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SMD pads - creating vias underneath?



  • Brad Levy

    For surface mount pads that should be on the bottom layer, change the layer from [All] to [Bottom], instead of [All] to [Top].

    Since you were changing the pad layer after you had connect a trace to it, DS PCB add the via to keep the trace and pad connected. It won't add the via if the pad you are changing from thru-hole (layer [All]) to surface mount ([Top] or [Bottom] layer only) is being set to the same layer as the trace(s) connected to it. You can have surface mount components on each side of the board. And two surface mount components can overlap each other, as long as they are not on the same side of the board.

    Note that next time you can change the layer of the pad you are about to place from [All]) to [Top] or [Bottom] by pressing (or right-click and select Change Layer...) to set the layer after clicking on the Add Pad tool, before placing the pad, just like you changed its style.

    If you have a trace on one layer and want to connect it to a surface mount pad on a different layer, you do need a via to get there - but you don't usually want the via to be right on top of / coincident with the pad. There are multiple ways to easily add the via while drawing the trace, but that is a different question than your original one, and not specific to SMD pads. Ask (or check the built-in help) if you need more help.



  • Brad Levy

    Another helpful tip. If you don't already have the Interaction Bar turned on, press F9 or select View > Interaction Bar to turn it on.

    With the Interaction Bar on, you can click on the Layers tab at the bottom of the bar, then turn viewing of different layers off and on by clicking the check-boxes next to the layer names.

    Turning off viewing of the Top Copper or Bottom Copper will hide any traces segments and pads that are only on the layer you are turning off, making it easy to see if you have the pad on the wrong layer(s).

    If you have solder mask or paste mask layers defined in your design technology, there will be separate check-boxes in the interaction bar for showing/hiding those as well. Hiding top copper doesn't hide the top solder mask or paste mask layers. So if you want to see only the bottom stuff, make sure each top layer is un-checked in the interaction bar.

    You can also control layer visibility in the Colors dialog (menu: View > Colors, or shortcut C).
    The colors dialog takes a few more steps for some things, but lets you show/hide all layers on a give side with one action. On the Settings and Highlights tab of the Colors dialog, there are check boxes to Merge Colors for Shapes and for Tracks. These will make it easier to see where traces on both sides of the board overlap.


  • Richard Saville

    Thanks a lot for taking the time to comment, really useful stuff. I think I'm about there now, pads seem to all work well on top copper. I think the via/SMD footprint thing just didn't click with me initially. Cheers.


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