Synthesis of silane-modified polyimide enamel for thermally stable electrical insulation coatings

The polyimide resin, recognized as a high-performance polymer, owes its distinction to remarkable heat resistance, positioning it as a versatile material with widespread applications across various sectors. Polyimide dielectric films are very important in modern electronics industries and power systems at high temperatures, but their poor adhesion to copper limits their application. Plain polyimide enamel of benzophenone tetracarboxylic dianhydride (BTDA) and diamino diphenyl sulfone (DDS) lacks adhesion and flexibility on copper due to its rigid structure. In this work silane terminated polyimide enamel was synthesized by reacting anhydride end polyamic acid obtained from BTDA and DDS with amino propyl tri methoxy silane (APTMS) in N-methyl pyrrolidone (NMP). Silane content was varied to achieve excellent adhesion on copper. Further, DDS was partially replaced with polyether amine, Jeffamine D400, to enhance flexibility of the coatings. Optimized enamels were characterized by viscosity, Fourier transform infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy, thermogravimetric analysis (TGA), Dielectric properties such as breakdown voltage, volume surface resistivity, dielectric constant, tan delta, etc. Mechanical properties such as adhesion, impact resistance, hardness, and chemical properties such as acid and alkali resistance, hydrolytic stability, solvent rub test, and water absorption.