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Copper Pour Around Vias [message #169333] Fri, 10 February 2017 04:20 Go to next message
T H
Messages: 4
Registered: January 2017
Junior Member
I'm trying to perform a copper pour around a via but it appears to be acting oddly.
[pastedImage_1.png]
I would expect the copper pour to wrap around the via, making a circle with a clearance set by my DRC options.

This becomes a bigger problem when getting a power pour under a BGA with vias; the hexagon shapes waste space.
[pastedImage_9.png]

Does anybody know why it is creating a hexagon shape instead? I have tried adjusting my DRC, changing width of poly, and some other options, but I haven't had any luck.

Any suggestions would be greatly appreciated!

Thanks!

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Re: Copper Pour Around Vias [message #169335 is a reply to message #169333] Fri, 10 February 2017 10:26 Go to previous messageGo to next message
rachaelp
Messages: 551
Registered: March 2015
Location: UK
Senior Member
I think it's just a simplification made due to the way EAGLE currently draws planes, i.e. they are made up of lines of a set thickness. I guess when the via gets reduced below a certain size they think it's acceptable to just make it an octagon instead. I'm not sure why they do this as they calculate the correct circle in the plane when the via becomes larger.

I've not actually had this cause me any issues though. Can you give a screenshot of a situation where this is causing wasted space to show the issue? Hopefully then when the support guys from Autodesk see it they'll be able raise it with the developers.

Best Regards,

Rachael

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Re: Copper Pour Around Vias [message #169336 is a reply to message #169333] Fri, 10 February 2017 13:28 Go to previous messageGo to next message
geralds
Messages: 216
Registered: February 2014
Senior Member
Hi,
It seems that something happens in the layers, e.g. keepout, restrict, 1-16; something invisible that makes this shape.
Cadsoft liked all in octagonal shapes. Your image shows octagonal shapes, not hexagonal.;)

[led-bat.png]
I've changed the pad shape of the resistor for you to round (it comes from the standard rcl.lbr with octagon shape)
Thus, the roundness of the copper pour is also "correct" calculated as almost rounded.
Almost rounded because the calculator draws lines beside lines on grid or off grid. Then it can be happening of rounding errors.
/ This picture has some small spikes. This is because the image is a png file, a compressed image.

Regards,
Gerald
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Re: Copper Pour Around Vias [message #169338 is a reply to message #169333] Fri, 10 February 2017 17:18 Go to previous messageGo to next message
Jorge Garcia
Messages: 1291
Registered: April 2010
Senior Member
On 2/9/2017 11:20 PM, therrm266 wrote:
> I'm trying to perform a copper pour around a via but it appears to be acting oddly.
> [pastedImage_1.png]
> I would expect the copper pour to wrap around the via, making a circle with a clearance set by my DRC options.
>
> This becomes a bigger problem when getting a power pour under a BGA with vias; the hexagon shapes waste space.
> [pastedImage_9.png]
>
> Does anybody know why it is creating a hexagon shape instead? I have tried adjusting my DRC, changing width of poly, and some other options, but I haven't had any luck.
>
> Any suggestions would be greatly appreciated!
>
> Thanks!
>
> --
> To view any images and attachments in this post, visit:
> https://www.element14.com/community/message/215607
>

Hello Therm,

I hope you're doing well. I've seen this before, its not a bug there is
usually an issue with the width of the polygon, try using a lower width
and see if that gives you shape closer to a circle.

As has already been mentioned, polygons are drawn with a bunch of
straight line segments so if the width is large relative to the via size
you may get a hexagon.

Please let me know if you continue to run into problems.

Best Regards,
Jorge Garcia

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Re: Copper Pour Around Vias [message #169340 is a reply to message #169338] Fri, 10 February 2017 17:33 Go to previous messageGo to next message
rachaelp
Messages: 551
Registered: March 2015
Location: UK
Senior Member
Hi Jorge,

When the vias get really small it does this even with the finest width setting. I get the impression that the OP's issue is with really small stuff as he's referring to vias under a BGA so the issue is almost certainly there in that situation. I've done a few tests this afternoon and can easily get it to do this with very small vias.

Best Regards,

Rachael

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Re: Copper Pour Around Vias [message #169345 is a reply to message #169340] Fri, 10 February 2017 22:37 Go to previous messageGo to next message
geralds
Messages: 216
Registered: February 2014
Senior Member
Hi,

yes, that can be. It is absolute possible that he have problems with size.
As what i seem to know the basic shape is an octagon, then a round, then square shape.
Octagon because many years was discussed about octagon or round.
So Cadsoft defined octagon is nearest to the round and better for PCB fabricating.
So what i think what i remember, it was many years in the past. Is it so?

Regards,
Gerald

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Re: Copper Pour Around Vias [message #169346 is a reply to message #169338] Fri, 10 February 2017 22:46 Go to previous messageGo to next message
geralds
Messages: 216
Registered: February 2014
Senior Member
Hi Jorge,


Hm, how do I get hexagon? Not Octagon? - because the computer makes the basic shape in octagon, or not?
An octagon is closer to the round shape than a hexagon, right?
Is this true that there was a discussion about round or octagon? I think I can remember it?!?

Regards,
Gerald
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Re: Copper Pour Around Vias [message #169348 is a reply to message #169333] Fri, 10 February 2017 23:32 Go to previous messageGo to next message
T H
Messages: 4
Registered: January 2017
Junior Member
Thanks for all the responses!

Firstly I misspoke, they are octagons, not hexagons. With that being said, here is a some more detail about what is going on:

* The vias are 18/8, and I might use 16/8 vias.
* The width of the poly is set to 1 mil. I can adjust the poly to anything and it didn't make a difference.
* Since these are vias, I can't adjust them as easily as I could with a part in the library.

I know it might look minor, but in the case when you have an FPGA that can pull close to 10 Amps any amount of copper helps. The red sections in the image below show the areas that I'm missing because Eagle is pouring the copper as an octagon instead of a circle.  Each one of those marks is roughly a mil, and when the opening between the vias is only approximately 6 mils, that is two mils I'm missing between them. Proportionally that is quite a bit.

[pastedImage_3.png]

Again, thank you all for the responses! Hopefully we can figure out a solution.

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Re: Copper Pour Around Vias [message #169401 is a reply to message #169348] Tue, 14 February 2017 23:06 Go to previous message
Jorge_Garcia
Messages: 27
Registered: May 2010
Junior Member
Hello Therrm266,

Sorry for taking so long to reply. Because of the diameter of your vias the octagon shape in unavoidable. See the attached image which illustrates why this is the case. I think this will help clarify the issue for all involved.

[Explanation of octagonal isolations on small vias.png]

Let me know if there's anything else I can do for you.

Best Regards,
Jorge Garcia
Autodesk Support

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