Thermally Conductive Silicone Composition With Creep-Resistant Coatability
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Solution Overview
Problem
Existing thermally conductive materials for electrical and electronic components face challenges in achieving both high thermal conductivity and creep resistance, with sheet-like materials having poor thermal interface performance due to high thermal contact resistance and stress issues, while thermal greases suffer from 'creeping' and inadequate heat removal when viscosity is lowered for better coating performance.
Innovation Solution
A highly thermally conductive silicone composition is developed by combining a silicon-bonded alkenyl group-containing organopolysiloxane with an organohydrogenpolysiloxane at a specific molar ratio, an inorganic filler with a specific average particle size, and a thermally conductive inorganic filler, along with a hydrolyzable organopolysiloxane, to achieve excellent creep resistance and coatability, with a thermal conductivity of at least 4 W/m.K and viscosity between 100 to 1,000 Pa.s.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the viscosity of thermal grease is lowered to achieve good coating performance, then coatability is improved, but creeping occurs due to thermal impacts
Solution Approach 1:
The invention uses a composite material system consisting of organopolysiloxane base oil combined with specific inorganic fillers (alumina, aluminum nitride, boron nitride) and silicone oil modifiers. This composite structure allows the thermal grease to maintain appropriate viscosity for coating while gaining creep resistance through the synergistic interaction of components, particularly the thickening effect of inorganic fillers and the viscosity-modifying effect of silicone oil.
Solution Approach 2:
The invention changes the physical and chemical parameters of the thermal grease by controlling the viscosity of the base oil within a specific range (10-1000 cSt at 25°C) and adjusting the content of thickening agents and viscosity modifiers. This parameter optimization allows the grease to flow properly during application while resisting creep under thermal stress during operation.
2Strength
If sheet-like materials are used to maintain form stability, then structural integrity is improved, but thermal contact resistance increases
Solution Approach 1:
The invention adopts a paste-like (grease) formulation rather than a solid sheet structure. This semi-fluid state allows the material to conform to surface irregularities and fill gaps between components, ensuring intimate thermal contact while maintaining structural integrity through its viscoelastic properties and the reinforcing effect of inorganic fillers.
3Reliability
If inorganic fillers are added to improve thermal conductivity, then thermal conductivity is improved, but viscosity increases
Solution Approach 1:
The invention optimizes the particle size distribution of inorganic fillers (combining fine particles of 0.1-3 μm with coarser particles of 3-20 μm) and controls their total content within specific ranges. This size distribution strategy improves thermal conductivity while the finer particles fill voids between larger particles, reducing void space and improving thermal pathways without excessively increasing viscosity. The base oil viscosity is also carefully selected to balance filler suspension and flowability.
Solution Approach 2:
The invention creates a composite system where inorganic fillers (alumina, aluminum nitride, boron nitride) are dispersed in an organopolysiloxane base oil matrix, with additional silicone oil modifiers and thickening agents. This composite structure allows the fillers to provide thermal conductivity while the polymer matrix and oil modifiers control the rheological properties, maintaining coatability despite the presence of high-volume filler content (30-80 wt%).
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 silicone composition effectively removes heat from electrical and electronic components with excellent creep resistance and coatability, maintaining performance during thermal cycling and long-term storage, making it suitable for thermal interface applications.
Implementation Method 1
an organopolysiloxane which is the product of (A) a silicon-bonded alkenyl group-containing organopolysiloxane reacted with (B) an organohydrogenpolysiloxane
Implementation Method 2
a thermally conductive inorganic filler having a specific average particle size... a thermal conductivity at 25°C as measured by the hot disk method... of at least 4 W/m.K
Data Source
AI summary
The purpose of the present invention is to provide a highly thermally conductive silicone composition that exhibits excellent displacement resistance and coatability by forming a silicone composition that contains: an organopolysiloxane that is a product of a reaction between (A) an organopolysiloxane having an alkenyl group bonded to a silicon atom and (B) an organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom (a Si-H group) at quantities whereby the (Si-H/Si-Vi) ratio is more than 8.0 and not more than 20.0; (C) an inorganic filler having an average particle diameter of 3 µm or less which is selected from among metal oxides and metal nitrides; and (D) a thermally conductive inorganic filler having an average particle diameter of 5 µm or more. The total amount of component (C) and component (D) is 3,500-12,000 parts by mass relative to a total of 100 parts by mass of component (A) and component (B), and the composition has a thermal conductivity of 4 W/m·K or more and an absolute viscosity of 100-1,000 Pa·s. A further purpose of the present invention is to provide a method for producing the highly thermally conductive silicone composition.