Diptrace 2 layer pcb mismatch?

Discussion in 'General Electronics Chat' started by sonolink, Sep 25, 2014.

  1. sonolink

    Thread Starter New Member

    Mar 11, 2014
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    Hello
    I just finished my first pcb with diptrace and something odd is happening. I export both layers as pfd and import them into Corel Draw to place them to fit the board and print the whole thing on transparent paper. Of course, I mirror the bottom layer before printing.
    Strangely the screw holes, vias and pads don't match between layers. If I don't mirror the bottom layer they seem to match.....but then the bottom layer would be the wrong way around , right?

    What am I doing wrong?
    Any ideas?
    Thanks a lot for your time and help.
    Cheers
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    PCB programs (AFAIK) all print layers the same way: as if you have X-ray vision and are looking straight down at the board.

    So just printing a layer directly you get a set of printouts that stack up perfect when all are "dark side up."

    If you mirror a layer, well, it's now backwards and nothing will match up.

    You can (and should) prove this to yourself as a sanity test by putting some feature (say a wide trace) on both the top and bottom layers, on one side, and above each other. Then you have a guide to check the printouts.
     
  3. sonolink

    Thread Starter New Member

    Mar 11, 2014
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    Thanks for your reply Ernie. Don't I need to mirror the bottom layer then? I am mirroring it since the copper on both layers are on "opposite sides" and as far as I can tell, when looking at them on the computer you look at both from the same side (from the top or from where the components are).

    Since this is for etching the copper I think I should have a mirrored image of the bottom one but then it won't align...
    What am I doing wrong?

    Thanks again for your time and help

    Cheers
     
  4. crutschow

    Expert

    Mar 14, 2008
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    You mirror them only if you want to view the bottom layer as viewed from the bottom. And, of course,when doing the etching the bottom layer also would be reversed. But when you want to view how the top and bottom layers align, then you view without mirroring. Think about it. When viewing how the layers align, either the top or bottom has to be mirrored, as if looking through the board, since that's how the actual board will be when made.
     
  5. sonolink

    Thread Starter New Member

    Mar 11, 2014
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    So what you're saying is that in order to be able to etch a double layer board I need to print the top layer as it appears on the screen (from the top where the components are) and the bottom layer mirrored since I'll be etching it from tbe opposite side.
    If this is correct, I have the problem that the holes of say an IC don't align between layers when the screw holes are aligned.

    This is getting really annoying
     
  6. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    So what are we missing? Are the dimesnions off, or how are the ICs not aligned? Can you post some pictures of the prints?
     
  7. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    ORLY? How are you aligning the sides when you make this comparison? The ink side of the paper should be out top and bottom.

    I would suggest adding some sort of alignment marks to the artwork to aid lashing them back up together.
     
  8. crutschow

    Expert

    Mar 14, 2008
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    If the all the holes align when you are looking at both with the bottom the mirror image (transparent mode on computer). then they should align when you print them on the circuit board. Don't understand the problem. :confused:
     
  9. sonolink

    Thread Starter New Member

    Mar 11, 2014
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    Guys
    Thanks to all for your replies. I'm out for the weekend but I'll post some pics when I'm back :)
    Thanks again for your time and help
    Cheers
     
  10. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I use DipTrace extensively, but I don't make my own PCBs. If I was going to make my own, I would simply print the top layer not reversed, and the bottom layer reversed - both directly from DipTrace. It works perfectly this way. I think the PDF and Corel Draw steps are completely unnecessary and are the source of your problem. (I haven't used CorelDraw in a loooong time, but from what I remember, it was wonky and a real resource hog.)
     
  11. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Sorry to joint late, but I didn't notice where you said explicitly how you were transferring the image to the board. You do mention "transparency" in your original post, and that could imply that you are using photosensitized PCB boards.

    If that is the case, it is common practice to put the printed side (i.e., toner or ink side) of the transparency against the PCB board for exposure. That practice is supposed to give a sharper image on the board. It also introduces a mirroring. Thus, in printing the TOP layer, you would mirror it. You would not mirror the BOTTOM layer when printing it.

    For all boards, I put a little symbol off the active area so I can easily tell which is the printed side. I also add alignment marks for double-sided boards, tape both transparencies together while observing proper orientation, and then slip the unexposed PCB between the layers.

    Of course, if you are using the toner transfer method, you would follow the same mirroring rules as described above, as that method requires you to have the image against the board's surface.

    John
     
  12. sonolink

    Thread Starter New Member

    Mar 11, 2014
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    Thanks for the input, John and Tracecom :)

    @tracecom
    You might be right about the problems being in the pdf and CorelDraw part of my process.
    The reason why I do that is because I don't know how to print both layers on the same sheet of paper. I use CorelDraw to place the boards so that I just have to cut them off in a single piece and then fold them around the board.
    Is that possible in Diptrace and if so would you mind explaining how to do it please?
    Thanks
     
  13. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I tried to print both sides on the same paper, but didn't succeed. It's probably doable, and you might post the question on the DipTrace forum. Personally, I would just include a couple of registration marks and print each side individually. Good luck.
     
  14. sonolink

    Thread Starter New Member

    Mar 11, 2014
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    Ok. Thanks for your input :)
    Cheers
     
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