In the rapid development of power electronics, high-frequency communication, and semiconductor technology today, the increasing power density and integration level of electronic components have made thermal management a core factor determining product performance, reliability, and lifespan. Traditional organic PCB substrates (like FR-4), with their low thermal conductivity (typically <0.5 W/m·K), struggle to meet the heat dissipation demands of high-power scenarios. In this context, high thermal conductivity ceramic substrates have emerged as an ideal solution for advanced electronic cooling, thanks to their exceptional overall properties.
Ceramic substrates are not a single material but a category of circuit substrates using inorganic non-metallic materials like alumina (Al₂O₃), aluminum nitride (AlN), and silicon nitride (Si₃N₄) as the insulating layer. Their advantages over traditional substrates are fundamental:
- Excellent Thermal Properties:
- Hög värmeledningsförmåga: Wide range (24 ~ 200+ W/m·K), enabling rapid heat transfer from chips to heat sinks, significantly lowering junction temperature, and improving device efficiency and lifespan.
- Low and Matched Coefficient of Thermal Expansion (CTE): The CTE of ceramics is very close to that of semiconductor chips (like Si, SiC, GaN), greatly reducing stress generated during thermal cycling, preventing chip cracking and solder joint fatigue.
- Superior Electrical and Mechanical Properties:
- High Insulation Strength: Withstands high voltage breakdown, ensuring safety in high-voltage applications.
- Hög mekanisk hållfasthet: High flexural strength, compressive strength ≥500 MPa, structurally stable.
- Good Chemical Stability: Resistant to corrosion and moisture, suitable for harsh environments.
- Advanced Circuitry Capabilities:
- Strong Copper Layer Bonding: Achieves firm bonding between the copper layer and ceramic (>20 N/mm) through special processes.
- High Circuitry Precision: Supports micron-level circuits (minimum line width/spacing can reach 0.05mm), meeting high-density integration requirements.
2. Comparison of Mainstream Ceramic Substrate Materials
Different ceramic materials have their own focus to meet diverse application needs. The following is a comparison of the three mainstream materials:
| Characteristic/Parameter | 96% Alumina (Al₂O₃) | Aluminiumnitrid (AlN) | Silicon Nitride (Si₃N₄) | Remarks/Application Tendency |
|---|
| Thermal Conductivity (W/m·K) | 24 – 30 | 170 – 220 | 80 – 90 | AlN is the preferred choice for ultra-high thermal conductivity; Si₃N₄ offers balanced performance. |
| CTE (×10⁻⁶/℃) | 6.5 – 8.0 | 4.5 – 5.5 | 2.5 – 3.5 | Si₃N₄ CTE matches Si chips best. |
| Mekanisk styrka | Hög | Relativt hög | Extremt hög (Excellent flexural strength) | Si₃N₄ offers the best thermal shock resistance, ideal for severe temperature cycling. |
| Kostnadsfaktor | Kostnadseffektivt | Högre | Hög | Al₂O₃ is the most widely used, mature, and economical option. |
| Typiska tillämpningar | General-purpose power modules, LED lighting | High-power IGBTs, Laser Diodes (LD), 5G RF power amplifiers | New energy vehicle motor drives, power modules for extreme environments | Selection based on heat dissipation needs, reliability requirements, och cost budget. |
3. Key Manufacturing Processes
The process is key to achieving the perfect bond between ceramic and metal. The three mainstream processes determine the final performance ceiling of the substrate.
- DBC (Direct Bonded Copper) Process
- Process: Copper foil and ceramic surface undergo eutectic melting at high temperature (1065~1085°C) in an oxygen-containing nitrogen atmosphere, forming strong Cu-O chemical bonds.
- Egenskaper:
- Fördelar: Thick copper layer (typically 100μm~600μm), high current-carrying capacity, excellent thermal conductivity.
- Challenges: Requires strict control of temperature and atmosphere; relatively lower circuit precision (line width/spacing typically >100μm).
- Tillämpningar: High-current, high-heat-dissipation power modules (e.g., electric vehicle inverters).
