Microstructure and finite element analysis of Mo2C-diamond/Cu composites by spark plasma sintering
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-01-01 |
| Journal | Science and Engineering of Composite Materials |
| Authors | Changrui Wang, Hongzhao Li, Wei Tian, Wenhe Liao |
| Institutions | Nanjing University of Aeronautics and Astronautics |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: MoâC-Diamond/Cu Composites for Advanced Thermal Management
Section titled âTechnical Documentation & Analysis: MoâC-Diamond/Cu Composites for Advanced Thermal ManagementâExecutive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates the fabrication of high-performance diamond/Cu composites using a molybdenum carbide (MoâC) interlayer to overcome poor diamond-copper wettability, achieving significant thermal conductivity (TC) suitable for advanced heat sink applications.
- Core Achievement: Fabrication of MoâC-coated diamond/Cu composites via Vacuum Micro-Evaporating (VME) followed by Spark Plasma Sintering (SPS).
- Optimal Performance: Achieved a peak Thermal Conductivity (TC) of 511 W/(m K) and a Relative Density (RD) of 96.13%.
- Interlayer Strategy: The MoâC layer, formed at 1,000°C for 60 min, acts as a chemically bonded interface, significantly improving adhesion between the diamond particles and the copper matrix.
- Process Optimization: Optimal SPS parameters were identified as 900°C, 80 MPa, with a short holding time of 10 min; longer sintering times were shown to damage the MoâC interlayer, reducing both RD and TC.
- Limiting Factor Identified: Finite Element Analysis (FEA) confirmed that residual porosity (4.87% optimal) and non-uniform coating distribution are the primary factors limiting the composite TC below theoretical maximums.
- 6CCVD Value Proposition: 6CCVD provides the high-purity, large-area Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) substrates necessary to achieve intrinsic diamond TC (1,500-2,000 W/(m K)), bypassing the density and interface challenges inherent in powder metallurgy composites.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental and simulation results, focusing on optimal processing conditions and resulting material properties.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Optimal Composite Thermal Conductivity (TC) | 511 | W/(m K) | Achieved via SPS (900°C, 10 min) |
| Optimal Composite Relative Density (RD) | 96.13 | % | Achieved via SPS (900°C, 10 min) |
| Optimal Sintering Temperature (SPS) | 900 | °C | For composite consolidation |
| Optimal Sintering Pressure (SPS) | 80 | MPa | For composite consolidation |
| Optimal Sintering Holding Time | 10 | min | Yielded highest RD and TC |
| Optimal MoâC Coating Temperature (VME) | 1,000 | °C | For uniform MoâC formation |
| Optimal MoâC Coating Time (VME) | 60 | min | For uniform MoâC formation |
| Theoretical MoâC Coating Thickness | 267.30 | nm | Calculated for 60 min deposition |
| Diamond Particle Size (Starting Material) | 100 | ”m | Commercially synthesized MBD-8 |
| Diamond Intrinsic TC (Reference) | 1,500 - 2,000 | W/(m K) | Theoretical maximum |
| Copper Intrinsic TC (Reference) | 398 | W/(m K) | Average TC of Cu matrix |
| Optimal Porosity (FEA Model) | 4.87 | % | Corresponding to 10 min holding time |
Key Methodologies
Section titled âKey MethodologiesâThe fabrication process involved two primary stages: MoâC coating of diamond particles and subsequent consolidation via Spark Plasma Sintering (SPS).
- Diamond Pre-Treatment:
- Commercial MBD-8 diamond particles (100 ”m) were cleaned sequentially in 10 wt% NaOH solution and 20 wt% HCl to remove oil and coarsen the surfaces.
- Particles were rinsed to neutral pH with distilled water and dried.
- MoâC Coating (Vacuum Micro-Evaporating - VME):
- Diamond particles and Mo powder (2 ”m) were mixed at a 10:1 molar ratio via planetary ball milling (300 rpm for 2h).
- The mixture was placed in a ceramic crucible inside a tube furnace (TL1200).
- The chamber was vacuumed to a pressure of â€10-3 Pa.
- The mixture was heated to the target temperature of 1,000°C and held for 60 min to ensure uniform MoâC layer formation.
- Coated particles were cleaned ultrasonically in distilled water to remove loose Mo powder and then dried.
- Composite Consolidation (Spark Plasma Sintering - SPS):
- MoâC-coated diamond particles (50 vol%) were mixed with copper powder.
- The mixture was sintered under the optimized conditions: 900°C, 80 MPa, with holding times varied (10, 20, and 40 min) to study density and TC effects.
- Characterization & Analysis:
- Microstructure was analyzed using SEM and AFM (surface roughness down to 236.4 nm peak height achieved at 1,000°C/60 min).
- Phase composition was confirmed via XRD (detecting MoâC and diamond, confirming no graphite formation at 900°C SPS).
- Thermal Conductivity (TC) was measured using laser flash apparatus (TC-7000H).
