PCB Layouts- Components over tracks

Discussion in 'Homework Help' started by Adille, Mar 10, 2014.

  1. Adille

    Thread Starter New Member

    Mar 10, 2014
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    Hi, this will probably be one of the foolish questions but I am new into buisness :D (first year student) and generaly I am working on a PCB layout and I am wondering can I have componets going over the tracks, I am asking will this work in practice. More clearly I am talking about having didoes over tracks acting as sort of bridges.
     
  2. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    If I am understanding you correctly, yes--that is perfectly fine. Just make sure you allow enough clearance between the traces and on either side near the diode pads. If you aren't sure how much clearance you need, check with your boardhouse to see how much they require.

    Good luck!
    Regards,
    Matt

    P.S. Welcome to the forum! :)
     
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  3. Adille

    Thread Starter New Member

    Mar 10, 2014
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    Right, Thanks a lot for that,
    My lecturer will surely check if I am correct tommorow,
    but I rather making an attempt at it and fixing it, if its wrong
    rather than coming in empty handed and finding out my thinking was right.

    Thanks just found the forum but from a quick glance I can see, it
    might be very helpful in future.
     
  4. #12

    Expert

    Nov 30, 2010
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    Jumping traces with a leaded component is a time honored tradition. It solves many difficulties in layout. Of course this requires a hole and solder pad for each end. Strangely bulky compared to surface mount components, but worth the used up real estate in most cases, especially if it avoids adding another layer to the PC board.
     
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  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Another long standing tradition is jumper wires: no component, just a wire to jump over other connections. Mostly used in "single sided" boards here traces only exist on one side of the board. May need to use insulated wire, or just a stiff wire held off the board.

    One day you will also learn about the zero ohm resistor. It is a small device made with the same material as standard resistors, except the terminal on one side went straight thru to become the terminal on the other side. They even had color code bands, except these just had a single black band.

    I am not sure it is true that they were invented to meet certain military specification projects where jumper wires were forbidden, but components were somehow allowed.

    No one could argue a zero ohm resistor was "just a jumper wire" and they passed any and all qualification inspections.
     
  6. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    It is important to note, however, that jumper wires are generally avoided whenever possible and should only be used in worst-case scenarios. For most simple boards you should be able to route the traces in such a way so as to not require jumper wires.
     
  7. JohnInTX

    Moderator

    Jun 26, 2012
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    My understanding is that zero ohm resistors allowed jumpers to be sequenced on tape and reel for auto insertion. At least that's how I used them back in the day. Agreed ErnieM, running traces under components-as-jumpers is an acquired skill and ever so useful.
     
  8. crutschow

    Expert

    Mar 14, 2008
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    Unless the surface mount components are very small you can also run traces under them (within the minimum trace-width and spacing limits of course) as I've done many times myself. Doesn't need to be limited to through-hole components.
     
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  9. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Agreed, I have often had to run two or three traces underneath surface mount components, though those components were fairly large. In general, as long as you're careful about your clearance, you can usually fit at least one trace under a SMD.
     
  10. MrChips

    Moderator

    Oct 2, 2009
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    Shucks, not only can you run traces under DIP packages, you may even be able to squeeze one or two tracks in between IC pins. I usually don't squeeze more than one trace in between 0.1" pitch pins but I haven't done that in a long time since all my layouts now are using SMD. I would on a rare occasion slip a track under an 0805 resistor or capacitor but that's as far as I will push it.
     
  11. CapeCAD

    New Member

    Jul 16, 2011
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    With 5 mil width/space: Two traces under an 0603 component or 1 trace under an 0402 component are common.
     
  12. magnet18

    Senior Member

    Dec 22, 2010
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    zero ohms SMD's are very common if you change a matured design, they let you remove parts and tune things without changing traces, and it's easier to use the same form factor (also probably true with through hole parts)

    I know when you have a 16 layer all SMD board meeting military specs, you DONT want to change the traces... ever...

     
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