Four-Layer High-Speed PCB Design May 29, 2007
When minimum cost and high-speed are required, a four-layer board may be the answer. High-Speed PCB design generally requires controlled impedance traces and good power and ground planes in order to meet signal integrity and power integrity requirements. Four-Layer PCBs are essentially made of 2 two-layer hardboards “glued” together with a pre-preg spacer in between them. The thickness of the pre-preg is not as well controlled as that of the hardboards. So, for good controlled impedance traces, it is recommended to use the layers separated by hardboard as signal and ground. The layers separated by pre-preg can be used as power and ground.
Thus, a recommended stack up for a high-speed four-layer board is; (more…)
PCB Stack-Up Design And Impedance Calculator May 12, 2007
Review: A new PCB stack-up design and impedance calculator is available for download from Istvan Nagy (see link below). It is a full-featured Excel-based tool that helps plan the PCB stack-up so that controlled impedance traces can be effectively implemented. It covers both single-ended and differential traces and is based on the equation s from IPC-D-317A. It allows one to see the range of impedances that are possible for a given layer stack-up. It also has pre-distortion calculations to support high-speed compensation, a unit changer, and a materials library.
Right-Click, Download and Save the Excel tool here:
layerstack_planningoriginalipc.xls
Istvan Nagy’s home page:
[Sorry, link had to be removed due to content issues.]
Do you have a favorite stack-up and impedance calculation tool? Let us know about it in the comments below.