Research And Application Of Surface Alkaline Oxidation Technology For Copper Foil Of PCB Laminate

The 5th generation mobile communication technology has tremendous application prospects in artificial intelligence,mobile Internet,etc.,and the PCB(Printed Circuit Board)applied to this field have higher technical requirements than conventional PCB products in terms of transmission frequency band,transmission time and transmission loss in high-frequency signal transmission.As far as PCB manufacturing is concerned,achieving the effective control of the surface roughness of copper foil in the manufacturing process is one of the key points to meet these high technical requirements,and it is also a hot spot in the current industry research.Therefore,conducting the research on the surface treatment technology of copper foil in PCB manufacturing not only has scientific significance,but also has industrial production application value.At present,the existing surface treatment technology in the PCB industry is difficult to achieve both the bonding force between the layers of the multilayer board and the reduction of the high-frequency transmission signal loss.In response to this situation,based on the experimental fact that the corrosion rate of copper in some alkaline systems is lower than that of the existing browning process used in the PCB field,Na₂O₂ was used as the copper oxidant in this paper,and by adding silicate,molybdate,etc.separately to improve the chemical composition of the dielectric film and improve the surface bonding force and other properties,forming a new type of alkaline oxidation treatment technology for the surface of the copper foil on the PCB substrate.By forming an organic-inorganic metal oxide film layer on the PCB substrate,the roughness of the copper foil and the interlayer bonding force can be both controlled.The composite film layer was bridged by Cu₂O,CuO,CuSiO₃ and N-based organics,and the film layer has good hydrophilicity,which can obtain a small surface roughness on the surface of the copper foil while making the bonding force between copper foil and the dielectric layer resin meets the IPC-TM650standard.The developed alkaline oxidation treatment technology for the surface of the copper foil on the PCB substrate includes alkaline washing,pickling,copper surface alkaline oxidation treatment.Through the study of the bonding force between copper foil and dielectric layer and the surface roughness test of copper foil,the optimal test conditions of the copper foil treated with the alkaline oxidation treatment technology under different conditions were obtained.Under the optimal experimental condition,the bonding force between copper foil and resin can reach 1.20 N/mm,and the surface roughness of copper foil is 0.22?m,which is better than the existing browning technology.By the test of the electrochemical impedance spectroscopy(EIS)and polarization curve for the copper surface treated by the self-developed alkaline oxidation treatment technology,the corrosion mechanism of the treatment solution in the research system was explored.The alkaline oxidation treatment technology under the optimal test conditions was applied to30?50?m fine circuit and six-layer high-frequency PCB.Compared to the traditional browning process,very small surface roughness of 30?50?m fine circuit and the lower8 d B/m@10 GHz and 14 d B/m@20 GHz in high-frequency applied to six-layer high-frequency PCB were obtained under the optimal test conditions with the alkaline oxidation treatment technology.Therefore,the alkaline oxidation treatment technology is more suitable for the production of high-frequency PCB,and it has an outstanding development prospect.