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Questions about the "Layer Stack Manager" options

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  • Questions about the "Layer Stack Manager" options


    I have some questions regarding the "Layer Stack Manager".

    1- I'm using the material Rogers RO4003C for my PCB and I noticed that this material is not present in the "Material" list, so I added the name on the the column. Is this the correct approach for this case?

    2- In the "Type" column there are the following options: Core, Prepeg, Adhesive, Stiffner and Dielectric. Which one should I choose?

    3- What value should I put in the Dielectric Constant (Dk) column? The datasheet for Rogers 4003C has 2 values 3.38 and 3.55 (I guess its 3.55)

    4- Should I also complete the Dissipation Factor (Df) column?

    5- The "Properties" of the "Impedance Profile" has the following options in Type: Single, Differential, Single-Coplanar and Differential Coplanar. I need to use "Grounded Coplanar Waveguide" to route some trucks. The closest one seems to be "Single-Coplanar" but its obviosly missing the grounded. Is it ok if I use this option to calculate the impedance?


  • #2

    i will try to explain as much as i can. You can find every needed information in material's datasheet. Which are mostly DK, Df, Td and Tg.
    1) If your material added in the Altium's database you just suppsoed to pick it and the values loaded directly. If you can't find your material in the list then there is no need to type the exact name. You should fill the values. In Altium designer or their website you can chech how the calculations made and how the constants affect in various considerations.
    2) The material is a prepreg so it does have a dielectric constant. you will have layers above and below of it and it's purpose is to seperate them (with respect to it's strongness which is Dk.)
    3) The "strongness" of the material differentiates under different frequencies. So you should consider the Dk value with respect to your signals' frequencies. I would use 3.38 because I assume that you will use striplines but it could be asked to firm.
    4) Df is affects loss in signal simply. And mostly effective on high speed (~10Ghz) signals mostly. But just type it down in the related column. Not a big deal.

    I am leaving "5" to someone else.

    I hope above would help you a bit. You can chechk this link:
    FR4 is by far the most popular set of PCB substrate materials. Here is how FR4 dielectric constant and your material properties will affect your next PCB.

    In this OnTrack episode we'll talk about Dielectric constant (Dk) and the difference between Design Dk & Process Dk. How datasheets can be confusing and can impact your design? Listen in for more.

    Have a good designing.


    • #3
      5) That depends entirely on you. Will you use ground on those planes?
      Discussion with Eric Bogatin about why return currents flow under tracks ... and more ...Links:- Eric Bogatin:


      • #4
        This will not directly answer your question, but, it may help. I only fill out dimensions and Er (for visualization and stackup table). We always agree on stackup with specific manufacturer - and different PCB manufacturers may use different materials. So, it is not important what is in Altium - maybe only if you use it to calculate impedance. But, I do not use Altium to calculate impedance either, PCB manufacturer has more accurate data and that data should be followed.

        2) My video about FLEX may answer this your question: