I. Aluminum vs. Diamond
With the advent of the AI computing power era, traditional thermal conduction and dissipation solutions urgently need to overcome bottlenecks-Metallic aluminum has a thermal conductivity of approximately 240 W/(m·K), significantly higher than most ceramic materials. Spherical aluminum powder can be used as a filler in thermal greases, thermal pads, or phase-change materials, applied between chips and metal heat sinks in scenarios where electrical insulation is not required or can be achieved through structural design. Diamond, on the other hand, stands out due to its exceptional thermal conductivity (approximately 2000 W/(m·K) for single crystals at room temperature) and low coefficient of thermal expansion (CTE). It is not only regarded as an important research direction but has also been developed and applied in various products, including copper (aluminum)/diamond composites, silicon carbide/diamond composites, CVD thin-film materials, nanoparticle coatings, and TIM materials incorporating diamond micro powder.
II. Problem Analysis and Solutions
A introduction to the formula "R = BLT / (λ × A)" is needed. Here, R represents thermal resistance, BLT (Bond Line Thickness) is the bond line thickness, λ is the thermal conductivity of the material, and A is the contact area. This formula intuitively shows that thermal resistance, as a measure of a material's ability to impede heat flow, is inversely proportional to thermal conductivity. BLT can be easily understood as the length of the heat conduction path, which is directly proportional to thermal resistance and therefore inversely proportional to thermal conductivity.
Undoubtedly, diamond has a higher thermal conductivity λ than aluminum. However, in practice, "the significant increase in the viscosity of silicone grease limits the filling amount of diamond powder." Researchers, engineers, and technicians in the powder industry are certainly familiar with the challenges Mr. Liu faces. Common solutions include:
1,Surface coating treatment to reduce particle interactions and enhance compatibility between the filler and the matrix, addressing issues like high surface energy causing easy agglomeration.
2,Adjusting particle morphology and particle size distribution. Spherical or spheroidal powders offer better fluidity and lower viscosity. Combining particles of different sizes allows smaller particles to fill the gaps between larger ones, forming a denser and more efficient thermally conductive network with the same or even lower total volume fraction.
3,Optimizing dispersion processes or using additives to ensure the filler powder is fully and evenly dispersed, avoiding local discontinuities that could compromise overall performance.
Beyond these methods, the construction and optimization of thermally conductive structures involve more complex and diverse material selection and combination strategies. For example, single-crystal large particles have a well-ordered structure with almost no defective grain boundaries, minimizing phonon scattering and allowing heat to transfer unimpeded through the crystal lattice. Another example is polyhedral particles, which can achieve "face-to-face contact" between crystal planes, as opposed to the "point-to-point contact" of spherical particles, significantly increasing the heat transfer area. Additionally, multi-component or multi-morphology synergies can be utilized, such as using flakes or rods (with high aspect ratios) made of the same or different materials to construct more effective thermally conductive networks.