A large number of structural studies, is now concluded. Polyimide film should be used for rigid rod-like molecular structure. For example PMDA / ODA, BPDA / PPD, BPDA / ODA and these copolymers monomers. Mumata, who studied the various structures of the polyimide film CTE values of a free state and imidization of the resulting thin film metal frame under way fixed case. The PMDA / 2,5-DAT obtained polyimide has a CTE of 4 × 10-7 / ℃, quartz glass considerably.
In the case of two-way fixed imidization resulting film than in the free state, the resulting film has imidization farmland CTE. Any diamine a single aromatic ring, two amino each other to bits when you can get a low CTE. Seen from the molecular chain conformation, these macromolecular conformation is not curved. Those who bent conformation with polyimide have high CTE. Because the thermal expansion of the free volume expansion is generally considered to steric hindrance macromolecules with small rigid-rod structure. It can make a tighter molecular chains have a pile of free volume is small, and therefore should have a lower CTE. But in checking the CTE and found a pile of free volume coefficient is not the main factor affecting the CTE. Because they have high free volume polymer may be composed of a low CTE, having a low free volume of the polymer may also have a high CTE.