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help with PCB layout checking

houandreas

images uploaded.

hi, with your help I finally finished my first board in eagle. But I don't have any experience before, so there might be some mistakes to fix. Here I upload my board and schematic files in my google drive. If anyone could help me with this would be so appreciated.

https://drive.google.com/open?id=1Cm6o7Ets-rg0RCMyVHRzhi6eLX1H9t_D

This board is an adapter board for video signal processing. So it's running high frequcency signals I guess(pixel time 40ns). I read a lot about it but it's more than I can handle for now...

And the placement of those components is quite limited, that is already the best placement I can do. I used autorouter so there is no DRC error for now (I apply the default DRC setting).

here are some net settings for this board, you can also see it in eagle.

signal trace width 10mil, Via 15mil, clearance 10mil.

Power trace width 20mil, Via 20mil. clearance 10mil.

I cannot route if trace width is wider since the LPC connector pins are so close to each other. But this should be enough. Later I will make top and bottom as ground plane and add some via,but now is too late...Again thank you image

imageimageimage

  • Hi Bin,

     

    There are many rich editor tools for presenting your design, such as inserting images inline, and even video..

    You'll get more eyes looking at your question if the images are resized nicely and inserted inline. Right now, you have provided links to files that only work if people have EAGLE installed, and are willing to download files from google drive.

     

    Many people browse the questions using a web browser on all sorts of devices that don't run EAGLE (e.g. mobile phones). You're missing the opportunity to let them see and answer your question.. Anyway it is your decision - I just feel if you don't make it easy for people to understand and explore your question, then you won't get as many answers.

  • in reply to shabaz

    thanks for the tips, I never use other tools , thought those softwares share the same format.... Anyway I uploaded the images.

  • Hi Bin,

     

    After using the autorouter, the DRC check still needs to be done, it cannot be assumed that it will do it for you (it doesn't as far as I understand, but I don't use the autorouter so Im not sure).

    If it passes DRC (and if you've already done the ERC on the schematic) then hopefully it should work to some extent, but it is really up to you to decide if it is adequate - there are many areas for improvement. For example, the power traces may need to be thicker (there is an automated way - assigning net classes - or you can manually change trace thickness) and power plane is helpful. For the latter, 'polygons are used in EAGLE. Also, many traces can be improved. For example, there could be signal buses, and the traces in those could be positioned next to each other, rather than what looks very random currently. It is ok to rip up traces and reattempt, or move some components if possible, to improve the trace paths.

    See here for an animated example of a real PCB, with several iterations:

    image

     

    If you are new to this, then as a suggestion maybe it is worth avoiding the autorouter for now, and manually trying to route it. It will take longer, but you'll learn more about how to use the functionality to place traces to your desired thickness and locations. Also a lot can be learned by looking at existing PCBs.

    I hope this helps.. prototype PCBs are cheap, so you can also learn by just trying it, if the DRC passes. If there are DRC failures then you need to try to understand each failure, since it takes just one to result in an unusable board.

  • yes I will agree to to the previous comments.

     

    DRC checks are very very important to run and understand even. Try to read through the DRC options and understand them with Eagle HELP.


    Some other cautionary measures that I often take are

    • Look for GND islands or big cut outs in the GND and power planes (for internal and external layers). Specially if there is any impedance controlled lines I would make sure there is appropriate GND planes above and below them.
    • Use enough stitching vias on the board.
    • Make sure the traces are not too close together to avoid some basic cross talk issues. Only applicable for critical signal lines.
    • Re-check the Gerbers for proper solder mask solder stop layers.

     

    Cheers image