Effect of Chromium Addition on the Thermal Conductivity of Cu/Diamond Composites Fabricated by SPS
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-01-01 |
| Journal | Journal of the Japan Society of Powder and Powder Metallurgy |
| Authors | Kiyoshi Mizuuchi, Kanryu Inoue, Yasuyuki Agari, Masami Sugioka, Motohiro Tanaka |
| Institutions | University of Washington, The University of Osaka |
| Citations | 8 |
| Analysis | Full AI Review Included |
Technical Analysis and Documentation for Advanced Diamond Composites
Section titled âTechnical Analysis and Documentation for Advanced Diamond CompositesâExecutive Summary
Section titled âExecutive SummaryâThis research demonstrates a highly effective methodology for significantly enhancing the thermal conductivity (TC) and mechanical strength of Copper (Cu)-Diamond composite materials, crucial for high-power thermal management applications (e.g., LSI heat sinks, advanced motor components).
- Core Achievement: Achieved a peak thermal conductivity of 584 W/mK in a (Cu-4.9 vol% Cr)-50 vol% Diamond composite via Spark Plasma Sintering (SPS).
- Mechanism: The addition of pure Chromium (Cr) powder as a third component dramatically improved the interfacial thermal boundary conductance ($h_c$) between the diamond and the Cu matrix, raising the TC by over 284% compared to composites sintered without Cr (152 W/mK).
- Interfacial Bonding: Cr presence led to strong chemical bonding, evidenced by a significant increase in bending strength (up to 180% improvement) and observation of transgranular diamond fractures rather than pure interfacial debonding.
- Methodology: Materials were densified using a rapid, low-temperature SPS recipe (1173 K, 80 MPa, 600 s hold time) suitable for preserving diamond integrity and facilitating in-situ reaction layer formation.
- 6CCVD Value Proposition: Replicating or exceeding these results requires high-purity, high-thermal-grade diamond powder, a specialization of 6CCVDâs MPCVD capabilities. Utilizing our superior diamond feedstock will maximize the compositeâs final thermal performance.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data was extracted detailing the material properties and performance achieved through Cr doping and SPS processing.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Peak Thermal Conductivity ($\lambda$) | 584 | W/mK | (Cu-4.9 vol% Cr)-50 vol% Diamond |
| Cr Concentration (Optimum TC) | 4.9 | vol% | Cr concentration in the Cu matrix |
| High TC Operating Range | 518 - 584 | W/mK | Maintained across 2.5 - 8.6 vol% Cr |
| Diamond Volume Fraction | 50 | vol% | Constant for composite samples |
| Peak Boundary Conductance ($h_c$) | $2.35 \times 10^7$ | W/m2K | Achieved at 4.9 vol% Cr (Calculated via Hasselman-Johnson Model) |
| Boundary Conductance (Baseline) | $3.59 \times 10^3$ | W/m2K | Cu/Diamond composite (No Cr) |
| Max Bending Strength (Composite) | 272 | MPa | Achieved at 9.8 vol% Cr (180% improvement over baseline) |
| Relative Sintered Density | 94.1 - 95.6 | % | Achieved for Cr-doped composites |
| Diamond Feedstock Particle Size | 310 | ”m | Hydrostatic pressure synthesized (HPHT) |
Key Methodologies
Section titled âKey MethodologiesâThe Cu/Diamond composites were successfully consolidated using the Spark Plasma Sintering (SPS) technique, ensuring rapid densification while limiting diamond degradation.
The specific processing recipe parameters were:
- Raw Materials Preparation: Mixtures consisted of Diamond powder (310 ”m, filler), Cu powder (<45 ”m, matrix), and Cr powder (<45 ”m, dopant).
- Mixing Ratio: Composite samples were prepared with a fixed 50 vol% Diamond. The remaining Cu-Cr matrix ratio was varied, targeting Cr concentrations in the matrix from 0 to 9.8 vol%.
- Sintering Atmosphere: Processing was conducted under a high vacuum environment (2 Pa).
- Pressure Application: A uniaxial pressure of 80 MPa was applied during the entire heating and holding phase.
- Heating Profile:
- Heating Rate: 1.67 K/s.
- Peak Sintering Temperature: 1173 K (900 °C).
- Dwell Time: The samples were held at the peak temperature for 600 seconds (10 minutes).
