitable

1. New energy vehicles: electronic control system, charging pile heat dissipation substrate (accounting for 75.8% of global demand).
2. High frequency communication: 5G base station RF devices, millimeter wave radar, suitable for high frequency and low loss requirements.
3. Aerospace: engine nozzles, thermal protection systems, tolerance to extreme temperatures and radiation.
4. High-end equipment manufacturing: precision bearings, cutting tools, improve the durability of equipment.
5. New energy and photovoltaic: Polysilicon reaction vessel, solar cell module, optimize production efficiency and reliability.Compare other ceramic substrates| Material | Thermal conductivity [W/ (M·K)] | Fracture toughness (MPA·M¹/²) | Typical application scenarios| Silicon nitride ceramic |80-150 W/ (M·K) | 6-8                   High power heat dissipation, extreme environment| Alumina ceramics | 20-30             | 3-4                   | General insulation, medium power scenarios

   | Aluminum nitride ceramics | 160-260           | 2-3                   | High thermal conductivity requirements (e.g., lasers)

   | Silicon carbide ceramics | 120-200           | 4-5                   | Ultra-high temperature structural parts

   Silicon nitride ceramic substrates, with their core advantages of high thermal conductivity, low thermal expansion, and high strength, are irreplaceable in high-power electronics and semiconductor manufacturing. Their unique chemical stability and lightweight characteristics make them key materials for extreme environments such as aerospace and automotive industries. In the future, with breakthroughs in nanocomposite technology (SI₃N₄-SIC) and additive manufacturing (3D printing), the demand for silicon nitride substrates will continue to grow. It is estimated that the market size will reach $770 million by 2030 (with an annual compound growth rate of 25.2%).