Fabrication of Functionally Graded Diamond/Al Composites by Liquid–Solid Separation Technology

At a Glance

Metadata	Details
Publication Date	2021-06-10
Journal	Materials
Authors	Hongyu Zhou, Yaqiang Li, Huimin Wang, Minrui Ran, Zhi Tong
Institutions	University of Science and Technology Beijing
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: Functionally Graded Diamond/Al Composites

Executive Summary

This analysis reviews the fabrication of Functionally Graded Diamond/Al Composites (FGMs) via Liquid-Solid Separation (LSS) technology for advanced electronic packaging shells. The core value proposition is the creation of a tailored thermal management solution that mitigates thermal stress concentration and improves component stability.

Graded Performance Achieved: A significant gradient in thermal conductivity (TC) and coefficient of thermal expansion (CTE) was successfully engineered across the shell structure, ranging from the chip interface (low CTE, high TC) to the welding interface (high CTE, high solderability).
Optimal Chip Interface: The shell bottom achieved a low CTE of 11.0 x 10^-6/K and a high TC of 169 W/m·K, ensuring excellent thermal matching and heat dissipation for microelectronic chips.
Weldable Interface: The shell wall achieved a high CTE of 19.3 x 10^-6/K, closely matching standard metal cover plates for reliable brazing/welding.
Material Composition: Diamond content was graded from 48 vol.% at the bottom to 15 vol.% at the top, correlating directly with the required thermal and mechanical properties.
Interfacial Challenge Identified: The study noted mixed interfacial bonding (diffusion-bonded and partially diffusion-bonded states), suggesting a need for enhanced surface treatment (e.g., metal coatings) to improve mechanical properties and thermal stability.
Methodology: The LSS process utilized synthetic diamond particles (106 µm) and commercial Al powder, sintered at 683 °C under 60 MPa pressure.

Technical Specifications

Parameter	Value Range	Unit	Context
Thermal Conductivity (TC)	108.25 to 169.36	W/m·K	Graded distribution (Top to Bottom)
CTE (Coefficient of Thermal Expansion)	11.0 to 19.3	10^-6/K	Graded distribution (Bottom to Top)
Diamond Content	14.69 to 48.43	vol.%	Graded distribution (Top to Bottom)
Bending Strength	88.47 to 174.72	MPa	Increases with decreasing diamond content
LSS Sintering Temperature	683	°C	Used for liquid-solid mixed-melting state
LSS Squeezing Pressure	60	MPa	Applied to fill the LSS chamber
Solidification Hold Time	240	s	Pressure held during layer-by-layer solidification
Diamond Particle Size	106	µm	Average size of MBD-4 synthetic diamond
Interdiffusion Area Width	~8	µm	Observed at the diffusion-bonded interface
Gap Area Width (Non-bonded)	~2	µm	Observed at the partially diffusion-bonded interface

Key Methodologies

The functionally graded diamond/Al composites were fabricated using an independently developed Liquid-Solid Separation (LSS) technology.

Raw Material Preparation: Commercial Al (99.81 wt.%, 37 µm average size) and MBD-4 synthetic diamond particles (106 µm average size) were mechanically mixed at a 1:4 volume ratio for 8 hours.
Billet Compression: The mixed material was compressed into a billet (48 mm x 38 mm x 7.5 mm) at 300 MPa for 1 minute.
LSS Process Setup: The billet was transferred to a custom LSS mold system and heated to the liquid-solid mixed-melting state.
Sintering Parameters: The billet was heated to 683 °C at a rate of 20 °C·min^-1.
Separation and Forming: The melt slurry was squeezed at 60 MPa using a special shape piston. The melted hot Al entered the liquid chamber through a 2 mm LSS channel, while the larger diamond particles (106 µm) were completely retained in the LSS chamber, creating the graded distribution.
Solidification: The remaining slurry solidified layer by layer under a water-cooling system, with the pressure held for 240 seconds to ensure high relative density.

6CCVD Solutions & Capabilities

The research demonstrates the critical role of diamond composites in next-generation thermal management packaging. 6CCVD is uniquely positioned to support and advance this research, particularly by addressing the interfacial bonding limitations identified in the paper.

Applicable Materials

To replicate or extend this research, 6CCVD recommends materials optimized for high-performance composite reinforcement and substrate applications:

High-Purity PCD Substrates: While the paper used synthetic diamond particles, 6CCVD can supply high-quality Polycrystalline Diamond (PCD) wafers up to 125mm in diameter and up to 500 µm thick, suitable for use as high-TC substrates or as precursors for advanced composite manufacturing techniques.
Optical Grade SCD: For applications requiring the highest thermal performance and purity, 6CCVD offers Single Crystal Diamond (SCD) plates (0.1 µm to 500 µm thick) with Ra < 1nm polishing, ensuring minimal scattering losses if optical monitoring or laser processing is involved.
Custom Diamond Precursors: 6CCVD can source or process diamond particles with specific size distributions and morphologies tailored for LSS or infiltration techniques, ensuring optimal packing fraction and flow dynamics.

