Study On The Manufacturing Technology And Signal Integrity Of 5G High-Speed Printed Circuit

With the rapid upgrading of 5G technology and the diversified development of application scenarios,PCB technology has tended to be high-frequency,high-speed and high-density,which creates a serious challenge to the key technologies and processes in PCB manufacturing.In the process of 5G high-speed PCB manufacturing,how to reduce the width and spacing of lines to avoid line side etching in the etching process and how to realize high thickness-to-diameter ratio through-hole interconnections to avoid electrical interconnect failures or unstable signal transmission due to sealing holes,holes without copper and other problems.At the same time,due to the increasing bandwidth and single-channel transmission rate of 5G,the signal loss and attenuation quality of the transmission path in the high-speed interconnect is more demanding.It is necessary to conduct a systematic study of various factors affecting the signal transmission of the PCB,and develop a more conducive to improve the stability of the signal transmission of the process path.In this paper,fine line production,through-hole electrodeposition interconnect,signal integrity control of 5G high-speed PCB are investigated by electrochemical,quantum chemical and material characterization.Meantime,the construction of PCB manufacturing workshop intelligent management and decisionmaking platform is proposed.The main contents are as follows:(1)The effect of imidazole derivatives corrosion inhibitors on the etching process of5 G high-speed PCB fine lines was studied.The orbital energies,electrostatic potentials,and adsorption on the copper surface of the three corrosion inhibitors,N,N’-thiocarbonyl diimidazole,N,N’-diimidazolyl ethylenediamide,and 2,5-bis(1H-imidazol-1-yl)terephthalic acid,are investigated on the basis of quantum chemical calculations and molecular dynamics simulations.The results showed that the phenyl and imidazole rings and heteroatoms in the corrosion inhibitor molecules can be active sites to form a stable parallel adsorption structure on the copper surface.In addition,2,5-bis(1H-imidazol-1-yl)terephthalic acid molecule has the strongest adsorption on the copper layer.The polarization of the three corrosion inhibitors was further investigated by electrochemical tests.SEM characterization and copper etching showed that the corrosion inhibitors could effectively improve the degree of copper surface corrosion,enhance the copper surface flatness,and improve the copper line side corrosion phenomenon.2,5-bis(1H-imidazol-1-yl)terephthalic acid additive was able to achieve an etching factor of 18.07 in line fabrication with a line width/line spacing of 35 μm/35 μm.(2)The effect of azo dye additives on the electrodeposition of copper in 5G highspeed PCB through holes was investigated.Firstly,the quantum chemical calculations were used to obtain the front line orbital energies and surface electrostatic potentials of the three azo dyes,which indicates that the additive 3G-P had the lowest ΔE value and the highest molecular surface electrostatic potential.The weak inhibition of the three azo dyes in copper electrodeposition was further investigated by cyclic voltammetry.Through-hole electrodeposition filling experiments were carried out in a Harlem bath,and the results showed that all three additives were able to improve the uniformity of the plating solution.The TP value of through-hole with a thickness-to-diameter ratio of 10 was increased to 92.03% by adding the additive 3G-P.XRD tests showed that the optimal orientation of the electrodeposited copper crystals did not change,which was conducive to improving the corrosion resistance and reliability of the copper layer.The surface flatness of the plated copper surface was also enhanced in the electrodeposited solution with the additive 3G-P by SEM and roughness tests.(3)The influencing factors of 5G high-speed PCB signal transmission integrity were studied including PCB substrate materials,signal transmission lines,hole design.The technological breakthrough of 0-Stub technology was firstly developed,which means the value of Stub was controlled to 0.Substrate materials on the signal transmission can not be ignored and ultra Low loss substrate materials have the least impact on signal loss,especially in the high frequency signal transmission.The impedance value and signal transmission loss decreased with the increase width of line.The lager the line spacing and the curve length(per inch),the lower the effect of signal insertion loss.The impedance and signal insertion loss show an overall upward trend with the increase size of the PAD and number of curve nodes.Large or small An-ti PAD design will have a large impact on impedance and signal insertion loss,and the optimal size of An-ti PAD is about 0.7 mm or 0.8 mm.Compared with line width uniformity,tear-drop design has significant impact on signal insertion loss.The stability of signal transmission can be promoted by improving the uniformity of copper plating on the hole.The signal transmission can be affected obviously and the shorter the Stub value,the more favorable it is for signal transmission.Notably,0-Stub technology route was successfully developed,which has been applied to 5G high-speed communication PCB manufacturing.anti-plating ink was used and discontinuous chemical copper plated hole was formed because of the depolymerization hydrolysis of ink.The integrity of high-frequency PCB signal transmission was effectively improved with by using 0-Stub technology.The reflection problem of 5G high-speed signal communication between different PCB layer was completely solved.(4)Based on the process of the PCB manufacturing including PCB product design,scheduling,manufacturing and inspection,the overall structure of the PCB manufacturing workshop intelligent management and decision-making platform were established.The technical path of PCB manufacturing intelligent management and decision-making platform composed of decision management part,manufacturing management part,intelligent perception part and intelligent equipment part is proposed.Specific implementation paths and programs are proposed in the perspective of intelligent equipment part,intelligent perception part,manufacturing management part,and decision management part respectively.Also,the full automation and unmanned PCB production is proposed by building a robot cloud service prediction and health management platform.The workshop layout,design optimization and process reengineering were modified by Flexsim or Witness simulation software.In the end,three typical PCB application cases are introduced in details from the perspective of PCB intelligent production,information acquisition and processing,process optimization and intelligent decision-making.