Corrosion Behavior of Pressure Infiltration Diamond/Cu Composites in Neutral Salt Spray

At a Glance

Metadata	Details
Publication Date	2020-04-14
Journal	Materials
Authors	Zhongnan Xie, Hong Guo, Ximin Zhang, Shuhui Huang
Institutions	General Research Institute for Nonferrous Metals (China), State Key Laboratory of Nonferrous Metals and Processes
Citations	7
Analysis	Full AI Review Included

6CCVD Technical Documentation & Reliability Analysis: Diamond/Cu Composites in Neutral Salt Spray

Based on: “Corrosion Behavior of Pressure Infiltration Diamond/Cu Composites in Neutral Salt Spray”

Executive Summary

This study rigorously investigates the reliability of Diamond/Cu composites—critical materials for high-performance electronic packaging—when subjected to aggressive neutral salt spray (NSS) environments.

Performance Degradation: Untreated Diamond/Cu composites suffer substantial thermal performance loss (up to 22% decrease in Thermal Conductivity (TC)) after 168 hours of NSS exposure, primarily due to surface roughening and corrosion crack formation on the copper matrix.
Corrosion Mechanism: Corrosion is localized entirely within the metal matrix (copper), driven by micro-galvanic corrosion at the diamond-matrix interface. The corrosion product identified is Monoclinic Cu₂Cl(OH)₃. Diamond reinforcement particles were confirmed to be chemically inert.
Mechanical Stability: Despite severe surface corrosion, the bending strength of the composites remained highly stable, fluctuating by less than 5% relative to initial values, confirming the robustness of the diamond-matrix interface bond.
Corrosion Depth: After 168 hours of testing, localized corrosion pits reached average depths of 30-35 µm, indicating significant matrix volume loss if left unprotected.
Validation of Protection: Surface metalization (Ni/Au plating) is demonstrated as an effective strategy for achieving environmental stability, limiting the TC decrease to a negligible 1.2%-1.6% and preventing the formation of surface corrosion products entirely.
6CCVD Value Proposition: The findings emphasize the necessity of high-quality, dense diamond material combined with precision metalization for reliable thermal management devices, areas where 6CCVD offers specialized MPCVD growth and in-house coating expertise.

Technical Specifications

Parameter	Value	Unit	Context
Test Environment	5.0	wt% NaCl	Neutral Salt Spray (NSS) solution
NSS Test Temperature	35	°C	Continuous test environment
Corrosion Duration	168	hours	Maximum exposure time
Corrosion Mechanism	Micro-galvanic	-	Localized to copper matrix
Corrosion Product	Cu₂Cl(OH)₃	Monoclinic	Identified via XRD and EDS
Avg. Corrosion Depth (Untreated, 168h)	30 ± 5	µm	Depth varied by diamond vol%
TC Decay (Untreated, 60 vol%)	22	%	Total loss after 168h NSS (142.9 W/mK loss)
TC Decay (Untreated, 75 vol%)	12	%	Total loss after 168h NSS (92.8 W/mK loss)
TC Decay (Gold-Plated, 60 vol%)	1.6	%	Negligible loss after 168h NSS
TC Decay (Gold-Plated, 75 vol%)	1.2	%	Negligible loss after 168h NSS
Bending Strength Change	< 5	%	Fluctuation relative to initial value
Protective Metal Layer (Ni)	5	µm	Barrier layer thickness
Protective Metal Layer (Au)	3	µm	Outer protective layer thickness

Key Methodologies

The study utilized controlled pressure infiltration to fabricate Diamond/Cu composites and rigorous standardized testing to evaluate environmental stability.

Material Fabrication:
1. Diamond/Cu composites were prepared via pressure infiltration, melting Cu-Cr alloy onto diamond preforms.
2. Compositions studied were 60 vol% (100 µm diamond) and 75 vol% (50 µm and 400 µm mixed diamond).
Metalization Process (Anti-Corrosion Treatment):
1. Mechanically polished samples were sensitized and activated.
2. Nickel plating (5 µm thickness) was applied via electroplating at 82 °C (pH 4.5) for 20 min.
3. Gold deposition (3 µm thickness) followed at 52 °C (pH 5) for 15 min using a Di-propanedinitrile gold-based solution.
Corrosion Testing Protocol:
1. Samples were exposed to a Neutral Salt Spray (NSS) environment according to national standard GB/T 2423.17-93.
2. Corrosive medium: 5 wt% NaCl solution, pH 6.5-7.2, delivered continuously at 35 °C.
3. Corrosion rates (g/(cm²·h)) were determined by weight loss measurements after chemical de-rusting (37% AR HCl/distilled water 1:1).
Performance Characterization:
1. Corrosion Depth: Measured using a micro-area scanning electrochemical workstation (Versascan) with a 100 µm probe size.
2. Thermal Performance: Thermal diffusivity measured at room temperature using a NETZSCH LFA447 system.
3. Structure and Composition: Corrosion products characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray Diffraction (XRD).

