Investigation of the Fabrication of Diamond/SiC Composites Using α-Si3N4/Si Infiltration

At a Glance

Metadata	Details
Publication Date	2023-09-17
Journal	Materials
Authors	Bo Xing, Yingfan Zhang, Jinzhui Zhao, Jianyu Wang, Guoqin Huang
Institutions	Huaqiao University, Zhengzhou Institute of Machinery
Citations	3
Analysis	Full AI Review Included

Technical Documentation & Analysis: Diamond/SiC Composites via Silicon Infiltration

This document analyzes the research on Diamond/SiC composite fabrication using $\alpha$-Si${3}$N${4}$/Si infiltration, focusing on material requirements and connecting them directly to 6CCVD’s advanced MPCVD diamond capabilities for high-performance thermal management applications.

Executive Summary

This study successfully optimized the fabrication of Diamond/SiC (Dia/SiC) composites, critical materials for high-power electronic packaging and heat sinks, using low-pressure vacuum silicon infiltration.

Application Focus: Dia/SiC composites exhibit high thermal conductivity and low thermal expansion, making them ideal for advanced heat dissipation in high-power density electronics.
Material Optimization: A multiscale diamond ratio optimization model (Dinger-Funk theory) was established, yielding an optimal volume ratio of 1:3:6 for D20, D50, and D90 µm diamond particles.
High Density Achieved: The optimal sample (Dia/SiC-8) achieved a maximum density of 2.73 g/cm³ and a remarkably low porosity of 0.6%.
Process Innovation: The research successfully solved the critical problem of adhesion to molten silicon by utilizing a mixed bedding powder of $\alpha$-Si${3}$N${4}$ and Si.
Synthesis Method: Composites were prepared using a two-step process: prefabricated porous preform creation followed by low-pressure vacuum siliconizing at temperatures up to 1700 °C.
Phase Composition: The final composite matrix consisted of diamond, silicon carbide (SiC), and residual elemental silicon (Si).

Technical Specifications

The following hard data points summarize the optimal material parameters and processing conditions achieved in the study:

Parameter	Value	Unit	Context
Optimal Diamond Volume Ratio	1:3:6	Ratio	D20 µm : D50 µm : D90 µm
Highest Achieved Density	2.73	g/cm³	Dia/SiC-8 sample
Lowest Achieved Porosity	0.6	%	Dia/SiC-8 sample
Optimal Sintering Temperature	1600	°C	Low-pressure siliconizing method
Maximum Sintering Temperature	1700	°C	Vacuum infiltration process
Vacuum Degree	0.01	Pa	High-temperature vacuum furnace
Bedding Powder Composition	$\alpha$-Si${3}$N${4}$ + Si	Mixture	Used to prevent adhesion to molten silicon
Si Content in Buried Powder (1700 °C)	88	%	Increased from 72% at 1500 °C

Key Methodologies

The Dia/SiC composites were fabricated using a vacuum infiltration process involving two primary steps:

Step 1: Prefabricated Porous Preform Creation
- Raw Materials: Diamond (D20, D50, D90), Silicon powder (5 µm), Graphite powder (5 µm), Phenolic Resin (binder).
- Volume Ratio (Dia/SiC Composite): Diamond:Graphite:Silicon:Resin = 40:20:20:20.
- Molding: Constant volume molding via hot pressing at 100 °C and 50 kN. Gaskets were used to control the reduction ratio (h/H) to regulate density and porosity (Dia/SiC-0 to Dia/SiC-10).
- Carbonization: Preform heated in an Argon (Ar) furnace at 1100 °C to carbonize the phenolic resin, providing initial strength and activated carbon for subsequent SiC formation.
Step 2: Vacuum Infiltration Sintering (Low-Pressure Siliconizing)
- Bedding Powder: Mixed powder of $\alpha$-Si${3}$N${4}$ and Si used to bury the preform in a graphite crucible.
- Sintering Conditions: Placed in a high-temperature vacuum furnace (ZT-40-21Y).
- Temperature Range: Low-pressure siliconizing performed between 1500 °C and 1700 °C.
- Reaction Mechanism: Elemental silicon melts and evaporates, spontaneously penetrating the porous preform under capillary pressure. Silicon reacts with carbon (from graphite and carbonized resin) to form SiC, creating a dense ceramic composite.

