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Eagle: via inside a pad, is it possible?

Discussion in 'CAD' started by Dmitri, Dec 6, 2004.

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  1. Dmitri

    Dmitri Guest

    Newbie question, sorry if it's too basic for your guys.
    Trying to save some space/nets/soldering for an SMT board. Some of my
    devices are 1206 and larger (caps), and the size of the pads looks large
    enough to include a via inside. Besides, with the solder all over it
    there's not going to be a difference from the connection stand point. Can
    I just freely move vias around so that they end up INSIDE a device's
    position on a board, specifically its pad?
    Thanks for all your responses!

    --
    Dmitri Abaimov, RCDD
    http://www.cabling-design.com
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  2. Depends.. its not can you put a via inside a pad but how is the board
    getting built... if its automatically pick and place / wave etc.. then no...
    solder will flow down or up the via and tend to stand components upright or
    not solder them down properly. The only time its safe to use via in pad is
    if you use micro vias where the solder can't flow thru the via. Hand
    soldering makes it easier because you can simply add more solder until it
    works.

    Simon
     
  3. Boris Mohar

    Boris Mohar Guest

    If the boar id to be hand soldered than go ahead. If it is to be reflowed
    than you should not do it because the solder paste will be forced through the
    via and it will make a mess on the other side.



    Regards,

    Boris Mohar

    Got Knock? - see:
    Viatrack Printed Circuit Designs http://www3.sympatico.ca/borism/
     
  4. Dmitri

    Dmitri Guest

    Simon, Boris, Thank you for your responses!

    I actually got more insight on the problem than I know what to do with ;-)
    I will be hand-soldering it for now, and will keep your comments in mind
    for the future if I have a chance to do a reflow on one of those boards.

    My question was (I think) simpler: I don't seem to be able to make Eagle
    pickup on the vias placed inside the pads; they just seem to be ignored by
    the router. I'm not sure if it's a principal problem, and vias are just
    not expected to be inside the pads or I'm just not setting the router
    correctly. Honestly, I would not even know which setting would I have to
    play with to make it recognize the vias.

    So, if an Eagle guru happens to read this, I'm still looking for a
    solution ;-)

    Thanks again!

    --
    Dmitri Abaimov, RCDD
    http://www.cabling-design.com
    Cabling Forum, color codes, pinouts and other useful resources for
    premises cabling users and pros
    http://www.cabling-design.com/homecabling
    Residential Cabling Guide
    -------------------------------------


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  5. Hal Murray

    Hal Murray Guest

    My question was (I think) simpler: I don't seem to be able to make Eagle
    I haven't tried it.

    I'd expect it to work if you built a special package that had
    a pad and via touching eachother. The via would be a normal
    through hole via. You would probably have to connect that pin
    on the schematic to both the SMT pad and the via. After that,
    I'd expect the router to notice that they are connected and
    finish things by conecting the via to the right plane or
    routing a trace to it.

    If you are manually adding vias to an existing layout, you
    need to connect the via to that net. (Should give design
    errors if you don't and put it in the middle of a SMT pad.)

    If you don't make that connection, then the new via is part of
    a new net (or something like that) and the router will wire
    it to anything else on that net.
     
  6. David M

    David M Guest

    there should be no problem doing this in Eagle, although it will flag up a
    DRC error. If you are struggling to place it on the pad then the problem is
    likely to be you grid settings. Change to a finer grid size, or use a fine
    alt grid, such that the pad lies on the grid.

    For access to all the Eagle gurus check out the eagle newsgroups, this link
    on the cadsoft website should allow you to set things up.
    http://www.cadsoft.de/forum.htm

    The support groups are fairly active, and most of your future queries will
    have come up at some time before so have a scan over the older meaasges if
    you've got any other queries.

    cheers

    David
     
  7. Dmitri

    Dmitri Guest

    Hi David,

    Thank you for the link. Will definitely take a look at their messages
    archive!

    --
    Dmitri Abaimov, RCDD
    http://www.cabling-design.com
    Cabling Forum, color codes, pinouts and other useful resources for
    premises cabling users and pros
    http://www.cabling-design.com/homecabling
    Residential Cabling Guide
    -------------------------------------







    ##-----------------------------------------------##
    Article posted with Cabling-Design.com Newsgroup Archive
    http://www.cabling-design.com/forums
    no-spam read and post WWW interface to your favorite newsgroup -
    sci.electronics.cad - 3201 messages and counting!
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