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

Disclaimer: This analysis is based on a research paper that has been officially RETRACTED by the publisher (Materials 2024, 17, 6013). Engineers should treat the data and conclusions presented herein as potentially unreliable or invalid.

Executive Summary

This study investigated the fabrication and thermal performance of Chromium-plated diamond/Copper (Cr-Diamond/Cu) composites using Vacuum Hot Pressing (VHP) for high-power thermal management applications.

Core Achievement: A maximum thermal conductivity (TC) of 593.67 W·m^-1·K^-1 was achieved in the Cr-Diamond/Cu composite.
Performance Enhancement: The introduction of a Cr interface layer increased the TC by 266% compared to unplated diamond/copper composites under similar conditions.
Optimal Processing: Maximum TC was obtained at a sintering temperature of 1050 °C and a pressure of 20 MPa, using 210 µm diamond particles.
Interface Mechanism: The Cr coating reacted with the diamond surface to form a Chromium Carbide (Cr₃C₂) transition layer, approximately 650 nm thick.
Bonding Improvement: This carbide layer created a “pinning effect” (serrated morphology) at the interface, significantly strengthening the metallurgical bond and reducing interfacial thermal resistance (R_int).
Thermal Stability: The TC of the composites decreased as the operating temperature increased (298 K to 573 K), but remained high (400-500 W·m^-1·K^-1 at 300 °C), meeting requirements for high-power electronic packaging.

Technical Specifications

Parameter	Value	Unit	Context
Maximum Thermal Conductivity (TC)	593.67	W·m^-1·K^-1	Optimal conditions: 1050 °C, 20 MPa, 210 µm diamond
TC Improvement (Cr vs. Bare)	266	%	150 nm Cr layer vs. unplated composite (850 °C)
Interfacial Thermal Resistance (R_int)	3.94 x 10^-8	m²·K·W^-1	Calculated value for Cr-plated composite
Carbide Interface Thickness	~650	nm	Measured via EDS line scan
Primary Interface Phase	Cr₃C₂	Chemical Formula	Confirmed by XRD analysis
Optimal Sintering Temperature	1050	°C	Yielded maximum TC
Optimal Sintering Pressure	20	MPa	Yielded maximum TC
Maximum Compactness	97.8	%	Achieved at 1050 °C, 25 MPa
Diamond Particle Size Range	38 to 212	µm	Reinforcement material range
Copper Powder Particle Size	35	µm	Matrix material
Average CTE (25-300 °C)	7.92 to 8.42	x 10^-6 K^-1	Range for optimal samples

Key Methodologies

The Cr-Diamond/Cu composites were prepared using a Vacuum Hot Pressing (VHP) process (ZM-34-10 furnace).

Material Preparation:
- Reinforcement: MBD6 artificial diamond particles (38-212 µm) were used, either bare or pre-plated with Cr layers (150 nm or 200 nm thickness).
- Matrix: Electrolytic copper powder (99.9 wt%, 35 µm, dendritic shape).
- Mixing: Weighed copper powder and diamond particles were mixed thoroughly.
Sintering Setup:
- The mixed powder was loaded into a graphite mold, smoothed, and compacted.
- The mold was placed on the lifting platform of the VHP furnace.
Vacuum Hot Pressing (VHP) Parameters:
- Vacuum: Furnace chamber evacuated to below 101 Pa.
- Temperature Range: 850 °C to 1100 °C (Optimal TC at 1050 °C).
- Pressure Range: 20 MPa to 30 MPa (Optimal TC at 20 MPa).
- Holding Time: 30 minutes.
Cooling and Post-Processing:
- After heating stopped, pressure was maintained for 60 minutes to reduce interface shrinkage pores during cooling.
- The sample was cooled to room temperature inside the furnace.
Characterization:
- Microstructure/Morphology: FEI Nova nanoSEM450 (SEM).
- Element Distribution/Interface: X-Max50 EDS analyzer.
- Phase Composition: X-ray diffraction (XRD) (confirmed Cr₃C₂).
- Thermal Diffusivity (α): NETZSCH LFA457 laser flash apparatus.
- Thermal Expansion (CTE): NETZSCH DIL 402SU dilatometer.

Commercial Applications

The high thermal conductivity and controlled thermal expansion coefficient (CTE) of Cr-Diamond/Cu composites make them highly suitable for advanced thermal management solutions in high-power density systems.

Electronics Thermal Management:
- Heat Sinks and Heat Spreaders for CPUs and GPUs.
- Thermal Interface Materials (TIMs) in high-power electronic devices.
- Packaging for high-integration semiconductor chips and modules.
Power Electronics:
- Substrates for GaN-based power devices requiring efficient heat dissipation.
High-Tech Sectors:
- Aerospace and Defense components (e.g., thermal shields, heat spreaders) where low weight, high TC, and mechanical strength are critical.
Tooling:
- Potential application in tool-grade composites (drills, saw blades) where mechanical properties are also important, though the study focused on high volume fraction materials (60 vol.%).

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