Thermally Conductive Silicone Composition with Segmented Filler Sizes
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Solution Overview
Problem
Conventional thermally conductive compositions struggle to simultaneously achieve an extrusion rate of greater than 60 g/min and a thermal conductivity of at least 9.0 W/m*K, as increasing filler content for conductivity often results in high viscosity, inhibiting extrusion rate and usability.
Innovation Solution
A thermally conductive composition comprising a curable silicone composition with a specific blend of aluminum nitride fillers, spherical aluminum oxide particles, and irregular zinc oxide particles, along with a filler treating agent, to achieve the desired extrusion rate and thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the amount of thermally conductive filler is increased to increase thermal conductivity, then thermal conductivity is improved, but viscosity increases which inhibits extrusion rate and dispensing performance
Solution Approach 1:
The aluminum nitride filler is segmented into multiple particle sizes (10-45 μm range with specific distribution). This size segmentation allows smaller particles to fill voids between larger particles, improving thermal conductivity without proportionally increasing viscosity, thus resolving the contradiction between thermal performance and extrusability
Solution Approach 2:
The patent applies local quality by using a filler treating agent specifically on the filler particles to modify their surface properties. This localized treatment reduces inter-particle friction and viscosity enhancement, allowing high filler loading for thermal conductivity while maintaining acceptable extrusion rates
2Temperature
If boron nitride filler is added at concentrations of 5 weight-percent or more to achieve thermal conductivity of 9.0 W/m*K, then thermal conductivity is improved, but viscosity becomes too high to achieve extrusion rate greater than 60 g/min
Solution Approach 1:
The patent changes the particle size parameter of the aluminum nitride filler to a specific distribution (D10=15-25 μm, D50=30-40 μm, D90=45-65 μm) and combines it with filler treating agent. This parameter optimization achieves the required thermal conductivity with lower total filler loading, maintaining extrusion rate above 60 g/min
Solution Approach 2:
The patent creates a composite filler system combining aluminum nitride (primary thermal conductor) with the filler treating agent (surface modifier). This composite approach provides thermal conductivity enhancement while the treating agent component reduces viscosity penalties, enabling both high thermal conductivity and acceptable extrusion rates
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 composition achieves an extrusion rate of greater than 60 g/min and a thermal conductivity of at least 9.0 W/m*K, making it suitable for use as a thermal interface material in electronic devices.
Implementation Method 1
The thermally conductive composition contains from 40 weight-percent to 55 weight-percent of aluminum nitride fillers which provide thermal conductivity
Implementation Method 2
a curable organopolysiloxane comprising: (a1) a vinyldimethylsiloxy-terminated polydimethylpolysiloxane, (a2) a silicon-hydride functional crosslinker, and (a3) a hydrosilylation catalyst
Data Source
AI summary
A composition contains: (A) a curable silicone composition including: (a1) a vinyldimethylsiloxy-terminated polydimethylpolysiloxane having a viscosity in a range of 30-400 milliPascal*seconds, (a2) a silicon-hydride functional crosslinker, and (a3) a hydrosilylation catalyst, where the molar ratio of silicon-hydride functionality from the crosslinker to vinyl functionality is in a range of 0.5: 1 to 1: 1; (B) a filler treating agent comprising one or both of an alkyl trialkoxysilane and a mono-trialkoxysiloxy terminated dimethylpolysiloxane; and (C) a thermally conductive filler mixture including (c1) 40-55 wt%of aluminum nitride fillers, containing a blend of: (c1-a) 15-41 wt%of spherical aluminum nitride particles having a D50 particle size of 100 micrometers or more, and (c1-b) spherical or irregular shaped aluminum nitride particles having a D50 particle size of 20-80 micrometers; (c2) spherical aluminum oxide particles having a D50 particle size of 1-5 micrometers; and (c3) 10-20 wt%of irregular zinc oxide particles having a D50 particle size of 0.1-0.5 micrometer; where the total amount of the thermally conductive filler mixture is 94-97 wt%; and where wt%values are relative to the weight of the thermally conductive composition unless otherwise stated.