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Break away rails?

Former Member

Could someone provide some tips on how to add "break away rails" to a

PCB?  Is there anything in the Eagle documentation/tutorials that offer

any insight.  I know what they are and have had break away rails added

to may boards that I have worked on, but I have not done this part of

the layout.  The PCB houses call the tabs with holes which attach to the

main board "mouse bites".  This is just done with drilled holes I

assume, but I have no idea of what size drill or how closely to space

them.  If anyone has an example of this in Eagle that they'd be willing

to share I'd be most grateful.

 

Regards,

 

Michael

 

  • Michael Sansom wrote:

    Could someone provide some tips on how to add "break away rails" to a

    PCB?

     

    The board house noramlly wants to add thoose themselves.

     

    Just tell them if there are places you do not want them.

    There are many variants.

    For example they can be made a bit into the board so when they break

    ther eis nothing stickin out past the drawn outer line, bu tin that case

    make room for that construction (leave space close to the border there)

    after discussing with manufacturer.

     

    Or maybe simple bridges in the corners are an option for small boards,

    easy to cut manually.

     

    Bottom line: first ask manufacturer.

     

  • Michael Sansom wrote:

     

    This is just done with drilled holes I assume, but I have no idea of

    what size drill or how closely to space them.

     

    I based my routed breakaways on the recommendations from IPC-SM-782

    figure 3-31.  They specify 5x Ø0.8mm holes at 1.25mm spacing centred

    across the "tab" that is 4.5mm wide.   They recommend a typical spacing

    of 75mm between breakaways.

     

    The actual dimensions of the breakaway might vary with the width of

    router tool used.  I use a Ø2.0 mm router.

     

    If anyone has an example of this in Eagle that they'd be willing to

    share I'd be most grateful.

     

    Some examples attached - one for an edge tab and one for joining two

    sections of pcb.  They have been adequate for me but YMMV: check with

    your assembly people as to what they want.

     

    Regards

    Neil