- Characterization: Thermal conductivity was measured using the laser flash method (NETZSCH-LFA457). Microstructure and phase identification were performed using SEM/EDX and X-ray diffraction (XRD).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis study highlights the critical importance of diamond quality and robust interfacial bonding ($h_c$) for achieving high-performance thermal management materials. 6CCVD provides the superior MPCVD diamond feedstock and engineering services required to optimize and commercialize this promising technology.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate the demonstrated TC enhancement and push performance beyond the 584 W/mK achieved using industrial HPHT powder, researchers should transition to CVD-grown diamond.
| 6CCVD Material Grade | Description & Relevance | Optimization Opportunity |
|---|---|---|
| High Thermal Grade PCD | Polycrystalline Diamond (PCD) grown via MPCVD. Provides extremely high intrinsic thermal conductivity (up to 2000 W/mK). | Utilize PCD feedstock powder with controlled grain sizes to achieve better matrix packing and higher intrinsic thermal transport capacity than the 310 ”m HPHT diamond used in the paper. |
| Optical Grade SCD | Single Crystal Diamond (SCD) material, offering the highest thermal purity and stability. | If the end application requires specific facet orientations or ultimate purity for precise in-situ reaction layer control, SCD provides unmatched uniformity and chemical consistency. |
| Custom Substrates/Plates | SCD/PCD wafers available up to 125 mm diameter, with thicknesses up to 10 mm. | Provide large-area, polished plates ready for subsequent SPS consolidation into industrial-scale Cu-Diamond thermal layers. |
Customization Potential
Section titled âCustomization PotentialâThe success of the Cr addition hinges on precise particle selection, surface preparation, and final geometry. 6CCVD supports every stage of the development process:
- Custom Dimensions and Geometry: While the paper used small 10 mm discs, 6CCVD manufactures plates/wafers up to 125 mm (PCD). We offer advanced laser cutting and machining services to produce complex shapes and precise geometries required for modern electronic packaging.
- Ultra-Smooth Polishing: For applications requiring subsequent deposition or bonding, 6CCVD guarantees ultra-smooth surfaces: Ra < 1 nm (SCD) and Ra < 5 nm (Inch-size PCD).
- Advanced Metalization Stacks: If the composite requires further integration layers (e.g., diffusion barriers or solder-wettable surfaces), 6CCVD offers in-house deposition of standard and custom metal stacks, including Au, Pt, Pd, Ti, W, and Cu. This eliminates external processing risks and ensures maximum material compatibility.
Engineering Support
Section titled âEngineering SupportâThis research indicates that the key barrier to thermal performance in metal matrix composites is the interface (the $h_c$ factor), rather than the bulk material properties alone. Our in-house PhD team specializes in CVD diamond surface science and interfacial design.
- 6CCVDâs experts can assist with material selection and specification for projects targeting high thermal dissipation in LSI chips, high-flux LEDs, and next-generation electric motor components.
- We provide consultation on optimizing diamond particle size distribution and surface termination to further enhance reactivity with third-party dopants like Cr during SPS, aiming to achieve $\lambda$ values significantly greater than 584 W/mK.
Call to Action
Section titled âCall to ActionâTo drive the next generation of high-performance thermal management solutions by leveraging superior MPCVD diamond feedstock and custom processing, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available).
View Original Abstract
Diamond-particle-dispersed-copper (Cu) matrix composites were fabricated by spark plasma sintering (SPS) process from the mixture of diamond particles, pure-Cu and chromium (Cr) powders. The microstructures and the thermal conductivities of the composites fabricated were examined. These composites were all well consolidated at a temperature of 1173 K for 600 s by SPS process. No reaction at the interface between the diamond particle and the Cu matrix was observed by scanning electron microscopy and X-ray diffraction analysis for the composites fabricated under the sintering conditions employed in the present study. The relative packing density of the diamond particle dispersed Cu matrix composites with Cr addition was 4.45.9 % higher than that without Cr addition. The thermal conductivity of the Cu/diamond composite drastically increased with Cr addition. The thermal conductivity of (Cu-Cr)-50 vol% diamond composites was 518584 W/mK in a volume fraction range of Cr between 2.5 and 8.6 vol% in Cu matrix. Numerous transgranular fractures of diamond particles were observed on the bending fracture surface of diamond particle dispersed Cu matrix composites with Cr addition, indicating strong bonding between the diamond particle and the Cu matrix in the composite.