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Grid question from power supply course

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  • Grid question from power supply course

    Hi Robert,

    I am finding your updated version of the power supply course (Learn Altium Essentials – Second Edition) very useful as I learn Altium Designer (version 19.1.6 (build 110)). I have a few questions with respect to grids in the layout. Here is an example that illustrates the issue:

    The course utilizes a power supply controller (ISL6236A). It is a 32 pin QFP package with the pitch between pads of 0.5mm. You recommend that the center of that device be placed at x=25mm, and y=25mm. This causes the center of all the pads to be off of the 0.1mm grid that you recommend in either the x or the y dimension, one or the other. As an example, you can see in the image below, that the center of pad 22 is at 22.6mm x 25.75mm. The “y” dimension in this case is not on the 0.1mm grid.

    When I draw a short stub from pad 22 before placing the via at the end of the stub, the end of the short stub wants to “snap” to the grid, creating a “jog” in the trace (see first image attached).

    However, in your video, you did not seem to have the same problem. You apparently were able to draw a straight trace from pad 22 (see second image attached). The screen snap-shot I attached was taken from lesson 6 at 1:07:43

    ​Here are a couple of questions:

    1. How were you able to draw the short trace without a “jog”? It doesn’t look like you changed the grid, as it still shows as 0.1mm at the bottom of your screen. Maybe you turned off grid snapping?
    2. I am also studying for the CID certificate and the study materials recommend that PCB layouts be done on a grid. Which PCB features are desirable to be on a grid and how does that grid relate to the 0.1mm grid that we are using as we layout the board in this course?

  • #2
    short answer-> remove manually

    question? are you double clicking? becuase normally you would click left mouse once, it would only set te horizontal trace.. if you right click then it will stop routing mode. and only the single line should stay.. if you double left click you set the 45 degree line bit...

    a bit longer answer
    set grid temporarily to something really smal 0.0001mm of 0.0001 mil (when in routing you can push (G-G) and just put in a x/y grid number (it is one number for bothx/y)
    you can also play around with snapping options..
    there is something called electric grid that is sometimes anoying when it is set too big.. then it will snap to electrical points a.k.a. pads. i believe default is 8mil.. jus tkeep that in any case..

    for me in a practical sence i switch between grids all the time, also since grid is based upon a refenrece point, I also freaquently change my refrerence point to suit my needs. (comes down to me hating to calculate x/y coordinates..

    for the second question:
    place components on a grid, but don't go overboard here... depending on the components one grid or the other might be better for quick placement.
    traces do not need to be on grid..
    when placing polygons a bit more heavier grid makes it easier to close you polygon
    when placing lines on an internal plane its the same as for polygons.. a bigger grid makes it easier..

    hope this helps.


    • #3
      Thank you Tom.

      Hmm ... works in my Altium just fine. There may be an option for this as I remember in old Altium it was doing exactly what you are describing, but in my current AD19, when I am drawing a line from pad which is off the grid, it stays straight. Maybe double check "Snap to Object Hotspots" and "Objects for snapping" options:

      Click image for larger version

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      Click image for larger version

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      2) I do not think you can have everything on grid - in many designs you have mixed mm and mil footprints, so if you really need to stay on grid, you need to create local grids around specific components (but you will be off the global grid anyway). You can have components placed on grid, but other things ... not always. I understand that placing VIAs and drilling on grid may be useful (because it can help with drilling precision), but I do not think tracks are required to be on grid. There may be other things what could be useful have on grid (e.g. openings for stencil) - but as I said that is not always possible as some components are in mils and some are in mm.