Polyimide is one of the organic polymer materials with the best comprehensive properties. Its high temperature resistance is above 400℃, long-term use temperature range -200 ~ 300℃, no obvious melting point, high insulation performance, 103-h dielectric constant 4.0, dielectric loss is only 0.004 ~ 0.007, belongs to F to H.

According to the chemical structure of repeating units, polyimides can be classified into aliphatic, semi-aromatic and aromatic polyimides. According to the interaction forces between chains, they can be divided into crosslinked and non-crosslinked types [1].

Polyimide is a kind of polymer containing imide ring (-co-n-co -) on the main chain, among which polymer containing phthalimide structure is the most important. As a special engineering material, polyimide has been widely used in aviation, aerospace, microelectronics, nanometer, liquid crystal, separation film, laser and other fields. In the 1960s, the research, development and utilization of polyimide were listed as one of the most promising engineering plastics in the 21st century.

Polyimide, because of its outstanding characteristics in performance and synthesis, whether as a structural material or as a functional material, its huge application prospects have been fully recognized, known as "protion solver", and that "without polyimide there would not be today's microelectronics technology".