Silver Diamond Composite
High-Thermal-Conductivity Ag–Si/Diamond Composites
Diamond-reinforced Ag–Si composites were developed to achieve high thermal conductivity for electronic packaging. Using gas-pressure assisted infiltration, Ag–3 wt.% Si alloy was combined with large (~340 μm) and small (~52 μm) diamond particles at total fractions of 60–79 vol.%. Thermal conductivity was measured by steady-state comparison and analyzed using a Differential Effective Medium (DEM) model.
Composites exhibited conductivities of 610–983 W/mK. The highest value, 983 W/mK, occurred at 78.6 vol.% diamond with a bimodal 4:1 large-to-small particle ratio, reflecting improved packing and reduced sensitivity to interfacial resistance. Modeling suggests that interfacial conductance (h ≈ 6.5 × 10⁷ W/m²K) critically limits performance, especially for small particles.
Predictions indicate that larger particles (>450 μm), higher-purity low-nitrogen diamond (κint ~2000 W/mK), and improved interfacial bonding (h > 1.5 × 10⁸ W/m²K) could yield conductivities exceeding 1200 W/mK, with theoretical limits near 1400 W/mK. Enhancing the Ag matrix conductivity or densification provided comparatively minor gains.
Thus, optimizing particle size, purity, and interface engineering is most effective for advancing Ag–Si/diamond composites. At ultra-high conductivities, however, thermal bottlenecks may shift from the substrate to device interfaces, emphasizing the need for integrated thermal management strategies.
Table. Thermal conductivity of Ag–Si/diamond composites (measured vs. predicted improvements)
| Composite / Condition | Diamond fraction (vol.%) | Particle size distribution | Thermal conductivity (W/mK) | Notes |
|---|---|---|---|---|
| Ag–3Si + diamond | 60–79 | Large (340 μm) / Small (52 μm) | 610 – 983 (measured) | Baseline experimental range |
| Best composition | 78.6 | 4:1 large:small | 983 (measured) | Highest achieved conductivity |
| Larger particles | ~80 | >450 μm | ~1026 (predicted) | Reduced effect of interface resistance |
| Higher-purity diamond | ~80 | Low-N, κint ~2000 W/mK | ~1132 (predicted) | Benefits from intrinsic conductivity |
| Pure Ag matrix | ~80 | Same distribution | ~1009 (predicted) | Minor improvement over Ag–3Si |
| Higher interfacial conductance | ~80 | h ≈ 1.5×10⁸ W/m²K | ~1066 (predicted) | Interface engineering |
| Particle sintering network | ~80 | Percolated diamond | >1200 (predicted) | Continuous thermal pathways |
| Combined optimization | ~80 | Large, pure, strong interface | ~1414 (predicted) | Theoretical upper bound |
SEMIXICON DIASEMI
SAN FRANCISCO 9/14/2025
#Silver Diamond # Heatsink # Highest hermal conductivity
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