Interface Optimization and Thermal Conductivity of Cu/Diamond Composites by Spark Plasma Sintering Process

At a Glance

Metadata	Details
Publication Date	2025-01-06
Journal	Nanomaterials
Authors	Jun-Feng Zhao, Hao Su, Kai Li, Haijuan Mei, Junliang Zhang
Institutions	Huizhou University
Citations	1
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Performance Cu/Diamond Composites

This document analyzes the research on optimizing the interface and thermal conductivity of Cu/Diamond (Cu/Dia) composites fabricated via Spark Plasma Sintering (SPS). The findings are leveraged to demonstrate how 6CCVD’s advanced MPCVD diamond materials and customization capabilities provide essential components for replicating and advancing this high-power thermal management technology.

Executive Summary

Application Focus: The research successfully addresses critical thermal dissipation challenges in high-power electronic devices using optimized Cu/Dia composites.
Performance Achievement: Optimization of particle size and interface chemistry resulted in a peak thermal conductivity ($\lambda$) of 516 W/m·K, representing an overall improvement of approximately 66% over the unoptimized baseline (310 W/m·K).
Material Optimization: The highest thermal performance was achieved using 200 µm diamond particles, which ensured uniform distribution and maximized relative density (95.01%).
Interface Engineering: The addition of 3 wt.% Chromium (Cr) to the Cu matrix was crucial, leading to the formation of the Cr₇C₃ carbide phase, which transitioned the interface from a weak physical bond to a strong metallurgical bond.
Processing Parameters: The optimal fabrication conditions utilized the Spark Plasma Sintering (SPS) technique at a sintering temperature of 900 °C and a pressure of 50 MPa.
Strategic Insight: The study confirms that strict control over diamond particle quality, surface morphology, and interfacial reaction layers is paramount for maximizing phonon transport efficiency in metal matrix composites.

Technical Specifications

The following hard data points were extracted from the optimization study:

Parameter	Value	Unit	Context
Peak Thermal Conductivity ($\lambda$)	516	W/m·K	Optimized composite (200 µm, 3 wt.% Cr, 900 °C)
Baseline Thermal Conductivity ($\lambda$)	310	W/m·K	Unoptimized composite (40 µm particles)
Overall Thermal Improvement	66	%	Increase from baseline to optimized state
Optimal Diamond Particle Size	200	µm	Achieves uniform distribution and highest density
Optimal Sintering Temperature	900	°C	Maximizes interface bonding strength
Sintering Pressure	50	MPa	Applied during SPS process
Diamond Volume Fraction	40	%	Used in all composite samples
Optimal Cr Alloying Content	3	wt.%	Required for metallurgical bonding
Interface Reaction Product	Cr₇C₃	N/A	Carbide phase acting as a phonon coupling layer
Relative Density (Optimal)	95.01	%	Achieved with 200 µm particles
Sample Geometry	13 x 5	mm	Diameter x Thickness of sintered cylinder

Key Methodologies

The Cu/Dia composites were fabricated using a highly controlled Spark Plasma Sintering (SPS) process, focusing on minimizing oxidation and optimizing interface formation.

Raw Material Selection:
- Matrix: Commercial purity Cu powder (99.99%).
- Reinforcement: Synthetic diamond crystal grains (tested sizes: 40 µm, 80 µm, 200 µm).
- Alloying Agent: Cr powder (tested contents: 0 wt.%, 1 wt.%, 3 wt.%).
Powder Mixing (Vacuum Planetary Ball Milling):
- Diamond, Cr, and Cu powders were weighed to achieve a 40% diamond volume fraction.
- Milling was conducted for 5 hours under vacuum to prevent Cu oxidation.
- Milling parameters: 200 rpm rotation speed, 15 min forward/15 min reverse rotation cycles.
Spark Plasma Sintering (SPS):
- Powder was pressed into a graphite mold (13 mm diameter) under an initial pressure of 50 MPa.
- Heating Profile: Sample was heated to 500 °C at a rate of 50 °C/min. Pressure was maintained while heating continued to the set sintering temperature (optimal 900 °C).
- Dwell Time: Maintained at the set temperature for 20 minutes to ensure full densification.
- Cooling: Power was turned off, and the sample cooled slowly in the furnace. Pressure was released only after the temperature dropped below 200 °C.
Characterization:
- Microstructure and elemental distribution: Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) (30 kV accelerating voltage).
- Phase identification: X-ray Diffraction (XRD) using Cu K$\alpha$ radiation.
- Thermal properties: Thermal diffusivity measured by LFA467 HyperFlash. Thermal conductivity ($\lambda$) calculated using $\lambda = a \times C_{p} \times \rho$.
- Density: Archimedes principle.

