Polydimethylsiloxane (PDMS) has been widely used in various fields such as flexible electronics, wearable devices, chip thermal management, and biomedicine due to its excellent flexibility, chemical stability, biocompatibility, and processability. However, PDMS has extremely low intrinsic thermal conductivity, mainly derived from the disordered structure of its molecular chains and phonon scattering effects. This characteristic significantly limits its application in high-demand scenarios such as high-power electronic heat dissipation. Traditional enhancement methods usually rely on adding high thermal conductive fillers (such as ceramics, carbon materials, or metal particles) into the PDMS matrix to improve its thermal conductivity. However, these methods often face problems such as uneven filler dispersion, large interfacial thermal resistance, and difficulty in balancing electrical insulation and mechanical properties. Therefore, developing a preparation strategy for PDMS composites with both high thermal conductivity and functional integration has become an urgent technical demand in the field of thermal management.
To address the challenge of improving the thermal conductivity of polydimethylsiloxane (PDMS)-based composites, Dr. Xiang Yan from the Institute of Microelectronics of the Spanish National Research Council (CSIC) and the team of Marisol Martin-Gonzalez, Member of the European Academy of Sciences, reviewed this topic, proposed several innovative technical strategies, and discussed in depth its cutting-edge progress in electronic applications.
1. Optimization of Particle Interactions: Breaking Microscopic Thermal Resistance
In composites, phonon scattering at the interface between the matrix and fillers is the biggest obstacle to heat conduction. The article details the following optimization mechanisms:
Interface Engineering and Surface Modification
It discusses in detail the use of chemical methods such as silane coupling agents and surface grafting to enhance the affinity between fillers and PDMS segments, reduce interfacial gaps, and thereby lower interfacial thermal resistance.
"Synergistic Effect" of Hybrid Fillers
Fillers with a single dimension often struggle to balance packing density and network connectivity. The review points out that using 1D fillers (such as carbon nanotubes/fibers) to build long-range bridges, combined with 2D/0D fillers (such as BNNS/spherical alumina) to fill gaps, can construct a "bridge-island" structure, significantly improving phonon transmission efficiency.
Spatially Confined Forced Network Assembly (SCFNA)
This is a physical processing strategy with great industrial potential. By applying spatial confinement to the composite through a hot pressing process, filler particles are forced to contact closely, forming a high-density thermal conductive network, and achieving a performance leap at a low filling amount.
2. Construction of 3D Interconnected Networks: Building Continuous "Thermal Highways"
Compared with randomly dispersed fillers, a continuous three-dimensional skeleton can provide a lower thermal resistance path.
Template-Based Technology
The article focuses on the sucrose template method. Sucrose particles are used to build a sacrificial skeleton; after curing, sucrose is removed by water dissolution, leaving connected pores inside PDMS which are then backfilled with thermal conductive materials. This method is low-cost and environmentally friendly, and can effectively construct 3D interconnected networks.
Skeleton Growth and Impregnation
It discusses the strategy of growing or depositing thermal conductive nanoparticles (such as graphene, liquid metal) on prefabricated porous foams (such as polyurethane foam, melamine foam), followed by PDMS backfilling, achieving dual improvement of mechanical and thermal properties.
3. Oriented Alignment Technology: Overcoming the "Out-of-Plane" Heat Dissipation Pain Point
In chip packaging and thermal interface materials (TIMs) applications, thermal conductivity perpendicular to the film direction (Z-axis) is crucial, but this is often a weakness of layered materials. The review in-depth analyzes how to make fillers "stand up":
Ice Template Method
Using the repulsive force during ice crystal growth, nanosheets are squeezed into an ordered vertical array. The article compares isotropic, unidirectional, and bidirectional freezing technologies, pointing out that the bionic shell nacre structure can maximize vertical thermal conductivity.
Field-Assisted Alignment
Magnetic Field: Using magnetic nanoparticles to assist non-magnetic thermal conductive fillers (such as FeCo-BNNS) to achieve vertical alignment under the action of a magnetic field.
Electric Field: Using dielectrophoretic force to form chain-like structures of fillers along electric field lines, which can open up vertical thermal paths even at low filling amounts.
