Research Of Polymer Assisted (PAMD) High Frequency Dielectric Substrate Metallization Technology

The development of 5G/6G electronic communication technology toward ultra-high frequency,ultra-high speed,and ultra-low latency poses new challenges to electronic substrates'electrical and mechanical properties.High-frequency dielectric substrates represented by glass fiber epoxy resin(FR4)and polyphenylene sulfide(PPS)are considered ideal materials for developing 5G/6G high-frequency communication technologies because of their low dielectric constant,low dielectric loss,and strong chemical resistance.However,FR4 and PPS are limited by the conditions of minor surface roughness and lack of polar groups that can adsorb metal particles,making it difficult to prepare a metal layer with high adhesion strength on their surfaces.Therefore,a simple,efficient,low-cost,and reliable surface metal deposition strategy is proposed to successfully prepare high-quality conductive metallic copper layers on the surfaces of both FR4 and PPS substrates.The details of the research are as follows.(1)This work selected MnO₂-Na₄P₂O₇-H₂SO₄ micro etching treatment of PPS substrate at 60?for 40 min as the best micro etching process through comparative experiments.The surface roughness of the treated PPS substrate was 152.0 nm,and the surface water contact angle was reduced from 76.0°to 42.0°,with a significant improvement in hydrophilicity.(2)The concentrated sulfuric acid micro etching treatment of FR4 substrate at 95?for 40 min was determined as the optimal micro etching process through comparative experiments.The surface roughness of the treated FR4 substrate was 243.3 nm,the surface water contact angle was reduced from 92.4°to 68.4°,and the hydrophilicity was greatly improved.(3)The optimal deposition time of 3.5 h was determined by UV-assisted catechol/tetraethylenepentamine solution for graft modification of PPS substrates and FR4 substrates.The successful preparation of poly(catechol/tetraethylenepentamine)on the substrate surface and the acceleration of its polymerization process by UV irradiation treatment was demonstrated by FTIR,XPS,SEM,and contact angle tests.At the same time,the introduction of a large number of phenolic hydroxyl and amino groups on the surface of the substrate allows the modified substrate to maintain good hydrophilicity despite the reduced roughness of the surface and to produce a strong adsorption effect on the active metal particles,thus ensuring the bonding strength between the metal layer and the substrate.(4)The formaldehyde chemical plating system was used to prepare the metallic layer on the surface of the substrate,and the surface morphology,chemical composition,and properties of the prepared metallic copper layer were characterized under optimal conditions.It was found that the surface of the prepared metallic copper layer was bright and flat,uniform and dense,with high crystallinity and no apparent impurities.In addition,the metallic copper layer also has good electrical conductivity and mechanical properties.The resistivity of the copper metal layer on the surface of the PPS substrate is as low as2.7??·cm,which is only 1.6 times that of the bulk copper sheet,and the resistivity of the copper metal layer on the surface of the FR4 substrate is only 3.1??·cm.The bonding strength between the modified substrates and the deposited metallic copper layer both meet the ASTM D3359-02 standard of 5B grade.