Multilayer CNT Thermal Interface Structures for Lower Thermal Resistance
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Solution Overview
Problem
The challenge in growing long carbon nanotube (CNT) arrays on metal substrates is due to subsurface diffusion of the catalyst and accumulation of defects, leading to reduced thermal conductivity and efficiency in thermal interface materials (TIMs).
Innovation Solution
The solution involves stacking multiple vertically aligned CNT arrays to form multilayered or multitiered structures, where the nanostructure elements interdigitate, effectively increasing the density of CNTs and reducing thermal resistance. This approach mitigates the adverse effects of thickness and boundaries on energy transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CNT arrays are grown on metal substrates to eliminate pump out and voiding issues, then reliability is improved, but manufacturing precision deteriorates due to catalyst subsurface diffusion and defect accumulation
Solution Approach 1:
The invention divides the CNT array structure into multiple separate layers grown on individual metal substrates. Each layer can be grown and optimized independently, then stacked together. This segmentation allows each layer to achieve better growth quality while maintaining the overall reliability benefits of metal substrate growth, resolving the contradiction between reliability improvement and manufacturing precision deterioration.
Solution Approach 2:
The invention creates a composite structure by stacking multiple CNT array layers on metal substrates. This composite approach combines the advantages of metal substrate growth (eliminating pump out and voiding) with the ability to control each layer's quality independently, thereby maintaining both reliability and manufacturing precision.
2Temperature
If CNT length is increased to improve thermal conductance, then heat transfer efficiency is improved, but manufacturing precision deteriorates due to defect accumulation
Solution Approach 1:
Instead of growing one extremely long CNT layer, the invention segments the thermal transport path into multiple shorter CNT layers stacked together. Each layer can be grown with controlled length and fewer defects, yet the stack achieves comparable or superior overall thermal conductance through the cumulative effect of multiple high-quality layers.
Solution Approach 2:
The invention changes the structural parameter from a single long CNT layer to multiple shorter layers. This parameter change allows optimization of each layer's growth conditions to minimize defects while maintaining the total thickness and thermal conductance required for effective heat transfer.
3Temperature
If multiple CNT arrays are stacked to increase CNT density and reduce thermal resistance, then thermal conductance is improved, but device complexity increases
Solution Approach 1:
The invention merges multiple identical or similar CNT array structures into a stacked configuration. Rather than creating a complex single-layer structure, it combines several simpler layers, each with the same relatively simple architecture, to achieve the desired high CNT density and reduced thermal resistance while keeping individual layer complexity low.
4Temperature
If CNT array thickness is increased to improve thermal transport, then thermal conductance is improved, but thermal resistance increases linearly as in traditional materials
Solution Approach 1:
The invention transitions from a single-plane thermal transport structure to a multi-layer stacked structure, effectively adding the vertical dimension of layer stacking. This dimensional change allows heat to travel through multiple parallel pathways across the layers, reducing the effective thermal resistance per unit thickness and breaking the linear relationship between thickness and thermal resistance seen in traditional materials.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The multilayered structures exhibit enhanced thermal conductance and mechanical durability, making them suitable as thermal interface materials for applications requiring efficient heat transfer, such as in electronic devices. The interdigitated structure minimizes thermal resistance and maintains compliance, allowing for effective contact with varying surfaces.
Implementation Method 1
The high in-plane conductivity of individual nanotubes (as high as 3,000 W/m-K) means that even at relatively low CNT densities (typical CNT fill factors are on the order of 1%) the cross plane thermal conductance of a CNT-based TIM can be competitive with that of thermal grease.
Implementation Method 2
the favorable deformation mechanics of CNTs allow them to efficiently conform to the asperities of adjoining surfaces, resulting in high contact areas at such interfaces between surfaces
Implementation Method 3
the resulting multilayered structures can mitigate the adverse impact of thickness and boundaries on energy transport as a result of the interdigitation of the nanostructure elements (i.e., CNTs) of the two or more arrays when contacted
Data Source
AI summary
Multilayered or multitiered structures formed by stacking of vertically aligned carbon nanotube (CNT) arrays and methods of making and using thereof are described herein. Such multilayered or multitiered structures can be used as thermal interface materials (TIMs).