Interface engineering toward high thermal conductivity in diamond composites
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-01-01 |
| Journal | Materials Lab |
| Authors | Hailong Zhang |
| Institutions | Interface (United Kingdom) |
| Citations | 2 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis paper details advancements in interface engineering for diamond particle reinforced metal matrix composites (MMCs), positioning them as critical high-performance thermal management materials for advanced electronics.
- Core Value Proposition: MMCs (specifically Al/diamond and Cu/diamond) offer superior thermal conductivity (TC) and tailorable coefficients of thermal expansion (CTE), crucial for mitigating thermal stress and failure in high-density electronic packaging.
- Interface Challenge: The inherent poor wettability and large acoustic impedance mismatch between metal and diamond create a low interfacial thermal conductance ($G$), acting as the primary bottleneck for heat transfer.
- Key Mechanism Identified: The Acoustic Bridging Effect is suggested to surpass the bonding effect in improving TC. Bridging the vibrational mismatch (VDOS overlap) between metal and diamond is more effective than simply increasing interfacial bond strength.
- Performance Achievements: Optimized composites achieved high TCs, including 1021 W m-1 K-1 (Al/diamond) and 913 W m-1 K-1 (Cu/diamond), demonstrating significant application potential at moderate diamond content.
- Optimal Interlayer Design: The most effective strategy involves manipulating discontinuous interfacial carbides (formed via matrix alloying) to achieve high carbide coverage but small thickness, maximizing fast heat transfer channels while maintaining mechanical integrity.
- Alternative Modification Routes: Non-carbide routes, such as diamond surface oxygen termination (increasing $G$ from 23 to 165 MW m-2 K-1) and surface roughening (increasing TC by 12%), offer novel strategies for interface optimization.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Thermal Conductivity (TC) | 2200 | W m-1 K-1 | Intrinsic property of diamond reinforcement. |
| Diamond Coefficient of Thermal Expansion (CTE) | 1 x 10-6 | K-1 | Extremely low CTE, ideal for matching semiconductors (SiC, GaN). |
| Typical Metal Matrix CTE Range | 15 - 25 x 10-6 | K-1 | Range for common metals (Cu, Al), highlighting the mismatch with diamond. |
| Highest TC Achieved (Al/Diamond) | 1021 | W m-1 K-1 | Achieved with optimized discontinuous interfacial carbide. |
| Highest TC Achieved (Cu/Diamond) | 913 | W m-1 K-1 | Achieved with B-modified Cu matrix. |
| Interfacial Conductance (G) Improvement (Al/Dia) | 23 to 165 | MW m-2 K-1 | Increase achieved by modifying diamond surface with oxygen terminations. |
| Target Interfacial Carbide Thickness | < 50 | nm | Required for ultra-thin, high-performance coating; technically challenging via plating. |
| HTHP Diamond Content | ~90 | vol% | Required for high TC (~900 W m-1 K-1) using the expensive High Temperature-High Pressure method. |
Key Methodologies
Section titled âKey MethodologiesâThe primary focus of the research is on engineering the metal/diamond interface using various modification routes to enhance interfacial thermal conductance ($G$).
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Metal Matrix Alloying (In-Situ Carbide Formation):
- Carbide-forming elements (e.g., Ti, Cr, B) are alloyed into the metal matrix (Cu, Al).
- During processing, this forms a discontinuous interfacial carbide layer (e.g., TiC, B4C) consisting of metal/carbide/diamond transition zones and metal/diamond contact zones.
- Optimization Parameter: Regulating the alloying content or contact time to control carbide coverage ($s$) and thickness ($d_{carbide}$). Optimal TC is achieved with high coverage but small thickness.
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Diamond Surface Metallization (Pre-Coating):
- Diamond particles are pre-coated with carbide-forming layers (e.g., Cr3C2, TiC, WC, Mo2C) before composite fabrication.
- This route typically yields a continuous interfacial carbide layer of uniform thickness.
- Constraint: Obtaining ultra-thin (< 50 nm) coatings is technically difficult, and coatings that are too thin compromise the mechanical bonding strength.
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Diamond Surface Modification (Non-Carbide Routes):
- Oxygen Termination: Introducing oxygen terminations (C-O bonds) at the diamond surface to increase interfacial bond strength and enhance $G$ by providing additional bonding electrons to the metal.
- Surface Roughening: Treating diamond particles (e.g., using molten potassium nitrate) to increase surface roughness, thereby providing more heat transfer channels between the metal matrix and the diamond.
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High Temperature-High Pressure (HTHP) Method:
- A high-cost, high-pressure cubic-pressing technique used primarily for composites with very high diamond content (~90 vol%).
- This method effectively bypasses the poor interface issue but is limited by processing cost and scalability.
Commercial Applications
Section titled âCommercial ApplicationsâThe development of high thermal conductivity MMCs is critical for managing heat flux in modern, high-power electronic systems.
- Advanced Electronic Packaging: Used as heat sinks, substrates, and heat spreaders for high-power density devices (e.g., CPUs, GPUs, power modules).
- Semiconductor Substrates: Providing thermal management solutions for wide-bandgap semiconductor devices (SiC, GaN, GaAs) where the composite CTE can be tailored to match the semiconductor, minimizing thermal fatigue.
- Micro/Nano Manufacturing: Essential for cooling integrated circuits and transistors where shrinking size and escalating power density lead to excessive temperatures and device degradation.
- Automotive and Aerospace Power Electronics: Applications requiring lightweight, high-reliability materials capable of withstanding severe thermal cycling and high operating temperatures.
- High-Frequency/High-Speed Communication Systems: Ensuring thermal stability and longevity in RF components and high-speed data processing equipment.
View Original Abstract
Diamond particle reinforced metal matrix (metal/diamond) composites with high thermal conductivity and tailorable coefficient of thermal expansion are an ideal thermal management material for electronic packaging applications. Interface engineering is the key to designing metal/diamond composites due to large difference between metal and diamond in both chemical and physical nature. In this paper, we briefly summarize recent progress in the interface engineering of metal/diamond composites and give some perspectives on future development in this field.