Vertical Nanoribbon Array Thermal Interface Materials
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Solution Overview
Problem
Current thermal interface materials, such as vertically aligned carbon nanotube (VACNT) arrays, fail to effectively manage heat dissipation in high power density devices due to limited areal density and contact area, leading to increased junction temperatures, degraded performance, and reliability issues.
Innovation Solution
The development of a vertically aligned graphene nanoribbon array (VERNA) is created by processing VACNT arrays to produce flat, compliant ribbon elements with enhanced packing density and contact area, achieving theoretical thermal conductance limits through anodically treating CNTs to form graphene oxide nanoribbons and subsequent reduction to remove oxygen, resulting in improved thermal conductivity and reduced interfacial resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If VACNT arrays are used as thermal interface materials, then heat transfer capability is provided, but the areal density is limited (3-10%) and contact area is insufficient, resulting in degraded thermal performance
Solution Approach 1:
The invention transforms the cylindrical geometry of carbon nanotubes into flat graphene nanoribbon geometry through controlled oxidative cleavage. This parameter change from curved to flat structure enables significantly improved packing density and areal density while maintaining the vertical alignment and heat transfer capability of the original VACNT arrays
Solution Approach 2:
The invention creates a composite structure by combining graphene oxide nanoribbons with reducing agents or through thermal treatment to produce reduced graphene oxide nanoribbons. This composite approach allows optimization of both structural packing and thermal conductivity properties
2Area of stationary object
If VACNT arrays are used, then thermal interface function is provided, but only a small fraction (10-30%) of the nanotubes are actually engaged in heat transfer due to limited contact area
Solution Approach 1:
The transformation from cylindrical nanotube geometry to flat nanoribbon geometry fundamentally changes the contact mechanics. The flat ribbons can conform to and engage with the heat generating device surface much more effectively, increasing the fraction of material actively participating in heat transfer from 10-30% to potentially near 100% engagement
Solution Approach 2:
The invention explicitly addresses the limitation of cylindrical curvature by transitioning to a flat planar structure. The flat graphene nanoribbons eliminate the curved surface problem of nanotubes, allowing maximum surface contact and engagement with the heat transfer interface
3Temperature
If VACNT arrays are used, then thermal conduction is provided, but the actual contact area with heat extraction surface is limited, causing junction temperatures to rise sharply
Solution Approach 1:
The geometric transformation to flat nanoribbons enables superior conformal contact with the heat extraction surface, dramatically increasing the effective contact area. This directly addresses the thermal bottleneck by providing larger thermal interface area to conduct heat away from the device junction
Solution Approach 2:
The graphene nanoribbon structure inherently provides flexibility and compliance, allowing the material to conform to the heat extraction surface topology. This flexible thin-film structure ensures maximum contact area engagement while maintaining the vertical heat conduction pathway
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 VERNA achieves significantly higher thermal conductivity and contact area, potentially reaching 1 GW/m2K, with a 1000-fold increase in contact area under compression, effectively addressing the limitations of VACNT arrays and enhancing heat dissipation in high power density devices.
Implementation Method 1
anodically treating the VACNT to longitudinally cleave each carbon nanotube (CNT) into a graphene oxide nanoribbon (GONR)
Implementation Method 2
cathodically polarizing the GONR array to remove oxygen resulting from the step of anodically treating the VACNT
Implementation Method 3
treating the VERNA with temperature of approximately 120 to 350 C to remove any remaining oxygen from the VERNA
Implementation Method 4
A TIM 16 is interposed between heat generating electronic devices such as chip 20 and heat sinks/exchangers 18 to facilitate heat conduction
Data Source
AI summary
A thermal interface material (TIM) and method for manufacture is disclosed. A vertically aligned carbon nanotube (VACNT) array is formed on a substrate, then individual CNTs are cleaved to form a vertical nanoribbon array (VERNA). An array of aligned, upright, flat, highly-compliant ribbon elements permit a higher packing density, better ribbon-to-ribbon engagement factor, better contact with adjoining surfaces and potentially achievement of theoretical thermal conductance limit (˜1 GW/m2K) for such nanostructured polycyclic carbon materials. Methods for forming the VERNA include either or both of electrochemical and gas phase processing steps.