Investigation Of Electromagnetic Behavior On Interconnection Structure And Material For Printed Circuit

Electronic products with high-frequency and high-speed development,cause serious signal integrity(SI)problem of printed circuit board(PCB)as the function of interconnection carrier.In this way,SI improvement of PCB turns to one of the research hotspots in order to improve the signal transmission quality of electronic products.Electromagnetic interference is one of the important causes of SI outside the PCB.In addition,the quality of the interlayer interconnect structure and the roughness of transmission line affect the SI inside the PCB.To solve these problems,this work focuses on the research on materials and manufacturing technology as follows.Electromagnetic shielding materials can effectively suppress the electromagnetic interference outside the PCB.A nitrogen-doped carbon(PNC)material with three-dimensional porous structure was fabricated with activation and high-temperature pyrolysis using biomass bamboo fungus as carbon source.Thereafter,Fe₃O₄ magnetic nanoparticles were deposited on the carbon with hydrothermal method to form PNC/Fe₃O₄ composite.In the range of 8?12 GHz,the electromagnetic shielding effectiveness of above composite can reach up to 57.9 d B for the reference to suppress PCB electromagnetic interference.Blind mircovias are the key interconnect structure inside the PCB.but the reliability of signal transmission is dependent on the quality of the blind mircovias.In this study,the CO₂ laser direct drilling process is used to make blind mircovias.However,laser absorption rate of copper surface plays an important role in drilling efficiency.The copper was roughened with some surface treatments called medium roughening,super roughening,brown oxidation and black oxidation respectively before CO₂ laser direct drilling process was used to drill the roughened copper surface.The drilling experiment results showed that the copper surface could be ablated by CO₂ laser after super roughening,but blind mircovias with poor drilling quality could not meet the production requirements.However,the drilling quality of blind mircovias was better from brown oxidation and black oxidation while black oxidation led to little defects.After copper filling,blind mircovias with the treatment of black oxidation could match the interconnection and signal transmission quality of PCB.A close relationship was found between transmission line roughness and signal transmission loss.Effects of four different brown oxidation solution A,B,C and D,as well as different types of copper foils and different grades of copper clad laminates were investigated on signal transmission loss and reliability.The insertion loss increased with the increase of the surface roughness for the transmission line.The roughness of the transmission line is the smallest with the treatment brown oxidation solution C,thereby leading to the peel strength of 0.56 N/mm,and the insertion loss of-31.326 d B/m@20GHz.In addition,brown oxidation solution C was used to roughen different copper foils.It was found that HVLP3 copper foils had the minimum roughness value among all hyper very low profile(HVLP)copper foils.The structure stacked with M7 grade laminate and HVLP3 copper foils exhibited a peel strength of 0.65 N/mm and an insertion loss of-55.567 d B/m@20 GHz.Above stacking structure could be suitable for the production of high frequency and high speed PCB with an SI improvement of the PCB.