Classification and Preparation Processes of High-Thermal-Conductivity Graphite Films
In the field of electronic device thermal management, high thermal conductivity graphite films can be categorized into three main types based on material origin and preparation process: natural graphite thermal films, artificial graphite thermal films, and graphene thermal films. These materials exhibit distinct characteristics in thermal conductivity, thickness range, and production costs, offering diverse solutions for different application scenarios.
Natural graphite thermal films utilize natural flake graphite as raw material, typically maintaining a carbon content above 97%. Research data indicates a positive correlation between raw material carbon content and the final product's graphitization degree and thermal conductivity. Consequently, the industry prioritizes high-purity natural graphite with carbon content exceeding 99%. Raw material particle size is typically controlled within the 20-80 mesh range. Excessively small particles result in insufficient graphite diameter after expansion, compromising sheet rolling quality. Conversely, overly large particles reduce product strength and destabilize crystal structure integrity.
Currently, commercially available natural graphite thermal interface materials predominantly utilize the expandable graphite (EG) process route. The complete production process encompasses raw material screening, screw conveying, high-temperature expansion, cooling and separation, pre-press forming, matting treatment, trimming, and winding. Benefiting from a mature process system, domestic natural graphite thermal interface materials enjoy significant cost advantages. However, their horizontal thermal conductivity is limited to the 200–400 W/(m·K) range, with typical product thicknesses of 0.05–0.3 mm, presenting performance bottlenecks in high-end thermal management applications.
Artificial graphite thermal films utilize polyimide (PI) film as their core material. This material is synthesized through polycondensation of terephthalic anhydride and diaminodiphenyl ether in a highly polar solvent, followed by casting and imidization processes. It is important to note that while PI films are widely used in consumer electronics, not all grades are suitable for high-thermal-conductivity graphite film production. Only high-quality PI films with specific properties meet the requirements.
The core technology of this product lies in two critical stages: carbonization and graphitization. Carbonization occurs under nitrogen protection or vacuum conditions at temperatures ranging from 800 to 1500°C, requiring appropriate pressure to prevent film wrinkling. Graphitization is performed under inert gas protection (argon or helium) at temperatures reaching 1800 to 3000°C. The high-temperature-treated PI film forms a highly thermally conductive graphite film substrate, which undergoes subsequent processing such as calendering, lamination, and die-cutting before being integrated into electronic devices.
Compared to natural graphite processes, the production of artificial graphite thermal interface materials involves a more complex workflow and significantly higher raw material costs. However, it achieves major performance breakthroughs, with horizontal thermal conductivity reaching 1200–2000 W/(m·K) and product thickness controlled within 0.025–0.06 mm. Recent technological advancements reveal that the industry has successfully developed high-performance products with thermal conductivity reaching 2200 W/(m·K), marking a new pinnacle in material performance.
Leading international players in this field include Panasonic, Kaneka, and U.S.-based Graftech. Domestic manufacturers such as Zhongshi Technology, Siquan New Materials, Feirongda, and Carbon Yuan Technology have also established comprehensive industrial chains.
Graphene thermal films represent a fundamental breakthrough in manufacturing processes. Starting with graphene oxide, the technology involves dissociation and dispersion followed by additive incorporation to create a uniform dispersion. This is then processed through stirring and degassing, coating and forming, and drying to produce the base film material. These semi-finished products undergo dual high-temperature carbonization and graphitization treatments to form the graphene thermal film prototype, with final product manufacturing achieved through calendering and die-cutting processes.
Although the production cost of graphene thermal films is significantly higher than the previous two types of products, their theoretical thermal conductivity achieves a leapfrog improvement, with a horizontal thermal conductivity coefficient reaching 1000-5000 W/(m·K). Currently, commercially available products generally maintain a range of 1200-2000 W/(m·K), comparable to artificial graphite films. However, graphene films offer a distinct thickness advantage, ranging from 0.1 to 0.3 mm, providing greater design flexibility for thermal management solutions.
Application Positioning and Technology Evolution Path
In the field of consumer electronics thermal management, graphite thermal films have become a mature solution widely adopted in products such as smartphones, laptops, and wearable devices. It should be clarified that graphite thermal films do not strictly fall under the category of thermal interface materials. The core function of such materials lies in their heat spreading capability across a planar surface. By rapidly dispersing energy from point heat sources evenly across the entire plane, they effectively prevent device failures caused by localized heat buildup.
From a technological evolution perspective, natural graphite thermal sheets represent the first-generation technology. Leveraging mature manufacturing processes and cost advantages, they were widely adopted in scenarios with modest thermal management requirements. However, as the power density of electronic components continues to increase, their thermal performance has become insufficient to meet the demands of high-end devices.
Artificial graphite thermal films, as second-generation technology, exhibit exceptional thermal conductivity. Notably, their thickness inversely correlates with thermal performance—increased thickness reduces thermal conductivity. While ultra-thin designs enhance thermal efficiency, practical applications must also account for heat flux considerations. Appropriately increasing material thickness enhances thermal buffering capacity, enabling steady heat dissipation—a critical feature in mobile device design.
Graphene thermal films, regarded as third-generation technology, not only surpass the thermal limits of artificial graphite films (with a theoretical thermal conductivity of 5300 W/(m·K) for single-layer graphene) but also achieve significant breakthroughs in thickness design and thermal flux performance. Current mainstream products range from 0.1 to 0.3 mm in thickness, with the 0.2 mm specification enjoying the highest market acceptance due to its optimal balance between thermal performance and thermal management requirements.
Market Competitive Landscape and Development Trends
In terms of market structure, natural graphite thermal interface materials, characterized by low technical barriers and significant cost advantages, primarily dominate the low-end product segment. Their market share remains relatively stable with few new entrants.
Artificial graphite thermal films currently dominate the market, with their cost-performance advantages becoming increasingly prominent. Taking the 1200W/(m·K) specification as an example, market prices have dropped to 40-50 RMB per square meter, representing a three- to five-fold decrease compared to a decade ago. This transformation is primarily driven by breakthroughs in domestic PI film material technology. Companies like Zhuzhou Times and Ruihuatao have successfully broken foreign technological monopolies, optimizing the cost structure of the industrial chain. Major domestic manufacturers now widely utilize domestically produced high-performance PI film raw materials.
Graphene thermal films are currently in the market cultivation phase. While theoretically possessing the potential to replace artificial graphite films, their cost-performance advantage remains underutilized due to constraints in process complexity and yield rates (industry-leading levels still below 80%, compared to over 95% for artificial graphite films). The industry is exploring new application directions, including composite solutions with artificial graphite films and innovative pathways such as using graphene as raw material for thermal pads. Recent orders from manufacturers like Huawei have injected new momentum into industry development.
Industry projections indicate the global graphite thermal film market will reach $1.189 billion by 2025, with a compound annual growth rate (CAGR) of 2.58% from 2025 to 2032. Growth will primarily stem from upgraded thermal management demands in smartphones and new energy vehicles. Apple, a key industry bellwether, continues to adopt synthetic graphite thermal film solutions while offering favorable terms to suppliers, underscoring the market position of this mainstream technology.
Overall, the technological evolution from natural graphite to artificial graphite and then to graphene clearly illustrates the trajectory of escalating thermal management demands in consumer electronics. Although graphite thermal films represent only a niche segment within thermal management, their innovation and industrial upgrading pathways fully demonstrate the foundational role of materials science in advancing electronic product development.
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