Production process of high thermal conductivity graphite sheet

High thermal conductivity graphite sheet is a new heat dissipation material developed in recent years by using the excellent thermal conductivity of graphite. The product is a sheet material with high thermal conductivity made by repeated heat treatment of polymer film based on carbon material under special sintering conditions. It has the characteristics of thin thickness, high heat dissipation efficiency and light weight.

When consumer electronics are faced with problems such as local overheating, rapid heat conduction, and space limitations, the high thermal conductivity graphite sheet provides a good heat dissipation solution. Therefore, in recent years, the high thermal conductivity graphite sheet has been applied in the field of consumer electronics such as smart phones, ultra-thin laptops, tablet computers, LED and TV, etc.

The following describes the production process of Dasen’s high thermal conductivity graphite sheet. The production process mainly includes six processes such as substrate treatment, carbonization, graphitization, calendering, laminating and die-cutting.

1. Carbonization and graphitization

Carbonization and graphitization are the core processes in the above process, which Dasen uses professional treatment of PI films in customized carbonization furnaces and graphite furnaces to obtain large graphite primary films.

Carbonization is the pre-graphitization procedure, which aims to make all or most of the non-carbon components in the PI film volatilize, and needs to be carried out at a specific high temperature. By adding inert gases such as argon or nitrogen into a special carbonization furnace, and controlling the heating rate and carbonization temperature, the radial arrangement of PI membrane molecules is disrupted, the carbonyl group is fractured, and the aromatic heterocyclic polycyclic compounds are formed after chemical changes.

In the graphite chemical process, we further heated the carbonized PI film by adding argon or nitrogen as the medium in a special graphitization furnace, and reformed the polycyclic compound molecules at high temperature. With the oscillating operation of several periodic temperature rises, a large area of graphite original film with high crystallity was finally formed through chemical changes. By setting different temperatures and different temperature control methods, we can produce high thermal conductivity primary films with different parameters.

In the above process, the selection of raw materials, the manufacture of carbonization and graphitization furnace, the selection of heating rate, the control of carbonization and graphitization temperature, the control mode of heating and cooling in graphitization, the formulation of reference temperature and threshold value, and the regulation of periodic oscillation all affect the quality of the high thermal conductive graphite primary film and even the success of preparation.

2. Calendering and Laminating

After the two processes of carbonization and graphitization are completed, it is also necessary to calender and laminate for the final die cutting link.

Due to the existence of bubble domains, the density and thermal conductivity of the graphite film are low in the production process. In order to obtain high density graphite film and improve its thermal conductivity, it is necessary to calendering treatment. Dasen passes the graphite primary film through a series of horizontal roll gaps rotating opposite each other in a controlled manner, allowing the material to be squeezed and extended, resulting in a sheet product. In this process, the design of the processing equipment, the rate of rotation and the selection of the horizontal roll gap all affect the thickness, width and surface finish of the rolled product, which requires a high level of technology.

The graphite film of the sheet product still needs to be closed for protection before it can be used in the product, so the surface of the graphite film needs to be laminated. In the laminating process, we need to use a specific machine to combine the graphite film with the acrylic tape through a series of horizontal roll gaps rotating opposite each other, and attach the release film and the protective film. In this process, we are processed according to special equipment and control requirements, so that the coating layer is uniform and the thickness is as small as possible to ensure the quality of subsequent products.

3. Die cutting

In the die cutting process, Dasen uses specific machines to cut the calendered high thermal conductivity graphite film into different shapes and sizes through precision machining and cutting according to customer requirements. With the development of smart phones to ultra-thin, the space reserved for heat dissipation materials is increasingly limited, which puts forward more diversified applicability requirements for the shape and size of the high-thermal graphite film, so the die-cutting equipment and the fine operation of the cutting process play a crucial role in the final product.

Dasen can provide custom high thermal conductivity graphite roll and die cut parts according to different requirements of customers, welcome to contact us!