6CCVD Solutions & Capabilities: Ensuring Reliability in Extreme Environments

The research clearly establishes that while diamond provides the inherent thermal stability and mechanical strength in composites, the component’s lifetime reliability in corrosive environments is entirely dependent on effective surface metalization. 6CCVD leverages its advanced MPCVD growth and in-house finishing capabilities to deliver materials engineered for superior reliability in demanding applications like electronic packaging and thermal management.

Applicable Materials

To replicate or extend this high-reliability thermal management research, 6CCVD provides the foundational high-purity diamond materials:

MPCVD Polycrystalline Diamond (PCD): Ideal for high-volume manufacturing of composite substrates, offering sizes up to 125mm and thicknesses up to 500 µm. Our PCD provides the extreme thermal conductivity required (>1800 W/mK) for high-power electronics.
MPCVD Single Crystal Diamond (SCD): For ultra-high purity needs or specialized applications (e.g., optical windows within packaging) requiring superior surface finish (Ra < 1nm). Available in thicknesses from 0.1 µm up to 500 µm.

Customization Potential

The study proves that the reliability of the Diamond/Cu composite is guaranteed by the robust 8 µm Ni/Au protective layer. 6CCVD is an industry leader in applying custom metal stacks directly onto our diamond substrates, providing a complete, ready-to-use solution.

Service Category	6CCVD Capability	Research Link
Custom Metalization	Full in-house capability for Au, Pt, Pd, Ti, W, and Cu metal stacks. We deliver high-adhesion layers optimized for subsequent bonding or corrosion protection.	Directly addresses the need for effective Ni/Au coating (5 µm Ni, 3 µm Au) to prevent micro-galvanic corrosion and maintain TC.
Precision Dimensions	Custom cutting services including laser processing for complex shapes and standard wafers up to 125 mm.	Allows for precise replication of the required sample geometry (e.g., 12.6 mm diameter) and integration into existing electronic packages.
Surface Finish	Advanced mechanical polishing achieving Ra < 1 nm (SCD) and Ra < 5 nm (PCD).	Crucial for minimizing surface defects where corrosion initiates (as observed in the study’s OSP scans) and ensuring optimal bonding.
Global Logistics	Global shipping options (DDU default, DDP available) ensures reliable delivery of high-value components.	Supports international research and production teams mirroring the scope of this published work.

Engineering Support

This research demonstrates that achieving optimal performance in Diamond/Cu systems requires careful material selection and rigorous interface control. 6CCVD’s in-house PhD team can assist engineers with material selection, interface design, and metalization strategies for similar Thermal Management/Heat Sink projects to guarantee both high thermal performance and environmental reliability.

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

View Original Abstract

Diamond particle-reinforced copper matrix composites (Diamond/Cu) are recognized as promising electronic packaging materials due to their excellent thermophysical properties. It is necessary to investigate the reliability of Diamond/Cu composites under extreme environmental conditions. The corrosion behavior of Diamond/Cu composites was studied in a 5 wt% NaCl neutral salt spray. Surface morphology, thermal conductivity, bending strength, corrosion rate, and corrosion depth resulting from corrosion were researched in this paper. The results showed that the corrosion phenomenon mainly occurs on the copper matrix, and the diamond and interface products do not corrode. The corrosion mechanism of Diamond/Cu composites was micro-galvanic corrosion. The corrosion product formed was Cu2Cl(OH)3. The salt spray environment had a great influence on the composite surface, but the composite properties were not significantly degenerated. After a 168-h test, the bending strength was unaltered and the thermal conductivity of gold-plated composites showed a slight decrease of 1-2%. Surface gold plating can effectively improve the surface state and thermal conductivity of Diamond/Cu composites in a salt spray environment.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma13081847

References

2004 - Thermal properties of diamond particle-dispersed Cu composites [Crossref]
2012 - Effect of copper content on the thermal conductivity and thermal expansion of Al-Cu/diamond composites [Crossref]
2014 - Low-temperature densification and excellent thermal properties of W-Cu thermal-management composites prepared from copper-coated tungsten powders [Crossref]
2016 - Effect of particle size on the thermal and mechanical properties of aluminum composites reinforced with SiC and diamond [Crossref]
2019 - Enhancing thermal conductivity of Diamond/Cu composites by regulating distribution of bimodal diamond particles [Crossref]
2011 - Interfacial microstructure and properties of diamond/Cu-xCr composites for electronic packaging applications [Crossref]
1992 - Review of corrosion studies on aluminium metal matrix composites [Crossref]
1993 - Corrosion behavior of copper-based metal-matrix composites [Crossref]
2016 - Corrosion of Aluminum Alloy Metal Matrix Composites in Neutral Chloride Solutions [Crossref]