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Any significance to the shape of the solder pads on a PCB?

Discussion in 'Electronic Repair' started by Nelson, Aug 21, 2013.

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  1. Nelson

    Nelson Guest

    I am trying to create a schematic from a PCB and I notice each
    component has one square solder pad hole and one circular one. Is
    there any significance to that?
     
  2. "Nelson" wrote in message
    Perhaps it indicates the polarity of diodes, LEDs, etc.
     
  3. Paul Drahn

    Paul Drahn Guest

    100% correct!

    Paul
     
  4. Nelson

    Nelson Guest

    But all the resistors are that way too :) The board appears to have a
    plane sandwiched between the top and bottom. I'm guessing it is either
    a ground plane or a V+ plane. I thought maybe one or the other
    indicated a plated through hole that connected to the mid plane.
     
  5. Paul Drahn

    Paul Drahn Guest

    I thought you were referring to the silk screen art work. Are you saying
    you took all the components off the board and sucked the solder out of
    the holes so you can now see that some holes were drilled and some were
    punched with a square punch?

    A properly soldered board will not show any hole if they are
    plated-through holes.

    Paul
     
  6. Guest

    Back when I worked with Tango (jurassic era) the pins had a name to match up with the pads in PCB. For non-polar components like resistors the pads were A and B. All the through hole footprints had 1 square terminal. The schematic component had the same name for the pins to match up with the pad name. Failing name matching would cause a net list error and you want NO net errors if you expect it to work.

     
  7. "Paul Drahn" wrote in message
    He's referring to the shape of the metal pad, not the hole.
     
  8. Nelson

    Nelson Guest

    Well, maybe not all the resistors, but quite a few of them. Here's a
    photo:

    http://www.deejr.net/pbp/2013/08/21/PowerBoardFront.jpg
     
  9. Nelson

    Nelson Guest

    Thanks! I'm having a hard time visualizing this, however. I have
    researched "thermal relief" which is what I think you are referring to
    but I can't find any discussion of square pads contacting only at the
    corners. In particular, in this case, the ground plane or "copper
    flow" appears to be an interior layer. I can't visualize how the
    through holes connect to this or pass through without connecting.

    Here is an image of the back of the board showing the embedded ground
    plane:

    http://www.deejr.net/pbp/2013/08/22/PowerBoardBack.jpg

    As you can see there are quite a few square pads which don't appear to
    connect to the ground plane.
     
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