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Thermal management is a major challenge in electronics. Heat dissipation performance directly affects operational stability and reliability; about 55% of electronic failures are caused by excessive temperature.
With the arrival of 5G and rapid advances in information technology, artificial intelligence, and the Internet of Things, functions integrated into a single electronic device have increased and become more complex. Shrinking device sizes raise power density rapidly, placing higher demands on the thermal performance and stability of heat dissipation materials.
01 Graphite Film Overview
Traditional metal materials such as copper and silver have high thermal conductivity, but they are dense, have limited formability, oxidize at high temperature, and are relatively expensive. Carbon-based materials, such as carbon fiber, carbon foam, and graphite film, provide competitive thermal conductivity and are therefore attractive for cooling microscale electronics.
Graphite film has excellent electrical and thermal conductivity and is lightweight and thin. Compared with traditional metals, graphite film can offer higher thermal conduction with lower density. Since 2011, graphite film has been widely used in smartphones, tablet computers, and other consumer electronics, becoming a mainstream heat dissipation material.
The carbon atom arrangement in high-thermal-conductivity graphite film features a distinct grain orientation that enables uniform heat conduction along two dimensions, resulting in excellent in-plane thermal performance.
In theory, thinner graphite film yields higher thermal conductivity. Early graphite films were typically 20–50 μm thick, with in-plane thermal conductivity between 300 and 1,500 W/(m·K). With process improvements, graphite film manufacturing has matured; the thinnest commercially available is now about 0.01 mm, with in-plane thermal conductivity reaching up to 1,900 W/(m·K).
02 Graphite Film Types
Graphite film types mainly include natural graphite film, nano-carbon thermal film, and artificial graphite film. Natural graphite film is made entirely from natural graphite. It does not off-gas under vacuum, can be used at temperatures above 400°C, and can be produced down to about 0.1 mm thickness. Typical applications include data centers, base stations, and charging stations.
Artificial graphite thermal film is produced by carbonizing and graphitizing polyimide (PI) film. It is currently the thinnest thermal film material, down to 0.01 mm, and is widely used in smartphones, computers, and other smart terminals. Artificial graphite is more widely used because its thermal conductivity and achievable thickness outperform natural graphite.
Nano-carbon thermal film is made from nano-carbon (a graphite allotrope). The thinnest can reach 0.03 mm, and thermal conductivity can be as high as 1,000–6,000 W/(m·K). Nano-carbon film processing is simple, requiring only die-cutting, which keeps processing costs low; however, nano-carbon itself is very expensive and yields are low.
03 Production Processes for Graphite Film
Preparation processes differ significantly between natural and artificial graphite film. Natural graphite film is manufactured from natural graphite through acid treatment, expansion, calendering, carbonization, and graphitization.
Natural graphite film production process
Artificial graphite film is produced from polyimide (PI) film via carbonization and graphitization. From a production standpoint, it typically involves six main steps: substrate treatment, carbonization, graphitization, calendering, lamination, and die-cutting.
Artificial graphite film production flow
Carbonization is conducted under vacuum or inert gas at approximately 1000°C to remove most oxygen, nitrogen, and hydrogen from the film, producing a stable carbon film. Graphitization then heats the carbonized film to around 3000°C under inert gas to form graphite. Graphite films produced by this method have thermal conductivity in the range of 1000–1800 W/(m·K).
04 Artificial Graphite Film Industry Chain
The artificial graphite film industry chain includes upstream polyimide (PI) film, midstream graphite film, and downstream applications. Upstream raw materials are mainly polyimide (PI) film, with ancillary materials such as adhesive tapes and protective films.
05 Thermal-Grade Polyimide
Among carbon materials, graphene has a hexagonal ring structure. A large-area, regular hexagonal structure favors both electrical and thermal conductivity, so graphene has the highest thermal conductivity, up to 5300 W/(m·K). Among polymer precursors, polyimide contains many benzene rings and imide rings, structures similar to graphene, which helps improve the thermal performance of finished graphite film. For this reason, polyimide film is used as the precursor for artificial graphite thermal films.
Thermal-grade polyimide film is a high-performance PI material with high technical barriers. In China, Ruihuatai and Shidai Huaxin have achieved large-scale production. Public data show that the Chinese thermal interface materials market expanded from 660 million yuan in 2014 to 1.27 billion yuan in 2020. In recent years, the Chinese graphite film market experienced some decline due to weak downstream demand. Ruihuatai reported that a contraction in global consumer electronics markets, product mix changes, and lower selling prices led to reduced gross margins. The thermal-grade PI film market is also competitive, and since early 2023 the Korean company PIAM has substantially reduced thermal-grade PI film prices.
Despite the recent downturn in the thermal-grade PI film market, 5G-driven increases in device power consumption and the rise of foldable phones support continued demand for high-thermal-conductivity graphite films derived from thermal-grade PI film.
Public data indicate the global thermal interface materials market reached 1.711 billion USD in 2022, with a 2015–2022 CAGR of 12%. It is estimated that by 2025 the unit price of graphite for 5G phones will be 8.9 yuan, and the global graphite-for-phone market will reach about 16.3 billion yuan.
As device power increases and fast-charging technologies demand higher thermal performance, graphite films will evolve from traditional single-layer films to composite graphite films while applications for thicker graphite films will increase. At the same time, the growing penetration of foldable smart devices and rising AMOLED demand are driving demand for artificial graphite thermal films. Foldable AMOLED requires foldable-compatible thermal films with good bend resistance. Developing thermal-grade PI precursors that combine high thermal conductivity with high flexibility will be a key direction.
