Research Of Key Technology For High Speed, High Density PCBs

With signal transfer speed increased and package size reduced gradually, high-speed, high density PCB technology has become difficulty and hotspot in electronic design area. Because of that, this paper studies the key technology and methodology of high speed, high density PCBs.At first, theory and implemention of high-speed signal transmission, including transmission line's theory, signal integrity and power integrity, was introduced. Reasons that result in loss are stressed. Also, the calculating formulation of characteristic impedance is deduced and analyzed. As a result, impedance must be plurality and correlative with frequency. Thereby, many factors ignored in low speed designs are considered so that impedance is controlled more accurately and better terminator matching.Aimed at applications and development of embedded technology for PCBs, design methodology and materials of embedded planar resistance is discussed. Physical and layout design of planar resistance are implemented. In addition, embedded capacitors, inductances and chips in PCB are studied. Because embedded components have modified the physical structure of the PCBs, method of calculating characteristic impedance, which is the attribute of transmission lines in embedded layers, are discussed with the example of embedded planar resistance. With accurate calculations and adjustment of impedance, signal integrity problems such as termination and reflection can be avoided.Based on the technology of PCB's design in GHz level, high-speed serial differential transmission, design of high-speed connector and via in PCBs are discussed. Physical structure's modification and interconnect of PCBs amplify the effect on signal integrity. Varies parasitic phenomenon and EMI become centralized represations of high-speed transmission. The paper makes detailed analysis and discussion of these factors. Rules of via design in GHz level are concluded. Strategies to avoid discontunity affection on PCB designs are presented.At last, IBIS model and SPICE model of device are discussed in the paper. Lossy lines are modeled and simulated with the tool of Hyperlynx software. Aimed at via loss in the condition of high frequency, the effect on PCB simulation of via models is analyzed. Multi-board analysis is the important part of backplane system designs. The paper begins with connector's models, discusses each sections and flow of multi-board analysis. Method how to wrapper SPICE models with IBIS model is introduced in ICX enviorment. Consequently, multi-board simulation of high-speed backplane system is implemented, that contribute to predisquisition of emphasis projects.