Reasons of Green Silicon Carbide (GC) Micropowder as a Reinforcing Filler in AlSiC
1. Thermal Property Matching
Green Silicon Carbide (GC) features high thermal conductivity and a low coefficient of thermal expansion (CTE), making it highly compatible with silicon chips and aluminum nitride (AlN) ceramics. When incorporated into an AlSiC composite, it enables a combination of low thermal expansion and high thermal conductivity. This prevents issues such as significant temperature gradients, warping, and solder joint detachment during chip operation—all of which are critical requirements for electronic packaging heat-dissipation substrates. In contrast, Black Silicon Carbide contains higher impurity levels and exhibits less consistent thermal conductivity for a given particle size.
2. Purity and Impurity Control
The smelting process for Green Silicon Carbide (GC) is highly stable, resulting in lower levels of free silicon, iron, and heavy-metal impurities, with well-controlled oxygen content. Since semiconductor and optical module substrates are highly sensitive to impurities—which can lead to electrical leakage, interfacial defects, and fluctuations in thermal resistance—high-end AlSiC composites prioritize the use of Green Silicon Carbide over Black Silicon Carbide.
3. Particle Morphology Suitable for Preform Grading
Green Silicon Carbide (GC) particles possess well-defined, moderate angularity and stable morphology. When mixed in various size distributions (grading), they allow for precise control over the packing density and interconnected porosity of the preform. Uniform porosity ensures thorough infiltration by molten aluminum, resulting in high product consistency and minimizing the risk of localized aluminum voids or gas pores.
4. High-Temperature Stability and Suppression of Harmful Interfacial Reactions
Silicon Carbide (SiC) is inherently resistant to high temperatures and remains chemically stable within the temperature range used for molten aluminum infiltration (680–750°C). When combined with surface modification techniques, it helps suppress the formation of the brittle phase $Al_4C_3$, thereby enhancing the mechanical strength and the reliability of the substrate under heat and humidity.
5. Excellent Mechanical Properties
With its high hardness and high elastic modulus, Green Silicon Carbide (GC) significantly increases the rigidity and deformation resistance of the aluminum matrix. This ensures that the substrate remains dimensionally stable during packaging, reflow soldering, and long-term operational use.
6. Cost-Related Drawbacks
Green silicon carbide (GC) carries a higher cost than black silicon carbide. While some lower-end aluminum-silicon carbide (AlSiC) structural components utilize black silicon carbide to reduce costs, high-end packaging heat-dissipation substrates almost exclusively rely on green silicon carbide.
In summary, green silicon carbide (GC) micropowder offers high purity, high thermal conductivity, and a low coefficient of thermal expansion. Its particle morphology facilitates the grading process required to prepare SiC preforms. Furthermore, its low impurity content ensures a stable interface after infiltration, resulting in AlSiC substrates characterized by high thermal conductivity, low thermal expansion, and minimal defects—making them well-suited for the heat-dissipation requirements of semiconductor and optical communication chip packaging.