RETRACTED - Cr–Diamond/Cu Composites with High Thermal Conductivity Fabricated by Vacuum Hot Pressing

At a Glance

Metadata	Details
Publication Date	2024-07-26
Journal	Materials
Authors	Q. Xu, Xiaodie Cao, Yibo Liu, Yanjun Xu, Jiajun Wu
Institutions	Shantou University, China Iron and Steel Research Institute Group
Citations	5
Analysis	Full AI Review Included

Technical Analysis and Documentation: Cr-Diamond/Cu Composites for High-Performance Thermal Management

Executive Summary

This analysis focuses on the synthesis and characterization of Chromium-plated diamond/copper (Cr-Diamond/Cu) composites fabricated via Vacuum Hot Pressing (VHP) for high-power electronic heat dissipation. The key findings and commercial implications are summarized below:

High Thermal Performance: The composite achieved a maximum thermal conductivity (TC) of 593.67 W·m^-1·K^-1, significantly exceeding conventional electronic packaging materials (< 400 W·m^-1·K^-1).
Interfacial Engineering Success: The introduction of a Chromium (Cr) coating on the diamond particles resulted in a 266% increase in TC compared to unplated diamond/Cu composites.
Carbide Layer Mechanism: Enhanced thermal transport is attributed to the formation of a stable Chromium Carbide (Cr₃C₂) interfacial layer, approximately 650 nm thick, which creates a mechanical “pinning effect” and minimizes interfacial thermal resistance (ITR).
Process Validation: Vacuum Hot Pressing (VHP) at 1050 °C and 20 MPa is confirmed as a viable, cost-effective, and scalable method for producing high-volume-fraction diamond composites.
Application Focus: The resulting material meets the stringent thermal requirements for high-power semiconductor components, heat sinks, and thermal interface materials (TIMs) in consumer electronics, aerospace, and defense sectors.

Technical Specifications

The following hard data points were extracted from the experimental results, focusing on optimal performance parameters:

Parameter	Value	Unit	Context
Maximum Thermal Conductivity (TC)	593.67	W·m^-1·K^-1	Achieved at 1050 °C, 20 MPa
TC Improvement (Optimal Cr Layer)	266	%	Relative to unplated diamond/Cu
Optimal Cr Layer Thickness	150	nm	Yielded highest TC
Optimal Diamond Particle Size	210	µm	70/80 mesh
Optimal Sintering Temperature	1050	°C	For maximum TC
Optimal Sintering Pressure	20	MPa	For maximum TC
Interfacial Carbide Phase	Cr₃C₂	N/A	Confirmed by XRD analysis
Interfacial Layer Thickness	650	nm	Measured via EDS line scan
Interfacial Thermal Resistance (ITR)	3.94 x 10^-8	m²·K·W^-1	Calculated value for Cr-plated interface
Maximum Composite Density	5.58	g·cm^-3	Achieved at 1050 °C, 25 MPa
Thermal Expansion Coefficient (CTE) Range	6.37 to 8.42 x 10^-6	K^-1	Measured across 25 °C to 300 °C

Key Methodologies

The Cr-Diamond/Cu composites were prepared using a controlled Vacuum Hot Pressing (VHP) powder metallurgy process, emphasizing precise control over the diamond reinforcement and interfacial layer formation.

Material Selection:
- Reinforcement: MBD6 artificial diamond particles were used in three size ranges (38 µm-45 µm, 75 µm-90 µm, and 180 µm-212 µm).
- Matrix: Electrolytic copper powder (99.9 wt%) with a 35 µm particle size.
Interface Modification: Diamond particles were pre-plated with Chromium (Cr) layers of controlled thicknesses (150 nm and 200 nm) to promote chemical reaction.
Mixing and Compaction: Weighed copper and diamond powders were mixed and loaded into a graphite mold.
Vacuum Hot Pressing (VHP):
- The mold was placed in a vacuum-protected atmosphere sintering furnace.
- The chamber was evacuated to a pressure below 101 Pa.
- Sintering Parameters: Temperature varied from 850 °C to 1100 °C; pressure varied from 20 MPa to 30 MPa; holding time was fixed at 30 min.
Cooling Protocol: Pressure was maintained for an additional 60 min during the cooling phase to mitigate interface shrinkage and reduce pore formation.
Characterization:
- Microstructure and fracture morphology were analyzed using Field-Emission Scanning Electron Microscopy (FE-SEM).
- Interface composition and layer thickness were determined via X-ray Energy-Dispersive Spectroscopy (EDS) line scans.
- Phase composition (Cr₃C₂) was confirmed using X-ray Diffraction (XRD).
- Thermal diffusivity and specific heat capacity were measured using the Laser Flash Apparatus (LFA).

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the high-quality CVD diamond materials and advanced metalization services required to replicate and extend this high-performance thermal management research. Our capabilities ensure superior material purity and precise engineering control, critical for minimizing ITR and maximizing composite TC.

