| Flexible electronics have characteristics of bendable and retractable shapes,and could work normally when subjected to large deformations,which could meet people's high requirements for the portability and flexibility of new generation electronic products.In recent years,flexible electronics have attracted much attention from researchers and have good application prospects in the fields of information,defense,energy,and medical treatment.As the basis of flexible electronics,flexible circuit boards could be summarized as an emerging technology of metal films coating on flexible plastic surface.After metallizing the flexible plastic surface,not only could the appearance of the metal be obtained,but many new properties could also be added,such as conductivity,corrosion resistance,electromagnetic interference shielding and so on.At present,the research hotspots on the metallization of plastic surfaces mainly focus on how to improve the adhesion between the substrate and the metal coating and the electrical properties of the metal coating.In this paper,polyethylene terephthalate(PET)was used as flexible plastic substrate to explore best spraying conditions and performances of Ag films.In addition,the adhesion between substrate and metal coatings were enhanced by chemical etching and molecular grafting method.Besides,highly conductive,reflective and adhesive silver-based composite films were prepared by three-component spray-spin-spray method.Finally,a complex flexible circuit was prepared by masking method to explore its application.The main results are as follows:(1)The substrate was treated by chemical etching and sensitization to produce many corrosion pits and improve interface wettability,which could provide conditions for adsorption and reduction of plated ions.Preparation silver films on the surface of modified substrate via two component spraying method.The relationship between mixture concentration and micrmorphology,appearance,deposition and optical constants of silver films were studied to obtain best conditions for spraying.The results of SEM showed that silver particles were evenly and densely distributed on substrate,and most of them were fine and round.Further study found that the thickness of cross section of silver films was about 350 nm,and it has a good conductivity,up to 7.07 ??·cm,which was 4.5 times that of bulk silver.In addition,Ag films shown a good flatness,and its surface roughness was only 17.8 nm.The average reflectance in the visible region and infrared spectral range were 93.31% and 99.45%,respectivity,which were much higher than the commercial Ag films.The films have excellent conductivity and optical properties.(2)PET substrate was modified by molecular grafting technology.The azide group in the TTA molecule was connected to the substrate and formed N-H bond under the action of ultraviolet light.Then TTD molecule formed Si-O-Si with TTA through the substitution reaction between the silane groups bond,which could achieve the purpose of the presence of thiol groups on the surface of the substrate.In addition,the silver layers were still tightly adhered to the surface of the substrate after cross-cut adhesion test,which showed significant effect of molecular grafting on the adhesion of composite films.Ag/GNS composite films were prepared by three component spray-spin-spray coating method.The results showed that the effective deposition amount of GNS increases with the increase of the doping amount of GNS.When doping amount was 5 g/L,the sheet resistance of composite films was 84 m?/sq,compared with silver films,the sheet resistance of composite films was reduced by about 60%.What's more,it could be found from the distribution of GNS that GNS filled the gap between silver particles and formed multiple conductive paths.Complex flexible patterns and simple flexible circuits were successfully prepared on the substrate surface by masking method.(3)On the basis of above research,Ag NPs@GNS composite nanomaterials were prepared by electroless plating to prevent GNS agglomeration.TEM showed that the diameter of silver nanoparticles on GNS was only 20 ? 50 nm.The results of 90o peeling test found that the peeling force between composite films and substrate was significantly increased from 1.2 N/cm to 4.8 N/cm by molecular grafting,and the actual adhesion of the composite films was greater than the peeling force.In addition,even if doped with composite nanoparticles,the composite films still maintained good flatness,average reflectance in the visible region and infrared spectrum were 89.96% and 99.02%,respectivity.Compared the Ag/GNS hybrid films,the sheet of Ag NPs@GNS/Ag composite films was reduced by 52.4%,and its was 80.3% for Ag films.This was because the silver nanoparticles on the surface of GNS could fill the gap between GNS and sprayed silver particles.The results of bending and neutral salt spray test showed that composite films have excellent bending resistance and corrosion resistance conductive stability.Combined with the masking method,a flexible circuit was prepared on the modified substrate surface and integrated electronic components,LED kept flashing alternately under the action of bending,indicating that this flexible circuit has certain application potential in the field of flexible electronics. |
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