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How to create pad on bottom copper layer only

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3 comments

  • Boss .

    Why do you not want pads on the top layer? I have in the past created boards this way until I realised just how good the cheapest boards from China were! 
    As far as I'm aware you cannot remove pads from the top copper layer, but I did not have a problem with this. You have the option to use the through hole lead on some pins by soldering both sides to use as a top to the bottom copper connection (i.e. simulating a plated hole) which you will need to connect to the tracks of SM components on the top copper.

    The only difference between a plated and non-plated holes is the drill size used by the manufacturer which does not impact on home produced designs. As long as you route your tracks on the bottom layer and select where you can connect to the top copper you should not have any issues in my opinion.

    Provide some further details if I have misunderstood your requirements.

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  • Brian Keen

    I decided to live with pads on the Top Copper layer - although it did result in some problems when I etched the board:-

    As I'm making a double sided board that operates at high frequencies, I thought it would be a good idea to include a ground plane on the Top Copper layer.
    I did this using copper pour - a feature I had not before.
    I found the default Pad to Shape spacing between the pads and the ground plane copper pour area was too small.
    I tried to change the rules to increase the gap but this resulted in a number of Pad to Shape warnings on the Bottom Copper layer when I ran a Design Rules Check.
    As a compromise, I ended up setting the Pad to Shape spacing to 20 tho' although the gap to the ground plane still looked a bit small.
    When I etched the board and tested it for continuity, sure enough I found three or four pads on the Top Copper layer had remnants of copper shorting them to the ground plane.

    It needed some careful surgery with a scalpel to correct the faults.
    That's one of the problems when making DIY boards at home: The board manufacturing process is not well controlled.

    Because the ground plane copper pour gap applies over a wide area, the chances of shorts after etching is a lot higher than other Pad to Shape or Track to Shape sections e.g. on the Bottom Copper layer.
    A possible solution might be to allow a different set of spacing rules for copper pour.
    That way you could allow a larger gap between Pads and Tack for the ground plane while keeping the rules for other areas tighter.
    In the current software the only way to do this is to temporarily change the rules to give a larger gap, apply the copper pour and then change the rules back before running a Design Rules Check.

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  • Boss .

    You may be able to achieve this as follows.
    Plot your bottom copper as normal.

    Now for top copper go to Design Technology "Pad Styles"

    I set all pads from 60 down to 2 as I'm not sure what will happen at 0.

    The copper pour will be present and all pads will be drilled out (ah, ignore these warnings when you do the above!)

    As all the pads are gone you will need to fill the ones that were connected to the ground plane with a filled copper shape.

    You will need to set pour to tracks etc to what you require before doing the above.
    I would also work on a duplicate copy of the project to get back to the original.

     

     

     

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