Thermal Conductivity Stability of Interfacial in Situ Al4C3 Engineered Diamond/Al Composites Subjected to Thermal Cycling

At a Glance

Metadata	Details
Publication Date	2022-09-24
Journal	Materials
Authors	Ning Li, Jinpeng Hao, Yongjian Zhang, Wei Wang, Jie Zhao
Institutions	Xi’an Jiaotong University, Qilu University of Technology
Citations	17
Analysis	Full AI Review Included

Thermal Conductivity Stability of Interfacial In Situ Al₄C₃ Engineered Diamond/Al Composites

Executive Summary

This analysis focuses on the exceptional thermal stability achieved in diamond/Al composites through precise interfacial engineering, critical for high-power electronic applications.

Core Achievement: Realization of excellent Thermal Conductivity (TC) stability in diamond/Al composites subjected to 200 thermal cycles (218 K to 423 K).
Interfacial Solution: Stability is achieved by engineering a well-bonded interface using discrete in situ Aluminum Carbide (Al₄C₃) phase.
Performance Metric: The TC of the 272 µm-diamond/Al composite remained exceptionally high, over 720 W m^-1 K^-1, after 200 cycles.
Minimal Degradation: TC degradation was limited to a mild 2-5% reduction across 200 cycles, significantly better than previously reported values for similar materials.
Mechanism of Stability: The discrete Al₄C₃ phase strengthens the diamond/Al interface, reduces thermal stress concentration, and prevents the formation of interfacial gaps observed in weakly bonded systems.
TC Decline Cause: The minor TC decline is primarily attributed to the accumulation of residual plastic strain and subsequent increase in dislocation density within the soft Al matrix, which saturates after the first 50-100 cycles, leading to a TC plateau.
Interface Strength: Fracture analysis confirmed that the bonding strength of the engineered diamond/Al interface is higher than the fracture strength of the pure Al matrix.

Technical Specifications

Parameter	Value	Unit	Context
Thermal Cycling Range	218 to 423	K	JESD22-A104C H test condition
Total Thermal Cycles Tested	200	cycles	Test duration
Dwell Time (High/Low Temp)	10	min	Per temperature extreme
TC (272 µm Dia/Al, Initial)	743	W m^-1 K^-1	Before thermal cycling
TC (272 µm Dia/Al, Final)	724	W m^-1 K^-1	After 200 thermal cycles
TC Reduction (272 µm Dia/Al)	2.6	%	After 200 thermal cycles
TC Reduction (66 µm Dia/Al)	4.7	%	After 200 thermal cycles
Diamond Particle Size (Sample A)	66	µm	Reinforcement size
Diamond Particle Size (Sample B)	272	µm	Reinforcement size
Diamond Volume Fraction (66 µm)	58.2	%	Composite composition
Diamond Volume Fraction (272 µm)	59.2	%	Composite composition
Al Matrix TC (Initial, Assumed)	237	W m^-1 K^-1	Before thermal cycling
Al Matrix TC (Final, 272 µm)	222	W m^-1 K^-1	Calculated after 200 cycles (6.3% reduction)
Al₄C₃ CTE	8.0 x 10^-6	K^-1	Intermediate phase property
Maximum Calculated Plastic Strain	0.11038	-	At interface after 200 cycles

Key Methodologies

Preform Fabrication: Synthetic diamond single-crystals (66 µm and 272 µm) were densely vibrated into a graphite mold to create the diamond particle preform.
Gas Pressure Infiltration (GPI) Setup: An Al bulk (99.99 wt%) was placed atop the preform within a homemade GPI facility.
Heating and Reaction: The Al bulk was heated to 1073 K and held for 30 min to ensure melting and in situ Al₄C₃ formation at the diamond surface.
Infiltration: An Ar gas pressure of 1.0 MPa was applied for 20 min at 1073 K to infiltrate the molten Al into the diamond preform.
Thermal Cycling Test: Samples were sealed in a quartz tube under Ar gas and subjected to 200 thermal cycles (218 K to 423 K) using a thermal shock test chamber, adhering to the JESD22-A104C standard (10 min dwell time at each extreme).
Structural Characterization: Interfacial microstructure was analyzed using Scanning Transmission Electron Microscopy (STEM) and Focused Ion Beam (FIB). Fracture surfaces were examined using Field-Emission Scanning Electron Microscopy (SEM).
Thermal Property Measurement: Thermal diffusivity (a) was measured using laser flash equipment (LFA467). Thermal conductivity (λ) was calculated using the formula λ = aρC_p, where density (ρ) was measured by the Archimedes method and specific heat capacity (C_p) was derived from the rule of mixture.
Theoretical Modeling: A concentric sphere model was employed to calculate the residual plastic strain accumulation in the Al matrix during thermal cycling, correlating strain increase with TC decline.

Commercial Applications

The demonstrated high TC and exceptional thermal stability make these composites ideal candidates for demanding thermal management roles in high-reliability systems.

Electronic Packaging: Used as heat sinks and heat spreaders for high-power density modules.
High-Power Electronics: Thermal management for Insulated Gate Bipolar Transistors (IGBTs), high-frequency power amplifiers, and microwave devices.
Aerospace and Defense: Applications requiring lightweight materials with stable thermal properties under extreme temperature fluctuations.
Lightweight Vehicles: Thermal management components in electric vehicle power electronics where high TC and low specific weight are crucial.
Semiconductor Manufacturing: Substrates and carriers requiring precise temperature control and dimensional stability.

View Original Abstract

The stability of the thermal properties of diamond/Al composites during thermal cycling is crucial to their thermal management applications. In this study, we realize a well-bonded interface in diamond/Al composites by interfacial in situ Al4C3 engineering. As a result, the excellent stability of thermal conductivity in the diamond/Al composites is presented after 200 thermal cycles from 218 to 423 K. The thermal conductivity is decreased by only 2-5%, mainly in the first 50-100 thermal cycles. The reduction of thermal conductivity is ascribed to the residual plastic strain in the Al matrix after thermal cycling. Significantly, the 272 μm-diamond/Al composite maintains a thermal conductivity over 700 W m−1 K−1 after 200 thermal cycles, much higher than the reported values. The discrete in situ Al4C3 phase strengthens the diamond/Al interface and reduces the thermal stress during thermal cycling, which is responsible for the high thermal conductivity stability in the composites. The diamond/Al composites show a promising prospect for electronic packaging applications.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma15196640

References

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2016 - Effect of (0-40) wt.% Si addition to Al on the thermal conductivity and thermal expansion of diamond/Al composites by pressure infiltration [Crossref]
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Thermal Conductivity Stability of Interfacial in Situ Al4C3 Engineered Diamond/Al Composites Subjected to Thermal Cycling

At a Glance