An Investigation on the Spark Plasma Sintering Diffusion Bonding of Diamond/Cu Composites with a Cr Interlayer

At a Glance

Metadata	Details
Publication Date	2024-12-10
Journal	Materials
Authors	Ying Zhou, Daochun Hu, Minghe Chen, Taowen Wu, Jindong Ouyang
Institutions	Aviation Industry Corporation of China (China), Nanjing University of Aeronautics and Astronautics
Citations	4
Analysis	Full AI Review Included

Technical Documentation & Analysis: SPS Diffusion Bonding of Diamond/Cu Composites

This document analyzes the research paper “An Investigation on the Spark Plasma Sintering Diffusion Bonding of Diamond/Cu Composites with a Cr Interlayer” to provide technical specifications and highlight how 6CCVD’s advanced MPCVD diamond materials and services can support and extend this critical research in high-performance thermal management.

Executive Summary

This study successfully demonstrated high-quality diffusion bonding of diamond/Cu composites using Spark Plasma Sintering (SPS) and a Chromium (Cr) interlayer, achieving superior thermal and mechanical properties crucial for microelectronic heat dissipation.

Core Achievement: High-quality, defect-free diffusion bonding of diamond/Cu composites was achieved using a 10 µm Cr interlayer.
Optimal Parameters: The highest performance joint was produced under conditions of 810 °C bonding temperature, 60 minutes holding time, and 10 MPa pressure.
Thermal Performance: The resulting joint exhibited a high thermal conductivity (TC) of 700.97 W/(m·K), retaining 85.62% of the base material’s TC (818.67 W/(m·K)).
Mechanical Strength: Maximum shear strength reached 139.89 MPa, nearly doubling the strength achieved at lower temperatures (71.38 MPa at 720 °C).
Interfacial Mechanism: The Cr interlayer facilitated a strong chemical bond by reacting with diamond carbon (C) to form stable Cr₃C₂ carbides, which significantly reduced interfacial thermal resistance (acoustic mismatch).
6CCVD Relevance: This research validates the necessity of precise diamond metallization (W pre-coating) and high-quality diamond substrates, both of which are core capabilities offered by 6CCVD for advanced thermal applications.

Technical Specifications

The following hard data points were extracted from the optimal experimental conditions (10 µm Cr interlayer, 810 °C, 60 min, 10 MPa):

Parameter	Value	Unit	Context
Optimal Bonding Temperature	810	°C	Maximized atomic diffusion and carbide formation
Optimal Holding Time	60	min	Required for complete void closure
Optimal Bonding Pressure	10	MPa	Pressure for defect-free interface
Interlayer Material	Cr (99.99% purity)	N/A	Used to promote chemical affinity with diamond
Interlayer Thickness (Optimal)	10	µm	Thickness yielding highest shear strength
Resulting Thermal Conductivity (TC)	700.97	W/(m·K)	TC of the diffusion-bonded joint
Maximum Shear Strength	139.89	MPa	Mechanical strength of the joint
Base Material TC	818.67	W/(m·K)	TC of the initial diamond/Cu composite (60 vol% diamond)
Initial Diamond Metallization	100	nm	Tungsten (W) layer applied via magnetron sputtering
Key Interfacial Phases	Cr₃C₂, WC	N/A	Confirmed via XRD, responsible for chemical bonding

Key Methodologies

The SPS diffusion bonding process relied on precise material preparation and controlled thermal-mechanical parameters:

Diamond Pre-Treatment: Diamond particles within the composite were pre-metallized with a 100 nm Tungsten (W) layer via magnetron sputtering to enhance wetting and subsequent interfacial reaction.
Composite Fabrication: Diamond/Cu billets (60 vol% diamond) were created using the vacuum pressure infiltration method, serving as the base material.
SPS Setup: Samples were stacked (Diamond/Cu composite / Cr foil interlayer / Diamond/Cu composite) and placed in a graphite mold within the SPS furnace.
Heating Profile: A constant heating rate of 20 °C/min was applied, utilizing the pulsed current (Joule heating) inherent to the SPS technique.
Parameter Variation: The study systematically varied four key parameters to optimize joint quality:
- Interlayer Thickness: 10 µm, 30 µm, 50 µm.
- Bonding Temperature: 720 °C, 750 °C, 780 °C, 810 °C.
- Holding Time: 30 min, 60 min, 90 min.
- Bonding Pressure: 7.5 MPa, 10 MPa, 12.5 MPa.
Analysis: Joint quality was confirmed by SEM/EDS for microstructure and element distribution, XRD for phase identification (confirming Cr₃C₂ and WC formation), and universal tensile testing for shear strength. Thermal properties were measured using the laser flash method (LFA 467HT).

