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PCB Hole spacing for kinked thru-hole lead

Discussion in 'Circuit Simulation & PCB Design' started by dknguyen, Feb 12, 2018.

  1. dknguyen

    dknguyen Well-Known Member

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    Hey guys:

    When you are designing a footprint for a thru-hole component with pre-bent kinked leads, what hole spacing do you use? Do you use the nominal lead spacing or do you use the spacing of the kink?

    I never gave this much though before because it never really mattered but this is going to be pick-and-placed.
     

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  2. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    The kink is above the board. Do not change the board. Spacing is "A"- lead diameter. (About A)
    upload_2018-2-12_13-16-17.png
     
  3. dknguyen

    dknguyen Well-Known Member

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    Are you sure about that? Because with the kink above the board, that diode sits 1cm above the board which seems pretty high to be.
     
  4. dave miyares

    Dave New Member

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  5. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    Kinks are used to keep hot parts from burning the board. I see then on 2w resistors. Heat transfers to air better when the part is up in the flow.
     
  6. dknguyen

    dknguyen Well-Known Member

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    Hmmm, I'll have to get another part then since that exceeds my board height limit.
     
  7. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    Cut the kinks off. Or use a tool to unbend the wires.
    upload_2018-2-12_15-29-44.png
     
  8. dave miyares

    Dave New Member

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  9. dknguyen

    dknguyen Well-Known Member

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    That won't work for the assembler or the pick and place machine.
     
  10. unclejed613

    unclejed613 Well-Known Member

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    so, if it is too high because of having the board inside a cover, that probably means you aren't going to have much airflow for cooling. if you are running current through that diode that would require it to be up off the board, then restricted airflow is a bad idea. so the question is: how much current is going through the diode? if it's more than half the rated current of the diode, it should be kept off the board. if it's a zener diode, it should definitely be up off the board.
     
  11. dknguyen

    dknguyen Well-Known Member

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    It's being used as a flyback diode so I think it should be okay closer to the board. It's doesn't have clearance not because there is a cover, but because there is an identical PCB stacked on top of it, and another one on top of that, etc.

    EDIT: Oh crap, that reminded me. I forgot to change the order on the part to be the bent but unkinked legs and change the PCB. They have different spacings. Oh well, I guess that's what trial PCB runs are for.
     
    Last edited: Mar 12, 2018
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