Research On Technology Of Surface Modification And Metallization On Polyimide Substrate

Flexible electronics have received extensive attention in the fields of communication,medical care,and national defense security due to their good flexibility,ductility and diversity of structural functions.Polyimide has become one of the most important substrates in the field of flexible electronics due to its good dielectric properties,heat resistance and stability of physicochemical properties.However,PI film has poor polarity and the surface is usually very smooth,making it difficult to form an effective bond with the metallic functional layer.These drawbacks greatly hinders its application and development in the field of flexible electronics.Therefore,the surface modification and metallization technology of PI film has become the focus of research in this field.Based on the analysis of the surface physicochemical properties and modification technology of PI substrate,metallized PI is prepared by surface modification and electroless plating.The main research contents are as follows:(1)Analyze the surface modification methods commonly used in PI substrate.By analyzing and characterizing the surface physicochemical properties of the modified PI substrate and the quality of the copper layer after metallization,the surface modification method suitable for the PI substrate is determined as follows.First,a hydrolysis layer is formed on the surface of PI substrate by chemical etching,then functional groups which could chemically bonded with the metal layer are introduced on the surface of the PI substrate using a grafting modifier.The optimal scheme for PI substrate modification is determined by FTIR spectrum and contact angles with water of PI substrate before and after modification: The PI film is modified with a 100g/L aqueous solution of KOH at a bath temperature of 50 ° C for 30 min;The hydrolyzed PI substrate is graft modified with a branched PEI aqueous solution at a water bath temperature of 70 ° C for 90 min.The physical properties and chemical properties of PI substrates before and after modification are analyzed by SEM,AFM,EDS,FTIR and contact angles with water.(2)A metallic copper layer is prepared on the surface of the modified PI substrate by chemical liquid deposition.The surface morphology,crystallinity,adhesion and electrical conductivity of the copper layer are investigated.The above research results show that the branched PEI crosslinked with glutaraldehyde is used as a modifier to act on the PI film after alkali treatment,and a special morphology is obtained on the surface of PI substrate.This PEI-modified PI film possesses not only functional groups for chemical bonding but also large surface roughness(63.4 nm)for mechanical locking with metallic copper layer.After electroless plating,the copper layer on the surface of PI substrate has good electrical.The resistivity is about ???cm,which is only 1.37 times of the bulk copper.The adhesion of the copper layer on the surface of PI substrate meets the ASTM Class 5B standard.Metallized PI has good bending resistance and maintains conductivity of more than 50% even if it is bent 500 times with a radius of 2 mm.