In modern days, flex circuit boards have become smaller, faster, and more complicated. Would you like to find out more about how Altium assists its users in the configuration of the board layer stackup for a high speed design? Talk to an expert at Altium.8 Try Sierra Circuits’ new Impedance Calculator Why do you need controlled impedance for flex PCBs? Proper board layer stackup in high speed board design requires the best PCB software, and Altium Designer ® is a good one to get started with. There are however some important considerations for the configuration of the stackup that have been listed here that should be helpful to you. That decision will have to be based on cost, materials and the needs of the design. There aren’t any hard fast rules as to how many layers constitute the best board stackup for high speed designs. Therefore, be sure to construct your board board stackups so that high speed circuitry is not forced to cross plane splits or non-referenced ground planes. This because the return path of the signal has to loop outside of its expected path instead of flowing along next to the routed trace. When a return path is diverted, it can cause noise and crosstalk in the. This is because a high speed transmission line routed over a plane split will divert the return path for that signal. When doing this In a high speed design, special care must be executed. This is a practice in mixed signal designs where a single plane layer may have multiple splits. One alternative is to split the ground and power planes to carry different voltages. This can be incredibly expensive or impractical to build. I also recommended that you incorporate a complete power plane into the design.Īlternatively, when you are working with several regulated voltages, giving each voltage its own layer and ground plane can result in too many plane layers in the board stackup. Power and Ground on a PCB Stackup requirements for ground and power planesĪs we mentioned earlier, effective high speed routing using microstrip or stripline routing methodologies require a least one complete ground plane. For example, dual stripline requires that you surround two adjacent internal signal layers with ground planes. There are also other types of stripline which you may need to consider as well. When routing stripline your board stackup will have to include ground planes on both sides of an internal signal layer where the high speed routing is being done. When routing microstrip, your board stackup will have to include a ground plane next to the external routing layers of the high frequency board.
When planning your board stackup for a high speed design, you will need to take into account these routing methods. The transmission line is a routed trace on an internal signal layer which is embedded in dielectric material balanced between the two planes. Alternatively, stripline has a referenced ground plane both above and below the transmission line. It has a transmission line, which is a routed trace on an external layer of the board, that is separated from its referenced ground plane by a layer of dielectric material. Microstrip is the simpler methodology of the two.
The physical structure requirements of these routing methods will have a great impact on your board stackup decisions. These methods are designed so that a high speed signal running through a routed trace will have the correct physical structure for its return path. High speed signals are most often routed using either microstrip or stripline methodologies. Stackup requirements for high speed routing Not only is the selection of printed board board materials important for impedance, dissipation and other signal characteristics, but the order and number of layers of those materials play a vital role as well. High speed PCB designs have tighter signal integrity requirements, and constructing your board for them becomes part of the overall signal integrity equation. A particular high point for me was when I began working on dense multi-layer high speed board designs. That being said, as my skills increased, so did the complexity of the boards that I designed. Test boards and control panels, I cannot tell you how many simple 2 and 4 layer boards I have designed in my career. Most of them were small low speed designs with very few restrictions on them. I’ve been designing boards for a long time however when I began my career, the boards I designs were pretty simple.
0 kommentar(er)
