Analysis and design of via and flip chip interconnects

This dissertation presents the analysis and the design of via and flip chip interconnects using finite-difference time-domain (FDTD) method with emphasis on microwave circuit applications. Objectives of the research work include evaluation of bump (or via) reflection and insertion loss, reconfiguration of the transition connects to improve and optimize the overall package performance, development of an accurate equivalent circuit model of the transition discontinuity over a wide frequency band, and investigation of the mutual coupling effects on the overall package performance. Novel designs have been developed and presented to reduce the effects of package discontinuities and asymmetry. Staggered designs have been found to reduce reflection and insertion loss over a broad band of frequency. An optimum design is presented to minimize losses and improve matching. Effects of asymmetry on package performance has been also reduced by incorporating the above designs.; The S-parameter of a flip chip package can be computed using the FDTD model and are used to develop an equivalent circuit of transition discontinuity over a wide frequency band. A general and accurate equivalent circuit model has been developed and presented. In this circuit model, a statistical analysis is used to compute the value of the circuit elements. Also, losses in the flip chip package including substrate and radiation losses are represented by simple functions vs. frequency. Substrate loss of the chip and the mother board is due to excitation of surface waves. Radiation loss is attributed to radiation from the discontinuity (bump or via). Conductor and material losses are neglected in this circuit model. The equivalent circuit model presented in this dissertation significantly simplifies the simulation of complex flip chip packages using commercial circuit solvers to predict the overall performance of the package. A parameteric study of the equivalent circuit model for different configurations has been performed and presented.; Finally, mutual coupling effects in different package configurations have been investigated, modeled, and presented. This includes mutual coupling effects in a single transition multiple lines package (STML) and multiple transitions single line package (MTSL). In STML package, mutual coupling effects due to the close proximity of signal lines in a stripline package have been evaluated. This includes mutual coupling between two cross lines and two parallel lines in presence of via interconnects. Mutual coupling effects in MTSL package have been also studied. A general and accurate equivalent circuit model of MTSL package discontinuities has been developed and presented. The main building blocks of this circuit model (MTSL discontinuities) are the equivalent circuit model of STSL discontinuity. A cascaded network of two stages of STSL equivalent circuit model can be used to accurately model the effects of the transition discontinuities. These stages are separated by a transmission line to represent the multiple reflections in the circuit model. Good agreement has been observed between the equivalent circuit model and the rigorous FDTD model in all of the above cases.