- DPC (Direct Plated Copper) Process
- Process: Utilizes semiconductor processes: first, sputtering a metal seed layer onto the ceramic substrate, then forming circuits through photolithography, electroplating, and etching.
- Egenskaper:
- Fördelar: Very high circuit precision (can reach micron-level), high surface flatness, suitable for complex and fine wiring.
- Challenges: Plated copper layer is relatively thin (typically 10μm~100μm), slightly weaker for very high currents, and higher cost.
- Tillämpningar: Fields requiring high precision, such as laser packaging, RF/microwave, sensors.
- AMB (Active Metal Brazing) Process
- Process: An optimization based on DBC, using brazing paste containing active elements (e.g., Ti, Zr) to bond copper and ceramic in a vacuum or inert atmosphere.
- Egenskaper:
- Fördelar: Bond strength far exceeds DBC, higher reliability, especially suitable for aluminum nitride (AlN) substrates. Excellent resistance to thermal fatigue.
- Challenges: Most complex process, highest cost.
- Tillämpningar: Fields requiring ultra-high reliability, such as aerospace, high-speed rail, and new energy vehicle main drive inverters (especially for SiC power modules).
4. Technical Parameter Selection Reference
Using Jingci Precision Tech as an example
| Föremål | Standard Capability | Customizable Range | Explanation |
|---|
| Substratmaterial | 96% Alumina, Aluminum Nitride | Silicon Nitride, Zirconia, Silicon Carbide, etc. | Choose based on thermal, strength, and cost needs. |
| Brädans tjocklek | 1,0 mm | 0.25mm ~ 3.0mm | Thin boards aid lightweighting; thick boards enhance mechanical strength. |
| Outer Layer Cu Thickness | 100μm (approx. 3oz) | 5μm ~ 400μm | DBC/AMB typically ≥100μm; DPC can be thinner. |
| Min. Linjebredd/avstånd | 0.05mm (DPC Process) | Depends on the process | DPC process achieves the highest precision. |
| Ytfinish | ENIG (Electroless Nickel Immersion Gold) | Immersion Silver, Immersion Tin, ENEPIG, etc. | ENIG provides excellent solderability and oxidation resistance. |
| Via/Hole Process | – | Metallized Vias, Plated & Filled Vias, Edge Plating | Enables 3D interconnection and special structural designs. |
5. Broad Application Fields
High thermal conductivity ceramic substrates are the foundation of many high-tech industries:
- Semiconductors & IC Packaging: Provides a stable, low-temperature operating environment for CPUs, GPUs, FPGAs, and memory chips.
- Power Electronics & SiC/GaN Devices: Used in inverters, converters, UPS; the ideal “carrier” for wide-bandgap semiconductors like SiC/GaN.
- Elektronik för fordonsindustrin: Core heat dissipation component in ECUs, motor controllers, OBCs, LiDAR.
- 5G-kommunikation: Base station RF power amplifiers and antenna modules require ceramic substrates for efficient cooling to maintain signal stability.
- Lasers & Optoelectronics: Packaging for high-power LEDs, laser diodes (LD), photodetectors.
- Flyg- och rymdindustrin samt försvar: Electronic systems demanding utmost reliability and resistance to extreme environments.
6.Framtida utvecklingstrender
- Materialinnovation: Developing new materials with higher thermal conductivity (e.g., diamond composite ceramics) and better CTE matching.
- Process Fusion & Refinement: Combining the advantages of different processes (e.g., DPC+AMB) to further improve circuit precision and reliability.
- Integration & Modularization: Moving towards embedded components, 3D packaging (3D-IPAC) to reduce system size and enhance performance.
- Kostnadsoptimering: Reducing the cost of high-performance ceramic substrates through mass production and process improvements, broadening their market application.
Slutsats
High-thermal-conductivity ceramic substrates have become indispensable thermal management components in high-power, high-frequency applications. Correctly understanding their material properties and process variations, and selecting the appropriate type, is a critical step for engineers to design high-performance, highly reliable products.