+ Post New Thread
Results 1 to 5 of 5
  1. #1
    Junior Member level 1
    Points: 2,060, Level: 10
    Achievements:
    7 years registered

    Join Date
    Mar 2007
    Posts
    19
    Helped
    0 / 0
    Points
    2,060
    Level
    10

    fr4 impedance per cm

    Hello Friends,
    I 'm trying to find the impedance of a rectangular 10*1 cm^2 of a pcb FR4
    two layer copper 0.025mm per layer and h=1.55mm
    I tried to measure but that was not satisfactory and i 'm trying to
    compare measuring the impedance and then I will find the dielectric constant.

    Thanks

    •   AltAdvertisment

        
       

  2. #2
    Advanced Member level 4
    Points: 15,672, Level: 30

    Join Date
    Feb 2002
    Location
    USA
    Posts
    1,371
    Helped
    410 / 410
    Points
    15,672
    Level
    30

    fr4 characteristic impedance

    A slab of PCB material doesn't have a characteristic impedance - a trace etched on the PCB material has a characteristic impedance. The impedance of a trace on a PCB can be measured and is dependendent on the width of the trace, the thickness of the copper used on the trace, the frequency of the applied signal, the dielectric constant of the PCB material, and the distance from the trace to the nearest return copper structure (usually an underlying plane).

    To measure the characteristic impedance of a trace on a PCB, you can use several different instruments - a time domain analyzer, a vector network analyzer, or a crude setup using a pulse generator and an oscilloscope. No matter what instrument setup you use, the technique is basically the same - you send a pulse down the trace, and look to see how it is changed by the trace.

    There is an article that might be of help at: http://www.home.agilent.com/upload/c.../All/GTL91.pdf



    •   AltAdvertisment

        
       

  3. #3
    Junior Member level 1
    Points: 2,060, Level: 10
    Achievements:
    7 years registered

    Join Date
    Mar 2007
    Posts
    19
    Helped
    0 / 0
    Points
    2,060
    Level
    10

    fr4 impedance

    That 's Right , I was thinking in a trace etched on the PCB material, but i don`t know if there is a formula for the theoretic characteristic impedance like the
    Microstrip Transmission Line Characteristic Impedance.

    regards



    •   AltAdvertisment

        
       

  4. #4
    Advanced Member level 4
    Points: 15,672, Level: 30

    Join Date
    Feb 2002
    Location
    USA
    Posts
    1,371
    Helped
    410 / 410
    Points
    15,672
    Level
    30

    fr4 pcb impedance

    There is a discussion of impedance calculations in the following paper:http://www.polarinstruments.com/supp...ts/IPC1999.pdf

    There is a slide presentation that may be useful at:http://www.speedingedge.com/PDF-File...0Impedance.pdf



  5. #5
    Member level 2
    Points: 2,909, Level: 12
    heedavid's Avatar
    Join Date
    Apr 2005
    Posts
    52
    Helped
    17 / 17
    Points
    2,909
    Level
    12

    fr4 four layer trace impedance

    Dear roderick81,

    I've replied to your other thread. Do see:

    https://www.edaboard.com/ftopic264338.html

    Best regards,
    Dave



--[[ ]]--