Oleic Acid-Aligned Nanotubes in Thermal Interface Material
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Solution Overview
Problem
In three-dimensional chip stacks, heat dissipation is hindered by randomly oriented carbon nanotubes in thermal interface materials, which limits thermal conductivity due to their anisotropic nature and requires high filler loading, degrading the base matrix material's properties.
Innovation Solution
A method involving the attachment of magnetic material to carbon nanotubes, dispersion in a thermal interface material, heating to un-crosslink the polymer, and applying a magnetic field to align the nanotubes parallel to the chip surfaces, utilizing oleic acid to facilitate alignment and enhance thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If carbon nanotubes are randomly distributed in thermal interface material, then thermal conductivity is improved to some extent, but the thermal conductivity is limited due to anisotropic nature and high filler loading is required which degrades matrix material properties
Solution Approach 1:
The patent applies a magnetic field during the curing process to preliminarily align the carbon nanotubes in the thermal interface material before the matrix fully sets. This preliminary alignment action ensures that the nanotubes are oriented in the desired direction (perpendicular to chip surfaces) to maximize thermal conductivity, eliminating the need for high filler loading that would otherwise be required to achieve adequate thermal performance.
Solution Approach 2:
The patent changes the physical state parameter of the matrix material by heating it to a uncured state during which the magnetic alignment occurs, then allowing it to cure in the aligned state. This parameter change enables the nanotubes to be repositioned and aligned during the process, achieving superior thermal conductivity at lower filler concentrations compared to random distribution.
2Temperature
If high filler loading is used to achieve desired thermal conductivity, then thermal performance is improved, but the properties of the base matrix material are degraded
Solution Approach 1:
The magnetic alignment is performed preliminarily during the uncured state of the matrix, allowing nanotube orientation to be established before the matrix fully cures. This preliminary alignment enables the use of lower filler loading levels, thereby preserving the matrix material's flow, cohesion, and adhesion properties while still achieving the desired thermal conductivity.
3Temperature
If carbon nanotubes are aligned parallel to chip surfaces, then thermal conductivity is maximized, but additional processing steps are required
Solution Approach 1:
The patent merges the magnetic alignment process with the existing curing process of the thermal interface material. By applying the magnetic field during the uncured state and maintaining it through the curing process, the alignment step is combined with the material setting step, achieving nanotube orientation without adding significant process complexity.
Solution Approach 2:
The magnetic field acts as an intermediary mechanism to achieve nanotube alignment. Instead of requiring mechanical alignment methods or complex positioning fixtures, a magnetic field is used as a non-contact intermediary to orient the magnetizable nanotubes in the desired direction parallel to the chip surfaces, simplifying the overall process.
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
This approach significantly enhances thermal interface performance by aligning carbon nanotubes, improving thermal conductivity at lower filler loading levels without degrading the matrix material's properties, effectively addressing heat dissipation challenges in 3D chip stacks.
Implementation Method 1
applying a magnetic field of sufficient intensity to align the nanotubes containing a magnetic material in the thermal interface material
Implementation Method 2
a hydrophobic tail of oleic acid is wrapped around each one of the plurality of nanotubes and a hydrophilic acid head of the oleic acid is attached to the magnetic material
Implementation Method 3
heating the thermal interface material until the thermosetting polymer un-crosslinks and cooling the thermal interface material until the thermosetting polymer re-crosslinks
Implementation Method 4
a thermal interface material pad between the first chip and the second chip to conduct heat
Data Source
AI summary
The chip stack of semiconductor chips with enhanced cooling apparatus includes a first chip with circuitry on a first side and a second chip electrically and mechanically coupled to the first chip by a grid of connectors. The chip stack further includes a thermal interface material pad between the first chip and the second chip. The thermal interface material pad comprises a plurality of nanotubes containing a magnetic material, aligned parallel to mating surfaces of the first chip and the second chip, wherein a hydrophobic tail of oleic acid is wrapped around each one of the plurality of nanotubes and a hydrophilic acid head of the oleic acid is attached to the magnetic material.