Applicable Materials

To replicate or extend this high-performance thermal management research, 6CCVD recommends leveraging our superior CVD diamond materials:

High-Purity Polycrystalline Diamond (PCD) Wafers:
- Ideal for use as high-quality, dense substrates or as the primary reinforcement material in composite matrices.
- Available in custom dimensions up to 125mm diameter and thicknesses up to 500 µm.
Single Crystal Diamond (SCD) Plates:
- For fundamental research requiring the highest intrinsic thermal conductivity (up to 2000 W·m^-1·K^-1) and ultra-low surface roughness (Ra < 1nm).
- Available in thicknesses from 0.1 µm to 500 µm.
Custom CVD Diamond Powder:
- 6CCVD can supply high-purity CVD diamond material tailored for crushing into specific particle sizes (e.g., 70/80 mesh, 180 µm-212 µm) to ensure maximum intrinsic thermal performance in the final composite, surpassing the quality of standard MBD6 artificial diamond.

Customization Potential

The success of the Cr-Diamond/Cu composite relies heavily on precise interfacial engineering. 6CCVD offers comprehensive in-house services to meet these exact specifications:

Service	6CCVD Capability	Relevance to Research
Metalization	In-house deposition of Au, Pt, Pd, Ti, W, Cu, and Cr (as required by the paper).	We provide precise control over carbide-forming element thickness (e.g., 150 nm to 650 nm) to optimize the formation of low-ITR phases like Cr₃C₂ or TiC.
Custom Dimensions	Plates and wafers available up to 125mm (PCD) and substrates up to 10mm thick.	Supports large-scale VHP or SPS manufacturing processes and provides custom sample sizes for thermal testing (LFA).
Surface Finish	Polishing to achieve Ra < 1nm (SCD) and Ra < 5nm (Inch-size PCD).	Ensures optimal surface preparation for uniform metal coating adhesion and subsequent composite consolidation.
Doping	Boron-Doped Diamond (BDD) available.	Useful for extending research into electrochemistry or semiconductor applications requiring conductive diamond composites.

Engineering Support

6CCVD’s in-house PhD team specializes in optimizing CVD diamond properties for extreme thermal and mechanical applications. We offer consultative support for:

Interface Optimization: Assistance in selecting and modeling the optimal carbide interlayer (Cr, Ti, W) to minimize phonon scattering and ITR for specific High-Power Electronic Thermal Management projects (e.g., heat sinks, TIMs).
Process Integration: Guidance on integrating high-quality CVD diamond materials into powder metallurgy techniques like VHP and SPS to achieve high density and compactness (> 97.8%).
Global Logistics: Global shipping is available (DDU default, DDP available) to ensure timely delivery of custom materials worldwide.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Chromium-plated diamond/copper composite materials, with Cr layer thicknesses of 150 nm and 200 nm, were synthesized using a vacuum hot-press sintering process. Comparative analysis revealed that the thermal conductivity of the composite material with a Cr layer thickness of 150 nm increased by 266%, while that with a Cr layer thickness of 200 nm increased by 242%, relative to the diamond/copper composite materials without Cr plating. This indicates that the introduction of the Cr layer significantly enhanced the thermal conductivity of the composite material. The thermal properties of the composite material initially increased and subsequently decreased with rising sintering temperature. At a sintering temperature of 1050 °C and a diamond particle size of 210 μm, the thermal conductivity of the chromium-plated diamond/copper composite material reached a maximum value of 593.67 W∙m−1∙K−1. This high thermal conductivity is attributed to the formation of chromium carbide at the interface. Additionally, the surface of the diamond particles in contact with the carbide layer exhibited a continuous serrated morphology due to the interface reaction. This “pinning effect” at the interface strengthened the bonding between the diamond particles and the copper matrix, thereby enhancing the overall thermal conductivity of the composite material.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma17153711

References

2020 - Fabrication of high thermal conductivity copper/diamond composites by electrodeposition under potentiostatic conditions [Crossref]
2019 - Effect of titanium and zirconium carbide interphases on the thermal conductivity and interfacial heat transfers in copper/diamond composite materials [Crossref]
2008 - Diamond as an electronic material [Crossref]
2019 - Interfacial structure evolution and thermal conductivity of Cu-Zr/diamond composites prepared by gas pressure infiltration [Crossref]
2019 - Effect of tungsten based coating characteristics on microstructure and thermal conductivity of diamond/Cu composites prepared by pressueless infiltration [Crossref]
2017 - Formation of Cu nanodots on diamond surface to improve heat transfer in Cu/D composites [Crossref]
2018 - Structure and thermal properties of layered Ti-clad diamond/Cu composites prepared by SPS and HP [Crossref]
2024 - Effects of Diamond Content on the Thermal Conductivity of Copper Matrix Composite Materials Prepared by Cold Spraying [Crossref]
2023 - Analysis of the effect of interfacial thermal conductivity on the thermal conductivity of copper/diamond composites