Preparation and properties of heat-sealable polyimide films with comparable coefficient of thermal expansion and good adhesion to copper matrix

Abstract

Abstract.A series of thermoplastic polyimide (PI) films (PI-1~PI-5) with intrinsic heat sealability have been synthesized by the high-temperature polycondensation reaction of asymmetrical 2,3,3ꞌ,4ꞌ-oxydiphthalic anhydride (aODPA) and various aromatic diamines in order to meet the demands of advanced flexible copper clad laminates (FCCL). The derived PI resins had good solubility in polar aprotic solvents, such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) at a solid content up to 20 wt%. Flexible and tough films could be cast from the PI/NMP solution and the films exhibited tensile strength higher than 83 MPa. Among the developed PIs, those derived from aODPA and benzimidazole-containing diamines, including PI-4 from aODPA and 2-(4-aminophenyl)-5-aminobenzimidazole (4APBI) and PI-5 from aODPA and 2-(3-aminophenyl)-5-aminobenzimidazole (3APBI) exhibited the highest thermal stability (glass transition temperatures, T g > 340°C), lowest linear coefficients of thermal expansion (CTE < 35·10 -6 1/K), and superior adhesion to copper foil (peeling strength >1.0 N/mm). Flexible copper clad laminate (FCCL) with no curling was successfully prepared from PI-4 and copper foil.

Synthesis of Superheat-Resistant Polyimides with High Tg and Low Coefficient of Thermal Expansion by Introduction of Strong Intermolecular Interaction

“…The TGA curves of these PIs are illustrated in Figure S8. All PIs showed a similar decomposition behavior in nitrogen that was characterized by a 5% weight loss from 553 to 579 °C, which showed a more attractive thermal stability than previous reported PIs. − Polyimides with a rigid chain possess a higher thermal stability compared with PIs that have flexible, hinged bonds in their chains . The PI-a and PI-b contained unbroken conjugated rigid chains, i.e., no hinged heteroatoms in the main chains.…”

Symmetrical “Sandwich” Polybutadiene Film with High-Frequency Low Dielectric Constants, Ultralow Dielectric Loss, and High Adhesive Strength

“…The excellent dielectric materials not only had exceptional adhesion but also had a very low dielectric constant and dielectric loss. , However, strong adhesion and excellent dielectric properties of polymer materials were often contradictory. On one hand, strong adhesion requires that polymer chains contained polar functional groups such as aminos, cycloxyls, and isocyanates, which can enhance the interfacial forces between polymer chains and microstrip conductors by electrostatic interaction, thereby improving the durability and reliability of integrated circuit boards.…”

Synthesis of quaternary copolymerized fluorine-containing polyimides with good thermal properties and low dielectric constant

“…From the DMA diagram of PI-1∼PI-5, the storage modulus of these five PI films decreases sharply around their T g and the dropped amplitudes are above 10 3 MPa/°C, showing good thermoplastic. 12,32 This good thermoplastic is originated undoubtedly from the high free volume and weak chain interaction caused by the distorted structure in α-BPDA. In addition, the introduction of ether bond and trifluoromethyl in HFBAPP increases the distance in the molecular chain, which is another reason for the decrease of PI' storage modulus near T g .…”