Preparation Of Thermoplastic Polyimide Flexible Copper Clad Laminate

Polyimide(PI) is one of the high-performance polymer materials, which contains imide cycles in the mainchain of the molecule, possessing excellent mechanical properties, insulation, irradiation resistance, corrosion resistance, high or low temperature resistance. Polyimide has been widely used in many special fileds, such as fire protection, electronics, aircraft and aerospace industries and military fileds. It also has drawbacks, such as too high melting point at which the polymer is difficult to process, easier hydrolysis, weaker adhesion and higher cost etc. Recently, the research for the synthesis, modification and application of thermoplastic polyimides has got much more attention.A series of BPDA-BTDA-p-PDA-ODA copolyamide acids with different composition were prepared in this paper. Polyimide film and two layer PI flexible copper clad laminate(2L-FCCL) were obtained via the conventional two-step thermal process. In order to enhance the properties of the PI film and FCCL, they were modified by adding mica and PMDA. The mechanical property, morphology, thermal property, dimentionally-stable property and peel strength of PI film and PI/Cu composite material were characterized by Fourier transform infrared spectroscopy(FTIR), thermogravimetric(TG), differential scanning calorimetry(DSC), scanning electron microscop(SEM), thermal mechanical analyzer(TMA), universal testing machine and the test of weld temperature resistance etc.The resulting BPDA-BTDA-p-PDA-ODA copolyimide had good thermal stability, with initial decomposition temperature of higher than 520℃, glass transition temperature of lower than 250℃, tensile strength of 160.62MPa, peer strength of 1.220kgf/cm and passed the test of 320℃boiled stannum. With the incorpaoration of PMDA in the main molecule chain, the solubility of the copolyimde in common organic solvents, the dimentionally-stable property and peel strength of PI film and 2L-FCCL could be improved. When the mole content of PMDA in the dianhydride was 20%, the property of the product reached the best. By the modification of mica, the dimentionally-stable property, peel strength and weld temperature resistance of PI film and 2L-FCCL have been greatly improved. The coefficient of thermal expansion (CTE) of modified film was decreased(1.831×10-5/℃), which was similar to the CTE of copper film(1.6×10-5～1.8×10-5/℃). This modified film has high application value.