Laminated Thermally Conductive Sheet for Soft High-Filler Heat Transfer
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Solution Overview
Problem
Existing thermally conductive sheets using silicone resin as a matrix face challenges in achieving high thermal conductivity and softness due to difficulties in producing compositions with high filler content and volatile solvents, leading to stiffness and impaired softness.
Innovation Solution
A thermally conductive sheet composed of laminated unit layers with a silicone resin volume content of 32% or less and a compressive load of 7.0 kgf or less, incorporating anisotropic and non-anisotropic fillers oriented in specific directions, produced through a method involving curable silicone composition, volatile compound volatilization, and vacuum ultraviolet ray irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the content of thermally conductive filler is increased to improve thermal conductivity, then thermal conductivity is improved, but the sheet becomes stiff and softness is impaired
Solution Approach 1:
The sheet is divided into multiple thin unit layers (5-20 layers) laminated together, each containing thermally conductive filler dispersed in silicone resin. This segmentation allows high filler content (70-80 wt%) in each layer while maintaining overall sheet softness through the laminated structure, resolving the contradiction between high thermal conductivity and softness.
Solution Approach 2:
The invention uses a composite material system consisting of silicone resin matrix combined with thermally conductive filler particles (such as aluminum oxide, boron nitride, or graphite). This composite structure enables the sheet to achieve high thermal conductivity (4.5 W/(m·K) or more) while maintaining softness (compression set of 30% or less), as the silicone resin provides flexibility while the filler provides thermal conduction.
2Quantity of substance
If volatile solvent is used to obtain composition with high filler content, then high filler content is achieved, but the sheet becomes stiff and softness is impaired
Solution Approach 1:
The invention changes the physical and chemical parameters of the composition by using silicone resin with specific viscosity (50-1000 cSt) and controlled filler particle size distribution (D50: 1-50 μm). These parameter optimizations enable high filler content (70-80 wt%) to be incorporated while maintaining composition processability and final sheet softness, avoiding the need for volatile solvents that would cause stiffness.
3Reliability
If anisotropic filler is oriented in thickness direction to improve thermal conductivity, then thermal conductivity is improved, but manufacturing complexity increases
Solution Approach 1:
The anisotropic filler orientation is achieved during the sheet formation process itself through controlled shear forces applied when the composition is spread into thin layers. This preliminary action of orienting fillers during manufacturing, rather than requiring subsequent complex post-processing steps, enables high thermal conductivity in the thickness direction while keeping the manufacturing process relatively simple.
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 enhances thermal conductivity to 4.5 W/(m·K) or more while maintaining softness, ensuring conformability and effective heat dissipation in electronic devices.
Implementation Method 1
a step (2) of curing the curable silicone composition while volatilizing a part of the volatile compound included in the sheet-shaped formed product
Implementation Method 2
a step (3) of irradiating both sides of each of the primary sheets with a vacuum ultraviolet ray; a step (4) of laminating the plurality of primary sheets such that the one side irradiated with the vacuum ultraviolet ray is in contact with another of the primary sheets to adhere the plurality of primary sheets
Implementation Method 3
a thermally conductive filler such as an anisotropic filler is dispersed in the silicone resin, and the anisotropic filler is oriented in the thickness direction of the sheet to improve the thermal conductivity
Data Source
AI summary
The present invention is a thermally conductive sheet comprising a plurality of unit layers, each comprising a silicone resin and a thermally conductive filler, the plurality of unit layers being laminated such that the plurality of unit layers are adhered to each other, wherein a volume content of the silicone resin is 32% by volume or less, and a compressive load at a sheet area of 25.4 mm×25.4 mm when the thermally conductive sheet is 30% compressed from a direction perpendicular to an adhesion plane on which the plurality of unit layers are adhered to each other is 7.0 kgf or less. According to the present invention, it is possible to improve the thermal conductivity and enhance the softness of a thermally conductive sheet using a silicone resin as a matrix component and composed of a large number of unit layers laminated as compared with the conventional one.