Multilayer circuit board with grounding grids and method for controlling characteristic impedance of the multilayer circuit board

摘要

A multilayer circuit board has a first insulating layer, a first grounding grid layer and a transmission layer. The first grounding grid layer is formed below the bottom surface of the first insulating layer and has multiple grids. The grids are arranged in an array pattern and are made of metal, and each grid has a centerline and a shape. Centerlines of adjacent grids are separated by a first distance. The transmission layer is formed on the top surface of the first insulating layer and has at least one transmission line and a datum line. The datum line corresponds to the centerline of one of the grids and is separated from the transmission line by a second distance. The second distance can be quarters of the first distance. Since the characteristic impedance is controlled by varying the second distance, different second distance results in different characteristic impedance.