6CCVD Solutions & Capabilities

6CCVD provides the foundational MPCVD diamond materials and advanced processing services necessary to replicate and significantly enhance the thermal performance demonstrated in this research for high-power electronic packaging.

Applicable Materials for Thermal Management

The high thermal conductivity (TC) of the resulting composite is directly dependent on the quality and purity of the diamond reinforcement phase. 6CCVD offers materials optimized for extreme thermal applications:

Thermal Grade PCD Plates: Ideal precursor material for high-volume thermal management applications. We offer PCD plates up to 125 mm in diameter, which can be processed into high-purity particles (like the 200 µm size found optimal) with superior thermal properties compared to traditional synthetic diamond grains.
Optical Grade SCD (Single Crystal Diamond): For applications requiring the absolute highest thermal performance, our SCD material boasts thermal conductivity > 2000 W/m·K. This material can be used in thin-film stacks or as high-ppurity precursor material for composites, minimizing phonon scattering losses.

Customization Potential & Interface Engineering

The research highlights that interface quality (Cr₇C₃ formation) is the primary driver of the 66% thermal conductivity improvement. 6CCVD offers direct solutions to control and optimize this critical interface:

Research Requirement	6CCVD Customization Capability	Technical Advantage
Custom Dimensions (13 mm discs)	Precision Laser Cutting & Shaping	We provide custom plates and wafers in various thicknesses (SCD: 0.1 µm - 500 µm; PCD: 0.1 µm - 500 µm) and can laser cut diamond into specific geometries or process it into high-purity particle sizes (e.g., 200 µm) for SPS or infiltration methods.
Interface Alloying (Cr)	Advanced Metalization Services	While the paper used in-situ Cr alloying, 6CCVD offers pre-coating of diamond surfaces using thin-film deposition (e.g., Ti, W, Cu) prior to sintering. Pre-coating ensures uniform interfacial layers, reducing defects and enhancing the metallurgical bond strength more reliably than powder mixing alone.
High Surface Quality	Ultra-Low Roughness Polishing	Our SCD polishing achieves Ra < 1 nm, and inch-size PCD achieves Ra < 5 nm. Utilizing diamond with superior surface quality minimizes interfacial gaps and voids, directly reducing interfacial thermal resistance (r_hc) and improving overall composite density and thermal performance.
Global Supply Chain	Global Shipping (DDU/DDP)	We ensure reliable, fast delivery of high-purity diamond materials worldwide, supporting international research and manufacturing efforts.

Engineering Support

6CCVD’s in-house PhD team specializes in MPCVD diamond growth, surface science, and thermal applications. We can assist engineers and scientists with material selection, surface preparation (e.g., functionalization or metalization stack design), and optimizing diamond specifications for similar high-power electronic packaging and thermal management projects.

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

View Original Abstract

Cu/Diamond (Cu/Dia) composites are regarded as next-generation thermal dissipation materials and hold tremendous potential for use in future high-power electronic devices. The interface structure between the Cu matrix and the diamond has a significant impact on the thermophysical properties of the composite materials. In this study, Cu/Dia composite materials were fabricated using the Spark Plasma Sintering (SPS) process. The results indicate that the agglomeration of diamond particles decreases with increasing particle size and that a uniform distribution is achieved at 200 μm. With an increase in the sintering temperature, the interface bonding is first optimized and then weakened, with the optimal sintering temperature being 900 °C. The addition of Cr to the Cu matrix leads to the formation of Cr7C3 after sintering, which enhances the relative density and bonding strength at the interface, transitioning it from a physical bond to a metallurgical bond. Optimizing the diamond particle size increased the thermal conductivity from 310 W/m K to 386 W/m K, while further optimizing the interface led to a significant increase to 516 W/m K, representing an overall improvement of approximately 66%.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano15010073

References

2021 - Miniaturization of optical spectrometers [Crossref]
2020 - Printable ink design towards customizable miniaturized energy storage devices [Crossref]
2022 - A review on transient thermal management of electronic devices
2022 - Dual-functional thermal management materials for highly thermal conduction and effectively heat generation [Crossref]
2023 - Phonon thermal transport and its tunability in GaN for near-junction thermal management of electronics: A review [Crossref]
2022 - Electric-drive vehicle power electronics thermal management: Current status, challenges, and future directions [Crossref]
2024 - Review on thermal management technologies for electronics in spacecraft environment [Crossref]
2024 - Effects of various fabrication techniques on the mechanical characteristics of metal matrix composites: A review
2022 - Review on study of internal load transfer in metal matrix composites using diffraction techniques [Crossref]