Force ield Control and Additive Manufacturing
It introduces cutting-edge technologies that use shear force at the nozzle of Direct Ink Writing (DIW) 3D printing or flow field shear in extrusion molding to induce high orientation of high aspect ratio fillers along the printing path.
4. Fiber and Fabric Integration: Macroscopic Enhancement
Not limited to nano-fillers, the article also discusses the use of macroscopic reinforcements such as ultra-high molecular weight polyethylene (UHMWPE) fibers and carbon fiber fabrics, which are integrated into PDMS through textile processes such as weaving and twisting, significantly improving the tear resistance of the material while enhancing thermal conductivity.
Beyond "Thermal" — The Future Form of Multifunctional Integration
A single thermal conductive function can no longer meet the needs of complex working conditions of modern electronic devices. This review specifically includes a chapter to discuss the "all-rounder" potential of PDMS composites:
High Insulation and High Voltage Resistance
Aiming at the problem that carbon-based fillers are prone to cause short circuits, the article analyzes the use of insulating ceramic fillers (BN, AlN) or core-shell structure design (such as insulating layer-coated carbon fibers) to achieve a balance between high thermal conductivity and high insulation.
Electromagnetic Interference (EMI) Shielding
Combining new fillers such as MXene and liquid metal, while solving heat dissipation, an efficient EMI shielding layer is constructed to protect precision circuits from interference.
Self-Healing and Flame Retardancy
Introducing dynamic covalent bonds (such as imine bonds) to endow the material with self-healing ability; using bionic structure design to improve flame retardant grade, ensuring the safety of equipment in extreme environments.
Thermal Energy Storage
Integrating phase change materials (PCM) to endow PDMS with "peak shaving and valley filling" thermal buffering capacity.
Sharpening the Tool — Simulation and Characterization Technology
To fundamentally understand the heat conduction mechanism, the review comprehensively compares current mainstream calculation and testing methods, providing methodological guidance for researchers.
Multi-Scale Computational Simulation
Molecular Dynamics (MD): Used to reveal atomic-scale interfacial thermal resistance and phonon transmission mechanisms.
Finite Element Analysis (FEA): Used to predict macroscale heat flow distribution of complex composite structures.
Machine Learning (ML): Assists in high-throughput screening of optimal filler formulations and structural designs.
Advanced Thermal Characterization
Laser Flash Analysis (LFA): The most commonly used non-contact measurement in industry, suitable for bulk materials.
Time-Domain Thermoreflectance (TDTR): Uses ultrafast lasers to detect thermal conductivity and interfacial thermal resistance of nanoscale thin films with extremely high precision.
Scanning Thermal Microscopy (SThM): Can intuitively image the thermal distribution of microscale regions with nanoscale resolution, which is a powerful tool for studying filler network connectivity.
Conclusion and Outlook
This review is not only a summary of existing technologies, but also points out the direction for future research. The author team points out that future research on PDMS thermal management materials will focus on the following three dimensions:
Scalability and Green Manufacturing: Develop low-energy consumption and environmentally friendly preparation processes, use recycled fillers to reduce costs, and promote the transformation of laboratory achievements to industrialization.
Breakthrough in Ultimate Interfacial Thermal Resistance: Approach the theoretical thermal conductivity limit of composites through more refined molecular design and nanoengineering.
Intelligent Response and Multifunctional Synergy: Develop intelligent thermal management materials that can respond to environmental changes (such as temperature, stress).
The research result, "Strategies for Enhancing Thermal Conductivity of PDMS in Electronic Applications", has been published in the journal Advanced Materials Technologies, providing valuable technical routes and research perspectives for researchers and engineers in related fields. With the continuous development of material science and technology, PDMS-based composites are expected to be increasingly applied in high-end fields such as electronic thermal management, flexible electronics, and intelligent wearable technology, becoming one of the key materials driving the development of a new generation of electronic devices and systems.
-
Written by
CoolingThermal Engineering TeamCoolingThermal is an automation equipment manufacturer based in Kunshan, China, specializing in heat pipe and vapor chamber production equipment since 2017. Our engineering team designs, builds, and commissions complete production lines covering forming, degassing, welding, testing, and assembly processes. The technical content on this blog is written by the same team that develops the equipment — based on real production experience, not secondary research.
