| Data are transmitted through conductors such as copper wires in electrical interconnection,the signal modulation object of which is voltage generally.On the other hand,data can be sent in the way of optical interconnection through the optical fiber,the optical waveguide or the air,and the signal modulation object of which is generally light intensity.Along with the rapid improvement of the electronic equipment integration and the increasing of service frequency,the signal transmission rate based on copper wires in the electrical interconnection has reached the physical limit.It has been difficult to adapt to high rate signal transmission,especially when the microstrip line is used for high speed signal transmission on the printed circuit board(PCB).The performance of the entire system will be constrained by the interconnection ability.This is recognized as the interconnection bottleneck.Photoelectric interconnection technology and the photoelectric interconnection printed circuit board assembly(PCBA)emerged as the times require in response to this enormous challenge.For excellent high speed signal transmission advantage,photoelectric interconnection PCBA has become a hot topic at present.Combined with the actual need of scientific research projects and related sample development,the overall design had been carried on for the photoelectric interconnection PCBA embedded silica fibers.The research was mainly focused on circuit layout design,general mechanical structure design,structure of the silica fiber embedded design,optical coupling components design,simulation evaluation of optical path coupling efficiency in the service environment and the experimental verification,etc.Four key technologies have been break through.The key technologies included chip layout optimization technology,mechanical structure design technology of embedded silica fiber,coupling loss and compatible technology between silica fiber array and optical transceiver module,and simulation evaluation technology of optical path coupling efficiency in the service environment.The research obtained practical results of universal significance.It also was verified by the application of actual products.The main research contents and research results are as follows.A new implementation scheme of the photoelectric interconnection PCBA embedded silica fibers was proposed in the second chapter.The circuit design,the layout optimization design and the overall mechanical structure design were carried out combine with the examples.In the process of layout optimization design,the layout optimization algorithm based on genetic algorithm(GA)is improved in order to adapt to chip layout demands for PCBA embedded silica fibers.Firstly,the high frequency weighting coefficient is added to the fitness function to ensure the shortest connection length of high frequency circuits in the process of layout optimization.Secondly,the alignment constraint and the spacing constraint for the photoelectric interface of the photoelectric chips were added in the fitness function to ensure the alignment and the embedded silica fiber.It is convenient for the parallel wiring of silica fiber.The applicability and validity of the photoelectric interconnection PCBA chip optimization algorithm based on improved GA were verified by the example application.A design method and a new structure of silica fiber embedded are presented in the third chapter.The specific steps are described as follows.Firstly,the finite element models were established for different silica fiber embedded structures.One of fiber embedded structures is selected founded on the analysis of the maximum stress value of the fiber and the maximum position offset of the fiber end face.Then,based on the finite element simulation of the laminating process,two kinds of influence curve were obtained.One is between the filler material parameters and the fiber stress.Another is between the parameters of groove sizes in fiber embedded structure and fiber stress.Next,matching design of the material characteristics was carried out for three kinds of filler glue,and the depth and the space were optimized for the grooves.Finally,an optimized fiber embedded structure and a matching filler glue type were designed.This method is applicable to the structure design that fiber embedded for the single fiber or array silica fibers in photoelectric interconnection substrate,and solves the program of design method vacancy for optical fiber embedded in the photoelectric interconnection substrate.Based on the fracture mechanism of silica fiber,a new type of groove structure that silica fiber embedded was proposed through theoretical analysis and thermal solid coupling simulation analysis.The key dimensions of the fiber embedded structure were determined based on silica fiber tolerance and groove cutting precision.For the groove structure,not only the requirements of the fiber positioning could be met,but also the stress concentration of embedded fiber could be reduced effectively.The study provides a novel fiber embedded structure scheme for the photoelectric interconnection substrate.A new optical coupling element with high coupling efficiency is designed in the fourth chapter.It is suitable for the photoelectric interconnection PCBA embedded silica fibers,and compatible with surface mounting technology(SMT)process.Firstly,the main factors that influence coupling efficiency of coupling components were determined through orthogonal design and simulation analysis.The factors include the thickness of the coupling lens and the distance between the coupling lens and optical transceiver element.Then,based on coupling loss minimization,the coupling lens structure was optimized using ASAP optical simulation software.The optimization result shows that the coupling loss is lower than the existing coupling component.Next,based on the coupling alignment theory of overlap integral method,1 d B misalignment tolerance of between the coupling element and the optical transceiver was obtained through simulation analysis.Furthermore,positioning tolerance of the coupling element was determined and the proper assembling process was selected based on the positioning tolerance.The assembly process of the coupling component is fully compatible with the existing SMT process,which can easily realize the assembly precision and guarantee the photoelectric coupling index requirements.The simulation evaluation method of optical path coupling efficiency in the service environment is presented in the fifth chapter for the photoelectric interconnection PCBA embedded silica fibers.The current circuit components service environmental adaptive test simulation research mainly concentrated on the solder joint.The research related optical path coupling efficiency for the photoelectric interconnection PCBA embedded silica fibers in the service environment has not been reported.The research solved two problems.One is coupling misalignment of the optical transceiver module had occurred or not under the condition of the service environment.Another is how to evaluate the optical path coupling efficiency under the service environment.In the implementation of this method,there are two innovations.First,a simulation model of optical path coupling efficiency is established.It solves the coupling efficiency evaluation problem of the entire optical path when the misalignment occurred between optical transceiver components and coupling components at the same time under the service environment.Second,finite element model was established for the photoelectric interconnection PCBA.In order to extract the relative offset between the optical transceiver and the coupling lens center,the node was set up at the optical transceiver center and the coupling lens center.It provides a basis for further study of the impact of the service environment on the optical paths coupling misalignment.The method could be highly enforceable and save a lot of test cost and time in the evaluation process.The evaluation results provide a quantifiable index basis for further improvement of product design. |
PDF Full Text Request