Highly Filled Polymer Thermal Interface Materials
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Solution Overview
Problem
Existing thermally conductive materials for electronics face a trade-off between high thermal conductivity and low viscosity, as increased filler loading improves conductivity but raises viscosity, making it difficult to achieve high filler content while maintaining a workable consistency for needle dispensing.
Innovation Solution
A highly filled system combining coated filler particles and a compatibilizer in a polymer base, which enhances filler affinity and dispersion, allowing for extremely high filler loading while maintaining low viscosity, particularly by using a mixture of micron and nanometer-sized particles with a functional coating and a compatible polymer base.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If filler loading is increased to improve thermal conductivity, then thermal conductivity increases, but viscosity increases making the material difficult to dispense
Solution Approach 1:
The patent applies nested doll principle by using nanometer-sized filler particles to occupy the interstices between micron-sized filler particles, creating a hierarchical packing structure. This allows significantly higher total filler loading while the small particles flow into gaps without creating excessive viscosity, thus maintaining dispensability while achieving high thermal conductivity
Solution Approach 2:
The patent changes the particle size parameter by introducing a bimodal distribution with both micron and nanometer scale particles. This parameter change enables the system to achieve high filler loading with improved flow characteristics compared to monodisperse systems, as the nanoscale particles modify the rheological behavior of the composite
2Quantity of substance
If nanometer sized filler is added to increase filler loading, then filler content increases, but viscosity increases significantly
Solution Approach 1:
Nanometer-sized filler particles are nested within the interstices of micron-sized particles, maximizing space utilization. The small particles fit into gaps without creating percolation networks that would dramatically increase viscosity, enabling high filler loading while maintaining workable consistency
Solution Approach 2:
The patent introduces a compatibilizer as an intermediary substance that coats the filler particles and improves their interaction with the polymer matrix. This mediator reduces particle-particle interactions that would otherwise cause viscosity increases, allowing high nanofiller loading while maintaining low viscosity
3Reliability
If high filler loading is achieved, then thermal conductivity improves, but material becomes difficult to dispense through needle
Solution Approach 1:
The hierarchical packing of nanoscale particles within micron-scale particle gaps creates a compact structure with optimized flow properties. This nested arrangement allows the high filler loading material to maintain sufficient fluidity for needle dispensing while achieving the desired thermal conductivity
Solution Approach 2:
The patent modifies the viscosity parameter through controlled shear thinning behavior and particle size distribution optimization, enabling the material to flow easily during dispensing operations while maintaining structural integrity and high filler content in the final application
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 solution achieves a high filler loading of at least 70 volume percent with a viscosity of less than 600 Pa-s, significantly improving thermal conductivity while maintaining a workable consistency, as demonstrated by the recursive packing of micron and nanometer-sized fillers with a functional coating and a suitable compatibilizer.
Implementation Method 1
a compatibilizer which is soluble in the polymer base and comprising at least one functional moiety which interacts with the functional coating on the filler to enhance the affinity between the filler and the polymer base
Implementation Method 2
the compatibilizer... interacts with the functional coating on the filler to enhance the affinity between the filler and the polymer base, thereby improving nanometer sized filler wetting and dispersion
Implementation Method 3
said filler coated with a functional coating
Implementation Method 4
a filler comprising a mixture of micron sized particles and nanometer sized particles, the filler exhibiting a packing efficiency of at least 80%
Data Source
AI summary
A highly filled system is provided which employs the combination of coated filler particles and a compatibilizer to allow extremely high filler loading while maintaining a low viscosity. The compositions of the present invention allows a filler level which was previously unachievable due to the increase in viscosity which is particularly evident when extremely small (nanometer sized) filler is added to a system containing conventional (micron sized) filler particles. This is accomplished through selection of a coating for the filler and selection of a compatibilizer which improves the affinity between the filler and the polymer, thereby improving nanometer sized filler wetting and dispersion and allowing the filler to be incorporated into the polymer matrix.