Silicon Nitride Plates

Semicorex Silicon nitride plates are high-performance ceramic substrates designed to perform the rigorous burden of power electronics, which offer long service life and high thermal performance performance, as technology becomes smaller and more demanding. Silicon nitride substrates are achieving popularity due to a unique combination of mechanical strength, fracture toughness, and thermal conductivity, making them an attractive substrate option in high-reliability, high-performance power modules, where conventional materials, such as alumina (Al₂O₃) or aluminum nitride (AlN), can no longer meet requirement expectations.

High fracture toughness (K₁) gives silicon nitride ceramics properties that other substrate materials do not have. These plates have a high resistance to cracking and failure damage caused by thermal cycling or cyclic load. This means that a silicon nitride plate will accommodate a significant level of mechanical and thermal stress, without damage, which increases system reliability. A result from high bending strength is the thinner cross-section of silicon nitride plates; therefore, they can weigh less and take up less space while performing at the same capability. In terms of thermal performance, silicon nitride plates act similarly to AlN with fast heat dissipation in the most extreme performance conditions.

As performance demands keep progressing, especially regarding electric and hybrid electric vehicles (xEVs), traditional ceramic materials are nearing their limitations. In instances where the chip junction temperature increases from 150 °C to 200 °C, switching losses can decrease by more than 10 %, which increases system efficiency. This thermal advantage comes with a greater demand that the thermal and mechanical reliability of substrate materials can withstand, and the structural properties of silicon nitride plates excel in these regions.

Thermal shock tolerance is another major advantage of Si₃N₄ plates. The tolerance to rapid temperature changes puts Si₃N₄ plates in an ideal position for thermal shock applications where multiple power cycling takes place. High-power density modules continuously switching devices on and off have thermally shock-loaded to extend lifetimes and minimize maintenance efforts.

The transition towards advanced packaging techniques such as solder-less assemblies and wire-bondless modules is another consideration for demanding substrate expectations. These techniques emphasize improved electrical efficiency and mechanical robustness, but thus increased demands of assembly temperature and stress tolerance on the substrate. Silicon nitride plates can fulfil  this requirement.

Aside from mechanical and thermal benefits, silicon nitride substrates are superior electrical insulators, maintaining a high dielectric strength even in elevated temperatures. This ensures the safe and reliable operation in high-voltage applications critical to the development of power electronics in automotive, industrial, and renewable energy applications.

The applications of silicon nitride plates do not stop with electric vehicles, they are also used in industrial motor drives, wind power converters, rail traction, aerospace power modules and high-end consumer electronics wherever a stable, thermally conductive and electrically insulating substrate is required.

In electric vehicle inverters, for example, high junction temperature means designers can minimize their cooling requirements, resulting in lighter weights, and maximum system efficiency, while in wind turbine converters, the relative thermal stability and mechanical reliability of silicon nitride help sustain reliable performance in the worst of environmental conditions.

Silicon nitride is a major leap in modern substrate technology over alumina or aluminium nitride, allowing thinner and lighter designs, and offering improved toughness and reliability when compared to the past, allowing engineers to develop the next generation of high-performance power modules with confidence.