In the 1960s, the Union Carbide Corporation developed the Parylene series polymer coating materials, due to excellent barrier properties, Parylene material has been widely used in moistureproof, mildewproof, anti-salt spray coating field. According to the different molecular structure, Parylene material is divided into Parylene N, C, D, HT and F types. This article will introduce Parylene F with high temperature resistance and anti-UV performance.

The structural features of Parylene F

In the Parylene family, Parylene N, C and D are chlorinated polymers, and fluorinated Parylene is a new generation of derivatives of the series of polymers, including benzene ring substitutions—Parylene F and methylene substituted—Parylene HT. With the improvement of the requirements for waterproof materials, the traditional Parylene N, C, D have been far from meeting the requirements of the market in high temperature and anti-UV functions, and the introduction of fluorine atoms can better improve the electrical properties, heat stability and anti-UV properties of the film. The preparation efficiency of Parylene HT is very low because of its production process limits, and Parylene F is relatively more commercial, and attracts more and more people's attention.

Film forming principle of Parylene F

Similar to other Parylene materials, the preparation of Parylene F films is carried out on special vacuum coating equipment. The equipment consists mainly of sublimation furnaces, cracking furnaces, deposition chambers, cold traps and vacuum systems. The film formation process also includes the following three steps:

(3) After the monomer radical enters the deposition chamber, the polymerization is carried out on the surface of the substrate to form Parylene F film consistent with the shape of the object.

Preparation of Parylene F Films

Parylene F films were prepared by vacuum chemical vapor deposition using PDS2010 coating furnace and quartz glass plate as matrix by ZHAO Zongfeng et al. [1]. In the preparation process, the substrate temperature, substrate surface state, sublimation temperature, cracking temperature, deposition chamber pressure and other factors have a certain impact on the film performance and quality: if the high impurity gas content in the deposition chamber background pressure is high, free radicals are easy to lose activity to form short-chain polymer accumulation; high sublimation temperature will increase the pressure difference when gas into the deposition chamber, making the film deposition rate too fast and film quality is poor; cracking temperature will also affect the film quality.

Finally, the maximum sublimation temperature is 170℃, the cracking temperature is 690℃, the vacuum of the deposition chamber is 10mT, and the deposition pressure is 32mT. The resulting Parylene F coating is continuous, uniform, dense, has high dielectric strength and low dielectric constant and is excellent in thermal stability and can be used as a protective film for various complex shapes of electronic devices. And vacuum chemical vapor deposition process does not use solvents, will not produce environmental pollution.

In high temperature and anti-ultraviolet, Parylene F has a strong advantage, which makes up for the defects of traditional Parylene material. In addition, Parylene F also has the waterproof and electrical insulation and other excellent performance of traditional Parylene material, which can be applied to medical equipment, cars, motor switches, wearable equipment and high value-added LED.

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