Preparation And Properties Of Thermoplastic Polyimide Films Used For 2L-FCCL

Polyimide is widely used in flexible copper clad laminte because of its excellect mechanical properties,thermal stability,insulation,low dielectric property and so on.With thermoplastic polyimide(TPI)instead of intermediate adhesive layer such as epoxy and acrylic resin,the two-layer flexible copper clad laminate(2L-FCCL)has so many advantages of light weigt and better thermal stability.It is widely applied in the field of microelectronics,aerospace and other fields,and is a new direction of future development.At present,two-side 2L-FCCL occupys the market share of 80%while the lamination method is the only production process that can produce two-side 2L-FCCL on a large scale.However,there are many problems such as high processing temperature and low peeling strength.The purpose of this paper is to research the thermoplastic polyimide film which can be used to produce 2L-FCCL at low temperature.Polyimide BPDA-ODA which was synthesized with 3,3',4,4'-Biphenyltetracarboxylic dianhydride(BPDA)and 4,4'-Oxydianiline(ODA)was selected as basement film with high-dimensional stability.3,3',4,4'-benzophenonetetracarboxylic dianhydride(BTDA),4,4'-Oxydianiline(ODA)and 2,2-Bis[4-(4-aminophenoxy)phenyl]propane(BAPP)were selected to get six kinds of polyamide acids(PAA)which were coated on glass plate and basement membrane by coating method,and then TPIs and composite polyimide films were obtained by solvent removal and thermal imidization.Combined with copper foil,2L-FCCLs were gotten by laminating method.Selecting peeling strength as the main reference performance,the TPI BTDA-ODA-BAPP with the best comprehensive performance was screened out.The aim was to improve the peeling strength to meet the industry standard of 2L-FCCL(?0.7N/mm)by adjusting the molar ratio of ODA,BAPP and adding silane coupling agent(KH-550);Solve the problem of esay separation between TPI and basement film by surface treatment of the basement film;The thermal properties of TPI films were further characterized by thermal degradation kinetics.The activation energy(Ea)was calculated by Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods,and the mechanism of thermal degradation reaction was analyzed by Coats-Redfem method.The structure,thermal stability,dielectric and mechanical properties of TPI films,the peeling strength and morphology of peeling surface of 2L-FCCL were studied by Fourier transform infrared spectrometer(FTIR),thermogravimetric(TG),impedance analyzer,tensile testing machine,scanning electron microscope(SEM)etc.The results showed that the use of monomers,the addition of silane coupling agents and the surface treatment on base film all had important effects on the properties of polyimide film and the corresponding 2L-FCCL.The peeling strength of 2L-FCCL which was prepared by TPI BTDA-40%ODA-60%BAPP modified with 3%mass fraction of KH-550 was the largest,which reached 0.84N/mm and met the requirements of FCCL industry.The tensile strength of this TPI film was up to 101.34MPa and T5%reached 517.82?.These all showed excellent mechanical properties and thermal stability of the TPI film.After 20min of surface treatment of acid and alkali on basement film,the phenomenon of separation between TPI and basement film did not appeared.TG-DTG analysis showed that the degradation of TPI BTDA-40%ODA-60%BAPP was a two-step reaction process.The activation energies of two steps of TPI BTDA-40%ODA-60%BAPP were 187.62 kJ/mol and 214.54 kJ/mol by Flynn-Wall-Ozawa method,respectively,and were 184.10 kJ/mol,211.45 kJ/mol by Kissinger-Akahira-Sunose method.The thermal degradation reaction mechanism of first step of TPI BTDA-40%ODA-60%BAPP was F1,and the reaction mechanism of second step was D1.