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 Trim A Pad? 

Last post Fri, May 3 2013 1:17 PM by David Yackman. 11 replies.
Started by David Yackman 30 Apr 2013 11:18 AM. Topic has 11 replies and 1257 views
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  • Tue, Apr 30 2013 11:18 AM

    • David Yackman
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    Trim A Pad? Reply
    I have a PCB that must meet some odd mechanical requirements.  The PCB has one header and 3 spring-loaded pins.  Due to where these pins must be in relation to the board outline, one of the pin's footprint will overhang the edge of the board slightly.  I need to trim just a bit off the edge of the pin, but I haven't figured out how to do this.  There's no trim or cut feature that I could find that would allow me to trim the edge off of just one pad.  Can anybody tell me how to do this?
    • Post Points: 20
  • Tue, Apr 30 2013 11:33 AM

    • Rik Lee
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    Re: Trim A Pad? Reply

     David,

     Look at the editpad boundary command (Tools > Pad > Boundary)

    • Post Points: 20
  • Tue, Apr 30 2013 1:02 PM

    • David Yackman
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    Re: Trim A Pad? Reply
    Rik, I didn't find that option.  I guess I should've mentioned that I'm using OrCAD PCB Designer Professional 16.6... 
    • Post Points: 5
  • Tue, Apr 30 2013 1:11 PM

    • David Yackman
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    Re: Trim A Pad? Reply
    I should also add that if I search the "documentation" I find a page describing how to use this feature, but it doesn't say which program I should use it in.  I have no option even close to what's shown in the help document.
    • Post Points: 20
  • Wed, May 1 2013 2:37 AM

    • steve
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    Re: Trim A Pad? Reply

    The Pad boundary option is only avaliable in the Allegro license options. It's not there in OrCAD PCB but what you can do is use Tools - Padstack - Modify Design Padstack, then select the Pad. In the Options fold out menu make sure you select Instance so that this edit is only for this pad only (it will rename the padname to padname_1) then click on Edit and change the pad size accordingly in Pad Designer. Once complete use File - Update to Design and Exit and the pad will be replaced.

    • Post Points: 20
  • Wed, May 1 2013 4:37 AM

    • David Yackman
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    Re: Trim A Pad? Reply
    Oh, that SUCKS! So, unless I'm missing something, the only way I can trim away the edge of a pad is to first draw a custom shape, import that shape into Pad Designer, add the through hole, create a new symbol, and hope it fits.  I'll have to do this three times.  It seems to me that there would be a "trim" feature kind of like in AutoCAD, but I guess not.  Maybe it's easier just to buy a Gerber editor.  Does anybody have any suggestions about which Gerber editor is the easiest to use?
    • Post Points: 5
  • Wed, May 1 2013 12:18 PM

    • David Yackman
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    Re: Trim A Pad? Reply
    OK.  Update.  I purchased a Gerber editor tool online for $95.  I can now trim pads. 
    • Post Points: 20
  • Thu, May 2 2013 12:59 PM

    • BuddSw
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    Re: Trim A Pad? Reply

    David, a word of caution. If you do not create a padstack that meets your requirements, the next time Gerbers are generated you will have to hand-fix the problem again. When I was in charge of other designers making changes with a Gerber editor was expressly forbiden for this very reason. Your solution works for the short time, I agree, but for the long haul it is a chancy choice.

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  • Fri, May 3 2013 12:29 PM

    • David Yackman
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    Re: Trim A Pad? Reply
    BuddSw, I agree with you.  This is the first time I've ever used a Gerber editor.  For years, the only Gerber tools I had were viewers, just to verify the files before I sent them off for fabrication.  However, there really was no other practical way to do what I needed done.  I was forced to make a PCB that goes totally against the grain of what passes for a good, manufacturable PCB to fit some odd mechanical requirements.  I could've conceivably drawn the pin somehow as a shape and then made it a pad stack, but I needed the shape to be trimmed very specifically in relation to the surrounding plane and the board outline. It would've been great to be able to just trim the pad in the layout screen rather than messing around with a Gerber editor. Since this is the first time I've done this, I'm making a few prototype boards that I will hand populate just to make sure everything worked out fine.  I don't see myself using the editor frequently; after all, I've done without one so far. Good thing it only costs $95!
    • Post Points: 20
  • Fri, May 3 2013 12:42 PM

    • BuddSw
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    Re: Trim A Pad? Reply

    I'm curious as to what the pad shape is that you had to trim? Not terribly important but curious.

    I've spent a reasonable part of the last 18 years of my career dealing with power conversion electronics (150kW to 4MW) really high power stuff.  Because of the nature of the beast I too have had to deal with many oddball shapes for boards that had nothing to do with reasonable placement or signal flow.  You have my sympathies.

    • Post Points: 35
  • Fri, May 3 2013 1:13 PM

    • David Yackman
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    Re: Trim A Pad? Reply
    Not sure how to post an image - if I can figure it out, I'll show you.
    • Post Points: 5
  • Fri, May 3 2013 1:17 PM

    • David Yackman
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    Re: Trim A Pad? Reply
    The three pins to the left are the problem.  The center one is normal.  The two on the top and bottom had to be trimmed.
    • Post Points: 5
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Started by David Yackman at 30 Apr 2013 11:18 AM. Topic has 11 replies.