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FR-4 Copper Power Layer — Parallax Forums

FR-4 Copper Power Layer

sunblocksunblock Posts: 55
edited 2012-12-27 11:33 in General Discussion
I am polishing up the final traces on a FR-4 PCB board I plan to submit to ExpressPCB. The power layer is a complete copper pour (minus a few vias and DIP pin holes), as is the ground plane. My question is, and there are a number of varying opinions on the subject so I'm throwing this out there, "Is it better to remove as much of the copper pour on the power layer as possible, using the 'Keep Out Of...' exclusion polygons?" Just playing with the design (after I saved it twice), I find can remove almost 90% of the power layer's copper pour. I know the answer will depend on multiple factors, so I guess I'm looking for a general practice set of answers. Thanks and I hope everyone is having a good holday.

Comments

  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-12-26 17:09
    Personally I pour copper ground plane on both sides. And put some vias in strategic locations to stitch them together.
    Duane J
  • frank freedmanfrank freedman Posts: 1,983
    edited 2012-12-26 18:05
    Leave as much copper as you can, easier on the etchant. Uses less, so lasts longer if you do your own etching. Not sure if the fabhouses will give you a break on one-offs, but production may be a different story.
  • Mark_TMark_T Posts: 1,981
    edited 2012-12-27 07:03
    frank freedman wrote: »
    Leave as much copper as you can, easier on the etchant. Uses less, so lasts longer if you do your own etching. Not sure if the fabhouses will give you a break on one-offs, but production may be a different story.

    PCB production is mainly additive I believe, so that doesn't follow: http://infohouse.p2ric.org/ref/28/27484.pdf
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-12-27 07:41
    I order quantities of double sided boards regularly in the 1000 to 5000 quantities. (Actually I have an order for 2000 this afternoon).

    In the big picture of things these quantities are considered small.

    I have discussed these issues, to copper pour or not to pour, a number of times and the consensus is they don't care and don't give me a break either way.

    Things get more interesting with quantities of 100,000 or more.

    Duane J
  • sunblocksunblock Posts: 55
    edited 2012-12-27 09:55
    I am talking about a 4 layer board with copper inner layers (1.25 ounces, 43.75 microns) each. I intend to lesve the entire layer 2 intact (ground plane). Was asking about whether to remove as much of layer 3 (power layer) with exclusion tool to cut down on the amount of electric copper layer, using larger power traces instead of vias from signal layers into the full size power copper layer.
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-12-27 10:10
    I can't think of a reason to not pour copper on the whole layer with the possible exception of areas where RF antennas are located.

    Do you have a special reason not to fill the layer?

    Duane J
  • tonyp12tonyp12 Posts: 1,951
    edited 2012-12-27 10:16
    As I only do hand drawn traces and will fight-to-the-end to get it done on two layers.

    But here is some info about internal power planes:

    Quote: Having discouraged the use of power planes it seems only right that I should give a method for power
    distribution on a ‘good practice’ PCB.I always use the thinnest rather than the thickest tracks I can.

    http://ocw.bib.upct.es/pluginfile.php/8158/mod_resource/content/1/Best_practice_in_circuit_board_design.pdf
  • sunblocksunblock Posts: 55
    edited 2012-12-27 11:33
    Heat is my major concern. Ive read that removal of all power layer copper except traces to power vias aids in performance as well as heat didipation. Since it is fairly easy to do, and the rf ground plane is solid and one layer above... I was wondering what impact if any it might have based on someones experience
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