- Thermal performance was modeled using Finite Element Analysis (FEA) via Digimat and ABAQUS, incorporating porosity and coating thickness.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research highlights the critical role of the diamond-matrix interface in thermal management. While MoâC-coated powder composites achieved a respectable 511 W/(m K), 6CCVD specializes in materials that offer superior intrinsic thermal performance and integration flexibility for high-power electronics.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this research, particularly for applications requiring maximum thermal dissipation, 6CCVD recommends the following materials:
- Optical Grade Single Crystal Diamond (SCD): For applications demanding the absolute highest TC (1,800-2,000 W/(m K)) and ultra-low surface roughness (Ra < 1 nm). SCD wafers are ideal for direct integration as thin-film heat spreaders, eliminating the porosity and interface resistance issues inherent in powder composites.
- High-Purity Polycrystalline Diamond (PCD): Available in large formats (up to 125 mm diameter) and thick substrates (up to 10 mm). PCD offers excellent TC (up to 1,500 W/(m K)) at a lower cost than SCD, suitable for large-area electronic packaging and high-power modules.
- Custom Diamond Powder: While the paper used commercial powder, 6CCVD can supply high-purity, size-controlled diamond powder for specialized composite research, ensuring consistency and minimizing impurities that degrade TC.
Customization Potential
Section titled âCustomization PotentialâThe success of the MoâC interlayer demonstrates the necessity of robust chemical bonding. 6CCVD offers comprehensive services to optimize this interface for specific thermal designs:
| Research Requirement | 6CCVD Custom Capability | Technical Advantage |
|---|---|---|
| Interlayer Coating (MoâC) | Custom Metalization Services: We offer in-house deposition of refractory metals (Ti, W, Mo, Pt, Pd, Au, Cu) via PVD/CVD techniques. | Ensures precise, uniform coating thickness (critical factor identified in FEA) and superior adhesion for subsequent bonding processes (e.g., brazing or sintering). |
| Particle Size (100 ”m) | Custom Dimensions & Processing: We provide laser cutting and shaping services for SCD/PCD wafers to match specific device footprints, or supply custom-sized diamond powder. | Allows for direct integration into microelectronic devices where standard powder sizes are unsuitable, maximizing heat extraction efficiency. |
| Surface Quality (AFM/Roughness) | Precision Polishing: SCD surfaces polished to Ra < 1 nm; inch-size PCD polished to Ra < 5 nm. | Minimizes thermal boundary resistance (Kapitza resistance) when bonding diamond substrates directly to metal heat sinks or device layers. |
| Substrate Thickness | Wide Range: SCD (0.1 ”m - 500 ”m), PCD (0.1 ”m - 500 ”m), Substrates (up to 10 mm). | Provides flexibility for both thin-film device layers (e.g., GaN-on-Diamond) and robust bulk heat sinks. |
Engineering Support
Section titled âEngineering SupportâThe paper utilized sophisticated Finite Element Analysis (FEA) to model the impact of porosity and coating uniformity on TC. 6CCVDâs in-house PhD-level engineering team specializes in the thermal and mechanical properties of CVD diamond.
We offer consultation and support for similar High-Power Electronic Packaging and Heat Sink projects, assisting researchers and engineers with:
- Optimizing material selection (SCD vs. PCD vs. BDD) based on required TC, electrical properties, and cost constraints.
- Designing optimal metalization schemes (e.g., Ti/Pt/Au stacks) to minimize Kapitza resistance at the diamond-device interface.
- Providing detailed material specifications and simulation inputs (density, heat capacity, Debye sound velocity) derived from our high-purity MPCVD diamond.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Mo 2 C layer was generated on the diamond surface via vacuum micro-evaporating, which was used as the reinforcement particles to fabricate diamond/Cu composites by spark plasma sintering (SPS). The effect of evaporation parameters on the forming of Mo 2 C, and the holding time on diamond/Cu composites fabrication is studied. Combined with the experiment and finite element analysis (FEA), the holding time on diamond/Cu composites influence on the thermal conductivity (TC) of composites is further discussed. The results show that the Mo 2 C area on the diamond surface would gradually enlarge and cover the diamond surface evenly with the increment in evaporation time and temperature, better vacuum micro-evaporating parameters were given as 1,000°C for 60 min. The fractures in the diamond/Cu composites are mainly ductile fractures on copper and diamond falling out from the Mo 2 C interface. It was found that sintering time would significantly influence the dissipation property of diamond/Cu composites. A comprehensive parameter for SPS was obtained at 900°C, 80 MPa for 10 min, the relative density (RD) and TC of the composites obtained under the parameter were 96.13% and 511 W/(m K). A longer sintering time would damage the Mo 2 C interlayer and further decrease the bonding between copper matrix and diamond particles, which would lower the RD and TC of composites. It can be obtained from the comparison of simulation results and experimental results that the FEA result is closer to the experimental results due to the gaps with low heat conduction, and the air in the gaps is added in the simulation process.