Advantages of Applying AMB Substrates to SiC Power Devices

Silicon Carbide (SiC) holds significant advantages in high-frequency, high-voltage, and high-temperature operational environments due to its excellent thermal dissipation, compact size, low energy consumption, and high power capabilities. These attributes make SiC particularly advantageous in new energy vehicles, leveraging its inherent high-voltage and long-range capabilities. The integration of SiC into the automotive sector is currently a focal point in the new energy vehicle industry.

Choosing AMB Ceramic Substrates for SiC Power Devices

Ceramic substrates are categorized primarily into DBC (Direct Bond Copper), AMB (Active Metal Brazing), DPC, HTCC, LTCC, differentiated by their manufacturing processes and materials such as aluminum oxide (Al2O3), aluminum nitride (AlN), and silicon nitride (Si3N4). While aluminum oxide (Al2O3) is the most commonly used ceramic substrate with DBC technology, aluminum nitride (AlN) exhibits higher thermal conductivity, suitable for both DBC and AMB processes. Silicon nitride (Si3N4), known for its excellent reliability, is predominantly processed using the AMB technique.

Challenges with Traditional DBC Ceramic Substrates

Direct Bond Copper (DBC) ceramic substrates are produced using eutectic bonding, where copper and ceramics (Al2O3 or AlN) expand differently under high temperatures. This mismatch often leads to significant thermal stress, causing delamination of the copper layer from the ceramic surface. As a result, traditional DBC ceramic substrates struggle to meet the high-temperature, high-power, high-reliability packaging requirements.

The Role of Active Metal Brazing (AMB) Substrates

AMB substrates involve applying active brazing materials through thick-film printing or as solder sheets on the surface of ceramic carriers. Copper foils are then placed on both sides of the ceramic carrier coated with metal brazing materials, forming a structure of copper-brazing material-ceramic-brazing material-copper. Through stacking and vacuum sintering processes, ceramics, brazing materials, and copper foils are tightly bonded. Subsequent steps include exposure, development, etching, and surface treatments to produce the final product.

Benefits of AMB Substrates

AMB substrates achieve higher bond strength at the copper/ceramic interface. Si3N4 ceramics, known for their excellent mechanical properties and thermal conductivity compared to Al2O3 and AlN, ensure greater reliability during high-temperature operation. Hence, Si3N4-AMB coated copper ceramic substrates emerge as the preferred choice for SiC device encapsulation.

Future Prospects in Electric Vehicles

As the core supporting material for SiC power modules, AMB ceramic substrates are poised to facilitate breakthroughs in the electric vehicle sector. Beyond automotive applications, high-performance AMB substrates also find utility in photovoltaics, rail transportation, IGBT modules, SiC power devices, and silicon carbide ultra-high voltage electronic control and drive platforms.

Key Challenges in AMB Substrate Manufacturing: Brazing

Brazing is the critical process in AMB ceramic substrate manufacturing, focusing on the preparation of active brazing materials and achieving robust metal-ceramic bonds. Commonly used active metals include Ti, Zr, Hf, V, Nb, which effectively wet the ceramic surface and facilitate active bonding between ceramics and metals.

Conclusion

In conclusion, AMB ceramic substrates represent a significant advancement over traditional DBC substrates for SiC power device packaging. Their ability to overcome thermal stress, enhance bond strength, and ensure operational reliability under extreme conditions positions them as pivotal components in advancing the efficiency and performance standards of electric vehicles and other high-demand industries. As technologies evolve, optimizing brazing processes and material selections will further enhance the effectiveness and reliability of AMB substrates in diverse applications.

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