The signal transmission characteristics of embedded microstrip transmission lines over a meshed ground plane in copper/polyimide multichip module

The high-speed digital signal transmission characteristics of a microstrip transmission line in a meshed ground plane environment were studied. It is found that ground plane geometry significantly affects the degree of crosstalk noise between two adjacent signal lines and the characteristic impedance of a transmission line. A signal conductor over a meshed ground plane exhibits less degradation in rise time and voltage amplitude, compared to a line over a solid ground plane, due to the lower line capacitance and lower conductor loss. However, the longer current path in the case of a meshed ground plane increases the overall line inductance which results in a slower propagation velocity. A ground plane with optimum geometric configuration, in mesh pitch and aperture, is chosen that meets system level performance requirements while still being compatible with processing constraints. The impact of transmission lines with meshed ground plane on multichip module design for digital applications is also discussed