6CCVD Solutions & Capabilities

This research demonstrates the viability of Reaction Bonded Silicon Carbide (RBSC) methods for creating high-performance diamond composites. 6CCVD provides the foundational, high-purity diamond materials necessary to replicate this research or scale it into commercial thermal management solutions.

Applicable Materials

To replicate or extend this research, high-quality, high-pthermal conductivity diamond is essential. 6CCVD recommends the following materials:

Polycrystalline Diamond (PCD) Wafers: Ideal for large-area heat sink applications. 6CCVD offers PCD plates up to 125mm in diameter, suitable for large electronic packaging substrates.
Thermal Grade Single Crystal Diamond (SCD): For ultra-high thermal conductivity requirements (e.g., localized hot spots or high-frequency devices). SCD offers superior thermal properties compared to the industrial diamond powder used in the study.
Custom Diamond Powder: While the study used D20, D50, and D90 µm powder, 6CCVD can supply high-purity, tailored diamond powder sizes and distributions, ensuring precise adherence to Dinger-Funk optimization models for maximum packing density.

Customization Potential

The success of Dia/SiC composites relies heavily on precise geometry and interface quality. 6CCVD’s in-house engineering capabilities directly address these needs:

Research Requirement / Extension	6CCVD Capability	Technical Advantage
Large-Area Substrates	Custom dimensions up to 125mm (PCD)	Enables scaling of Dia/SiC heat sinks for commercial electronic modules.
Interface Quality	Polishing capability: Ra < 1nm (SCD), Ra < 5nm (Inch-size PCD)	Essential for minimizing thermal boundary resistance (TBR) when bonding the composite to electronic components.
Integrated Thermal Contacts	Internal metalization services (Au, Pt, Pd, Ti, W, Cu)	Allows for direct deposition of contact layers onto the diamond surface or the final Dia/SiC composite, simplifying assembly and improving thermal transfer efficiency.
Thickness Control	SCD/PCD thickness control from 0.1 µm to 500 µm	Provides flexibility for designing composites with specific thermal budgets and mechanical constraints.

Engineering Support

The optimization of particle packing and the management of high-temperature reactions (silicidation) are complex challenges. 6CCVD’s in-house PhD team specializes in MPCVD growth and material integration for high-performance thermal and electronic applications.

Thermal Management Expertise: We offer consultation on material selection and interface engineering to maximize the thermal conductivity of Dia/SiC composites, particularly when integrating high-purity SCD or large-area PCD.
Process Integration: Our team can assist researchers and engineers in selecting the optimal diamond material purity and surface preparation necessary for successful Reaction Bonded Silicon Carbide (RBSC) or Reactive Metal Infiltration (RMI) processes.

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

View Original Abstract

Diamond/SiC (Dia/SiC) composites possess excellent properties, such as high thermal conductivity and low thermal expansion coefficient. In addition, they are suitable as electronic packaging materials. This study mainly optimized the diamond particle size packing and liquid-phase silicon infiltration processes and investigated a method to prevent the adhesion of the product to molten silicon. Based on the Dinger-Funk particle stacking theory, a multiscale diamond ratio optimization model was established, and the volume ratio of diamond particles with sizes of D20, D50, and D90 was optimized as 1:3:6. The method of pressureless silicon infiltration and the formulas of the composites were investigated. The influences of bedding powder on phase composition and microstructure were studied using X-ray diffraction and scanning electron microscopy, and the optimal parameters were obtained. The porosity of the preform was controlled by regulating the feeding amount through constant volume molding. Dia/SiC-8 exhibited the highest density of 2.73 g/cm3 and the lowest porosity of 0.6%. To avoid adhesion between the sample and buried powder with the bedding silicon powder, a mixed powder of α-Si3N4 and silicon was used as the buried powder and the related mechanisms of action were discussed.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma16186252

References

2020 - In Situ Formation of Liquid Metals via Galvanic Replacement Reaction to Build Dendrite-Free Alkali-Metal-Ion Batteries [Crossref]
2017 - Homogeneous/Inhomogeneous-Structured Dielectrics and Their Energy-Storage Performances [Crossref]
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