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 Why does 0603rf_wv_12d have two vias in it? 

Last post Sat, Apr 27 2013 1:58 PM by ScottCad. 4 replies.
Started by TAyres 16 Apr 2013 01:19 AM. Topic has 4 replies and 975 views
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  • Tue, Apr 16 2013 1:19 AM

    • TAyres
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    Why does 0603rf_wv_12d have two vias in it? Reply

    I'm trying to understand this symbol; I've examined SMD pins that are just top layer rectangular pads with an oversized mask; that makes sense. But why does this symbol have two vias on it? Just trying to understand the logic/rationale behind it.

     

    Thanks all! 

    • Post Points: 65
  • Wed, Apr 24 2013 8:22 AM

    • David Yackman
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    Re: Why does 0603rf_wv_12d have two vias in it? Reply

    Not sure...  It's a strange looking symbol.  It was done in an older version of OrCAD than I have, so it doesn't open up normally, anyway.  It doesn't look like the vias connect to anything.  Maybe the vias are used as some sort of alignment hole?  I don't know.  What kind of part is this supposed to fit?  Most of the footprints included in OrCAD aren't identifiable, so I end up drawing my own.

    • Post Points: 5
  • Thu, Apr 25 2013 8:15 AM

    • BuddSw
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    Re: Why does 0603rf_wv_12d have two vias in it? Reply

    That is one strange footprint, but then all 4 of the SMT parts that start with xxxxRF_ are odd.  The vias are connected to the pads with traces.  I am guessing that the the "rf" part of the name is shorthand for REFERENCE.  My take is that the name decodes as a reference version (the rf) of an 0603 with vias (the wv) and the size of the via drill (the 12d). I did check the via and the pad stack calls for a 12 mil drill. I can't imagine trying to use that footprint for anything.  Oh, my other guess is that the rf means it is intended for RF circuits but I find that highly unlikely. Like David, I create my own footprints.  In my case I use an obsolete but still useful MIL-STD for my 2-contact parts.  It takes into account the z-axis dimension to create a solder fillet that is at least 25% of the component height.  As such I have separate footprints for resistors, capacitors, inductors and such.  Using this standard allows for boards that pass severe Navy-level shock and vibration requirements. IPC-7351 appears to be oriented more toward consumer and light industrial markets and that is why I choose not to use it.

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  • Thu, Apr 25 2013 12:29 PM

    • mcatramb91
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    Re: Why does 0603rf_wv_12d have two vias in it? Reply

    In some cases, librarians add fanout (pin escapes) to their library symbols to save time during layout and to have a more consistent component fanout in all locations. 

    My opinion is that the RF stands for Reflow (as the Reflow SMD Pads are sometimes different than the SMD Pads for the Wave solder process) and the WV stands for With Vias. 

    I have worked with several companies that had a very specific naming convention to identify footprints in the library and it is not uncommon to have different footprints based on the soldering process, spec build to IPC, MIL, etc. or different footprints with and without fanout.  It is sometimes recommended to fanout off the side of discrete components (at the heel of the pads) vs fanout out the far edges (at the toe of the pads) as the electrical path to the metallization of the discrete component is closer when you fanout from the side which in turn makes the connection to the internal planes that much shorter.

    My two cents,
    Mike Catrambone

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  • Sat, Apr 27 2013 1:58 PM

    • ScottCad
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    Re: Why does 0603rf_wv_12d have two vias in it? Reply

    Hi Guys, my 50 cents on this one.

    It is an unusal symbol but i believe it was designed for use on a flex circuit.

    0603 Resistor Flex with vias 12mil diameter hole.

    Thanks Scott

    • Post Points: 5
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Started by TAyres at 16 Apr 2013 01:19 AM. Topic has 4 replies.