Adhesion property of novel polyimides with 1‐[3′,5′‐bis(trifluoromethyl)phenyl] pyromellitic dianhydride

Abstract

Novel polyimides were synthesized from 1-[3Ј,5Ј-bis(trifluoromethyl)phenyl] pyromellitic dianhydride (6FPPMDA) by a conventional two-step process: the preparation of poly(amic acid) followed by solution imidization via refluxing in p-chlorophenol. The diamines used for polyimide synthesis included bis(3-aminophenyl)-3,5-bis(trifluoromethyl)phenyl phosphine oxide, bis(3-aminophenyl)-4-trifluoromethylphenyl phosphine oxide, and bis(3-aminophenyl)phenyl phosphine oxide. The synthesized polyimides were designed to have a molecular weight of 20,000 g/mol by off-stoichiometry and were characterized by Fourier transform infrared, NMR, differential scanning calorimetry, and thermogravimetric analysis. In addition, their intrinsic viscosity, solubility, water absorption, and coefficient of thermal expansion (CTE) were also measured. The adhesion properties of the polyimides were evaluated via a T-peel test with bare and silane/Cr-coated Cu foils, and the failure surfaces were investigated with scanning electron microscopy. The 6FPPMDA-based polyimides exhibited high glass-transition temperatures (280 -299°C), good thermal stability (Ͼ530°C in air), low water absorption (1.46 -2.16 wt %), and fairly low CTEs (32-40 ppm/°C), in addition to good adhesion properties (83-88 g/mm) with silane/Cr-coated Cu foils.

Synthesis and property measurements of polyimides with substituted pyromellitic dianhydride for flexible printed circuits applications

“…Compared with the previous study, which reported peel strength of 94 and 91 g/mm with PPMDAmDAPPO and 3FPPMDA-mDAPPO polyimides, 19 much higher peel strength was observed in this study (130 and 121 g/mm). This difference can be explained by the different sample geometry: Cu/polyimide samples in this study compared to the Cu/polyimide/Cu samples in the previous study.…”

“…19 The Cu/polyimide samples were prepared by brush coating the polyimide solution (15 wt % in NMP) on Cu foil and drying at $ 100 C for 15 min. The process was repeated until the coating thickness reached 0.04 mm, because the polyimide layer has to be thick enough to minimize plastic deformation during testing.…”

“…In addition, structural modification of polyimides by incorporating imidazole, 14 pyridine, 15 or phosphine oxide groups 16,17 has also been attempted to enhance the adhesive property.and diamine monomers with adhesion promoting functional groups via solution imidization, but they provided slightly inferior properties for FPC applications. 18,19 In this study, therefore, it was attempted to prepare polyimides from pyromellitic dianhydride (PMDA)-based dianhydrides, a diamine with phosphine oxide moiety and 4,4 0 -phenylene diamine (pPDA). The polyimides were synthesized via a conventional two-step synthesis; preparation of poly (amic-acid), followed by solution imidization.…”

Synthesis and characterization of polyimides from 4‐(diphenyl phosphine oxide)phenyl pyrromellitic dianhydride

“…In comparison, the ASTM D-1876 T-peel test samples (Cu/polyimide/Cu) of PPMDA-mDAPPO polyimide showed cohesive failure, despite their lower peel strength, as previously reported. 34 This can be explained by the poor flow of polyimide adhesives during thermal lamination due to their high T g , which resulted in failure occurring at the interface of two polyimide layers, despite the misleading appearance of cohesive failure.…”

“…34 The modified T-peel test samples were prepared by brush coating the Cu foil with polyimide solution (15 wt % ) from the benzene ring, indicating a successful synthesis.…”