Signal Integrity Of Outer Line Of Printed Circuit

With the commercial application of the fifth-generation communication technology,the Signal Integrity(SI)problem brought by the transmission of high-frequency and highspeed signals has become more and more prominent.In addition to the Board level design,material dielectric properties of PCB(Printed Circuit Board,PCB)and fine circuit production technology put forward higher requirements.Surface finishing technology is the last chemical process of printed circuit boards,and the performance of the coating will seriously affect the signal integrity of the outer circuit of PCB.Therefore,the research on the coating layer will become more important.Based on the existing industrial production technology,according to the preliminary design of laminated structure complete high frequency microwave printed circuit experiment board manufacturing.Through the research experiment plate of the microstrip line production technology to explore geometric configurations of the influence of the signal integrity of microstrip line.The result shows that the line width of the microstrip line has the greatest influence on its insertion loss.The solder mask ink can reduce the impedance of the microstrip line and will significantly increase the loss of the microstrip line.Although low-coupling differential line pairs can promote the integrity of signal transmission,they are not suitable for highly integrated printed circuit boards due to their large footprint.This thesis uses HFSS software to explore the simulation conditions of thin coatings,and determines that the simulation of thinner coatings can be completed by defining a finite conductor interface on the surface of the copper layer.The modeling and simulation of microstrip lines with different silver coating thicknesses show that the impedance is increased by about 0.5? compared with bare copper microstrip lines,and the thicker the thickness,the greater the loss of the microstrip line.On the basis of the above research,the circuit design was optimized,and the changes in the surface roughness,conductivity,circuit impedance,insertion loss and other related parameters of the microstrip line before and after the surface finish were compared.Studies have found that surface finishing technology can reduce the surface roughness of the microstrip line,but other surface finishing technologies except for the Organic Solderability Protective(OSP)film technology will cause the impedance and insertion loss of the microstrip line to increase.Compared with the surface finish before,the microstrip line insertion loss increased by 10.6%,74.6%,and 10.7% after the three surface finishing techniques of Immersion Silver,Electroless Nickel Immersion Gold,and Immersion Tin at 25 GHz.The DC resistance value of the microstrip line treated with different surface finishing technologies also increased to varying degrees.According to the resistance increase of the microstrip line,the order of increasing resistance is as follows: OSP < Immersion Silver < Immersion Tin < Electroless Nickel Immersion Gold.At the same time,this thesis also studied the influence of different coating thickness on the insertion loss of the microstrip line.The results show that the microstrip line processed by Immersion Silver technology and Immersion Tin technology will increase the insertion loss with the increase of the coating thickness,and the increase of insertion loss also tends to increase.