6CCVD Solutions & Capabilities

This research underscores the critical role of high-quality diamond substrates and precise metallization in achieving high-performance thermal joints. 6CCVD is uniquely positioned to supply the materials and services required to replicate, scale, and advance this technology for industrial application.

Research Requirement	6CCVD Solution & Capability	Technical Advantage for Replication/Scaling
High-Volume Diamond Substrates (For Diamond/Cu Composite Fabrication)	Polycrystalline Diamond (PCD) Plates	We supply large-format PCD wafers up to 125mm in diameter, ideal for producing large-scale, high-thermal-conductivity heat sinks and composite billets required for industrial SPS processes.
Precise Interfacial Metallization (Initial 100 nm W layer)	Custom Metalization Services (Ti, W, Cr, Cu, Au, Pt, Pd)	6CCVD offers internal, high-precision deposition of refractory metals like Tungsten (W) and Titanium (Ti). This capability ensures the formation of stable carbide layers (e.g., WC, Cr₃C₂) necessary to transition bonding from mechanical to the high-strength chemical bonding observed in this study.
Optimized Surface Quality (Minimizing voids/cracks)	Ultra-Low Roughness Polishing	Our SCD polishing achieves Ra < 1nm, and inch-size PCD achieves Ra < 5nm. Extremely flat surfaces minimize initial gaps and voids, drastically improving atomic diffusion kinetics and reducing the required SPS pressure/temperature to achieve a defect-free interface.
Custom Material Dimensions (Specific billet sizes for SPS tooling)	Custom Thickness and Dimensions	We provide SCD and PCD materials in thicknesses ranging from 0.1 µm to 500 µm, and substrates up to 10 mm. We can supply materials cut to precise specifications for specialized SPS tooling.
Advanced Interface Engineering (Cr/W/Cu interaction)	PhD-Level Engineering Support	6CCVD’s in-house team specializes in diamond-metal interface science. We offer consultation on material selection (e.g., optimizing Boron-Doped Diamond (BDD) substrates for electrochemical applications or selecting optimal interlayers like Cr or Ti for thermal management projects).

For custom specifications or material consultation regarding high-TC diamond/metal composite projects, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Spark plasma sintering (SPS) is an effective technique for studying the diffusion bonding of diamond/Cu composites, and has the potential to advance the application of copper matrix composites. This study investigates the SPS diffusion bonding of diamond/Cu composites using a chromium (Cr) interlayer. The effects of process parameters on the microstructure and mechanical properties of the bonding interface were evaluated through shear strength testing and SEM analysis. The results show that shear strength increases with interlayer thickness up to a certain point, after which it decreases. As the bonding temperature, holding time, and bonding pressure increase, defects such as cracks and voids at the diffusion-bonded interface are reduced, resulting in improved shear strength. Under suitable conditions (10 μm interlayer, 810 °C, 60 min, and 10 MPa), the bonding interface is defect-free, achieving a maximum shear strength of 139.89 MPa and a thermal conductivity (TC) of 700.97 W/(m·K), indicating high-quality diffusion bonding.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma17246026

References

2020 - Progress in heat conduction of diamond/Cu composites with high thermal conductivity
2023 - Thermal conduction and strength of diamond-copper composite sandwich obtained by SPS diffusion bonding with Ti interlayer [Crossref]
2021 - Thermal management and temperature uniformity enhancement of electronic devices by micro heat sinks: A review [Crossref]
2020 - Research progress of diamond/copper composites with high thermal conductivity [Crossref]
2022 - Research progress in interface modification and thermal conduction behavior of diamond/metal composites [Crossref]
2014 - High thermal conductive diamond/Cu-Ti composites fabricated by pressureless sintering technique [Crossref]
2018 - Optimized thermal conductivity of diamond/Cu composite prepared with tungsten-copper-coated diamond particles by vacuum sintering technique [Crossref]
2013 - Preparation of high thermal conductivity copper-diamond composites using molybdenum carbide-coated diamond particles [Crossref]
2023 - A new low-temperature preparation technology of heat-resistant diamond/Cu joint using composite braze: Microstructure evolution and mechanical properties strengthening [Crossref]