Customization Potential

The paper highlights the need for near-net shape forming and improved solderability. 6CCVD directly addresses these requirements through advanced post-processing capabilities:

Research Requirement	6CCVD Capability	Technical Advantage
Improved Interfacial Bonding	Custom Metalization Services: Au, Pt, Pd, Ti, W, Cu	The paper noted that coatings (W, TiC, B₄C) are necessary to prevent Al₄C₃ formation and enhance bonding. 6CCVD offers in-house PVD/CVD metalization, including Ti and W coatings, to create robust metallurgical bonds between diamond and the Al matrix.
Near-Net Shape Forming	Custom Dimensions & Laser Cutting	6CCVD provides custom plate and wafer dimensions up to 125mm (PCD). We offer precision laser cutting services to achieve complex geometries and near-net shapes, reducing the need for extensive mechanical processing of uniform blocks.
Weldability/Solderability	Au/Pt/Ti Metal Stacks	The top wall requires high solderability. 6CCVD can apply multi-layer metal stacks (e.g., Ti/Pt/Au) to the composite surface, ensuring excellent wetting and reliable brazing with metal cover plates.
High-Density Substrates	Thick Substrates up to 10mm	6CCVD can provide diamond substrates up to 10mm thick, offering robust platforms for high-power density applications that require maximum heat spreading.

Engineering Support

The successful fabrication of FGMs requires precise control over material properties, which is 6CCVD’s core expertise. Our in-house PhD engineering team specializes in diamond material science and thermal management applications.

CTE Matching Consultation: We provide expert consultation on material selection and processing parameters to achieve precise CTE matching (e.g., 11.0 x 10^-6/K) required for sensitive microelectronic chips.
Thermal Stability Optimization: We assist researchers in selecting appropriate metalization layers and diamond grades to optimize interfacial thermal conductance, crucial for improving the thermal stability of packaging components in similar Diamond/Al Composite Packaging Shell projects.
Global Logistics: 6CCVD ensures reliable global shipping (DDU default, DDP available) for time-sensitive research projects worldwide.

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

View Original Abstract

The electronic packaging shell, the necessary material for hermetic packaging of large microelectronic device chips, is made by mechanical processing of a uniform block. However, the property variety requirements at different positions of the shell due to the performance have not been solved. An independently developed liquid-solid separation technology is applied to fabricate the diamond/Al composites with a graded distribution of diamond particles. The diamond content decreases along a gradient from the bottom of the shell, which houses the chips, to the top of the shell wall, which is welded with the cover plate. The bottom of the shell has a thermal conductivity (TC) of 169 W/mK, coefficient of thermal expansion (CTE) of 11.0 × 10−6/K, bending strength of 88 MPa, and diamond content of 48 vol.%. The top of the shell has a TC of 108 W/mK, CTE of 19.3 × 10−6/K, bending strength of 175 MPa, and diamond content of 15 vol.%, which solves the special requirements of different parts of the shell and helps to improve the thermal stability of packaging components. Moreover, the interfacial characteristics are also investigated. This work provides a promising approach for the preparation of packaging shells by near-net shape forming.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma14123205

References

2014 - Emerging challenges and materials for thermal management of electronics [Crossref]
2020 - Guiding heat in active thermal management: One-pot incorporation of interfacial nano-engineered aluminium/diamond composites into aluminium foams [Crossref]
2020 - Construction of 3D interconnected diamond networks in Al-matrix composite for high-efficiency thermal management [Crossref]
2020 - A review on fabrication methods, reinforcements and mechanical properties of aluminum matrix composites [Crossref]
2018 - The fabrication of functional gradient hypereutectic Al-Si composites by liquid-solid separation technology [Crossref]
2015 - Preparation and thermodynamic analysis of the porous ZrO2/(ZrO2 + Ni) functionally graded bolted joint [Crossref]
2016 - On the high temperature mechanical behaviors analysis of heated functionally graded plates using FEM and a new third-order shear deformation plate theory [Crossref]
2010 - Microstructure and thermal properties of Diamond-Al composite fabricated by pressureless metal infiltration [Crossref]
2019 - Interfacial products and thermal conductivity of diamond/Al composites reinforced with ZrC-coated diamond particles [Crossref]
2017 - Mo2C coating on diamond: Different effects on thermal conductivity of diamond/Al and diamond/Cu composites [Crossref]