Research On Surface Treatment Technology Of Printed Circuit Board Interconnect Pattern And Its Signal Integrity

Due to the rapid development of communication technology and Internet of Things technologies,the miniaturization and high integration of electronic products,and the stable transmission of high-speed signals have posed higher challenges to the manufacturing and interconnection technology of printed circuit boards.The printed circuit board is the carrier of electrical connections in electronic products,and the reliability of its solder joints is critical to the signal transmission between the PCB and the device.Based on the surface treatment technology of PCB graphics,this paper studies the influence of surface treatment technology and soldering on signal integrity from the perspective of the interconnection solder joints between the PCB and the device.It is planned to systematically study the influence of solder joints on the signal after the surface treatment of different graphics,and provide some new ideas for the research of signal integrity under high-speed signal transmission.Due to the high sensitivity of M6G-level materials to signal transmission,this paper uses M6G-level high-speed materials and RTF copper foil to design and fabricate a PCB signal test board for experiments.The design transmission line is a single-line microstrip line on the surface.The surface roughness and signal transmission insertion loss of transmission lines with different surface treatments are compared.Research has proved that among the four surface treatments of bare copper and OSP,electroless silver plating,and electroless nickel gold plating,the roughness after electroless nickel and gold plating is the smallest,but the signal insertion loss after electroless silver plating is the smallest:-46.29 d B/m.Simulate soldering on the surface of the transmission line,conduct solder treatment,explore the growth morphology of the metal compound between the solder and the transmission line with different surface treatments,and compare the insertion loss of the signal transmission in the frequency range of 0-20 GHz after soldering.Studies have shown that the morphology of the Ni₃Sn₄IMC layer grown between the electroless nickel-gold layer and the solder interface is needle-like.It is different from the IMC morphology of the other three surfaces after soldering.The IMC formed between the bare copper,OSP,electroless silver plating layer and the solder is Cu₆Sn₅IMC,and its morphology is hill-shaped.The signal insertion loss comparison results obtained by soldering the transmission lines with 4 different surface treatments,the insertion loss is arranged in descending order:electroless nickel and gold>OSP>bare copper>electroless silver.Aging treatment is often used to simulate the reliability of PCBs in different environments.This experiment explores the growth of IMC after three different aging treatments:cold-heat cycle,constant temperature and humidity,and reflow soldering,and its influence on insertion loss,based on a transmission line that has been surface-treated and soldered.Studies have shown that the thickness of the IMC increases with the increase in the number of hot and cold cycles and reflow soldering.In terms of surface morphology,Ni₃Sn₄IMC will gradually grow from needle-like to layered,while the thickness of Cu₆Sn₅IMC will gradually grow slowly,and the thickness of Cu₃Sn IMC will increase.Constant temperature and humidity treatment has less impact on IMC due to its lower temperature.With the increase of the number of hot and cold cycles and reflow soldering,the signal transmission insertion loss will increase due to the growth of IMC,and the higher reflow soldering temperature has the greatest impact on the increase speed of the insertion loss.Constant temperature and humidity time has little effect on the change of insertion loss.