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	State Key Laboratory of Nonferrous Metals and Processes, General Research Institute for Nonferrous Metals (China)
Citations	7
Analysis	Full AI Review Included

Executive Summary

This study investigates the reliability and corrosion behavior of Diamond particle-reinforced Copper matrix composites (Diamond/Cu), critical materials for high-performance electronic packaging, when exposed to a 5 wt% NaCl Neutral Salt Spray (NSS) environment.

Corrosion Mechanism: The primary degradation mechanism is identified as micro-galvanic corrosion, localized exclusively within the copper matrix, particularly at the diamond-matrix interface where microcracks initiate. The corrosion product is Monoclinic Cu₂Cl(OH)₃.
Performance Degradation (Untreated): Untreated Diamond/Cu composites suffered severe surface damage and significant thermal conductivity (TC) loss, decreasing by up to 22% (142.9 W/mK) for 60 vol% composites after 168 hours, primarily due to increased surface roughness and cracking.
Effectiveness of Plating: Surface metallization (Ni/Au plating) dramatically improved reliability, preventing visible corrosion products and limiting TC degradation to a negligible 1.2-1.6% over the 168-hour test period.
Mechanical Stability: The mechanical integrity of the bulk material remained stable; bending strength fluctuated by less than 5% compared to initial values, confirming that corrosion is a surface-level phenomenon that does not significantly affect bulk mechanical properties.
Corrosion Rate: The corrosion rate decreased rapidly in the initial 48 hours as corrosion products formed a protective layer, stabilizing thereafter. The average corrosion depth reached 30-35 µm after 168 hours.

Technical Specifications

Parameter	Value	Unit	Context
Max Initial Thermal Conductivity (TC)	>600	W/mK	General performance advantage
TC Decrease (Untreated, 60 vol%)	142.9 (22%)	W/mK (%)	After 168 h NSS test
TC Decrease (Gold-Plated, 75 vol%)	9.2 (1.2%)	W/mK (%)	After 168 h NSS test (Minimal degradation)
Bending Strength Fluctuation	< 5	%	Relative to initial value after 168 h NSS
Average Corrosion Depth (60 vol%)	30	µm	After 168 h NSS
Average Corrosion Depth (75 vol%)	35	µm	After 168 h NSS (More severe local corrosion)
Diamond Content Tested	60 and 75	vol%	Composites with excellent comprehensive properties
Diamond Size (60 vol%)	100	µm	Reinforcement particle size
Neutral Salt Spray (NSS) Concentration	5	wt%	NaCl solution
NSS Temperature	35	°C	Standard test condition
Ni Plating Layer Thickness	5	µm	Barrier layer in Ni-Au coating
Au Plating Layer Thickness	3	µm	Outer protective layer in Ni-Au coating
Corrosion Product Formula	Cu₂Cl(OH)₃	-	Identified via XRD and EDS

Key Methodologies

Composite Fabrication: Diamond/Cu composites were manufactured using pressure infiltration. A Cu-Cr alloy was melted and poured into diamond preforms (60 vol% and 75 vol% diamond content).
Surface Preparation: Samples were mechanically polished, cleaned with ethanol and deionized water, and then subjected to optional surface metallization.
Ni-Au Electroplating:
- Sensitization/Activation: Polished samples were treated in a sensitizing activation solution.
- Nickel Plating: Carried out at 82 °C and pH 4.5 for 20 minutes, resulting in a 5 µm Ni layer.
- Gold Deposition: Carried out at 52 °C and pH 5 for 15 minutes, using a Di-propanedinitrile gold-based solution, resulting in a 3 µm Au layer.
Neutral Salt Spray (NSS) Testing: Experiments were conducted in a sealed chamber at 35 °C, using a neutral 5 wt% NaCl solution (pH 6.5-7.2). Test durations included 16, 24, 48, 96, and 168 hours.
Corrosion Rate Determination: Corrosion products were removed using a de-rusting solution (1:1 ratio of 37% AR HCl and distilled water). The corrosion rate (g/(cm²·h)) was calculated based on weight loss (M₁ - M₂) normalized by time and the exposed copper matrix area (S).
Characterization:
- Morphology: Scanning Electron Microscopy (SEM, JSM-7610FPlus) was used to observe surface and microstructure.
- Corrosion Depth: Measured using a micro-area scanning electrochemical workstation (Versascan) with a 100 µm probe size over a 6 x 6 mm area.
- Performance: Thermal diffusivity (LFA447) and bending strength (AG-250KNIS universal testing machine) were measured before and after corrosion tests.
- Composition: Corrosion products were analyzed using X-ray Diffraction (XRD) and Energy Dispersive X-ray Spectroscopy (EDS).

Commercial Applications

The demonstrated high thermal conductivity and proven reliability of gold-plated Diamond/Cu composites in corrosive environments make them ideal for demanding thermal management applications:

High-Performance Electronic Packaging: Used as heat sinks, base plates, and thermal spreaders for high-power density devices (e.g., CPUs, GPUs, IGBT modules) where stable performance under humidity or saline exposure is required.
Aerospace and Defense: Components requiring extreme thermal stability and resistance to harsh environmental conditions, particularly in marine or coastal operational settings where salt spray is prevalent.
Semiconductor Manufacturing: Substrates for power amplifiers and microwave devices, utilizing the composite’s ability to match the thermal expansion coefficient (CTE) of semiconductor chips (like Si or GaAs) while maximizing heat dissipation.
Electric Vehicle (EV) Power Electronics: Thermal management solutions for inverters, converters, and battery cooling systems, ensuring long-term reliability against road salt and environmental moisture.
Telecommunications: Heat dissipation components for high-frequency base stations and radar systems installed outdoors or in coastal regions, where corrosion resistance is paramount for operational lifespan.

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

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