Best way to make a split power plane?

[Brad Parker]

I have a simple 4 layer design, but it has split power plane with 3
distinct areas.

My initial attempt was to
- define 3 power planes ($+5v, $+3v3, $vddcore)
- make a wide wire (40 mils) surrounding each area in $+5v
- plot all 3 supply layers on top of each other

This made gerbers which looked fine, but it turns out that each layer
fills in the vias for the other layers, which wipes out the thermal
reliefs.

What's the best way to tackle this? I'd rather not draw polygons,
but I guess I could and then prioritize them. Two of the laters are
distinct and one falls in the middle of another.

thanks!

-brad

[Ing. Mike Miller]

Post by Brad Parker
I have a simple 4 layer design, but it has split power plane with 3
distinct areas.
My initial attempt was to
- define 3 power planes ($+5v, $+3v3, $vddcore)
- make a wide wire (40 mils) surrounding each area in $+5v
- plot all 3 supply layers on top of each other
This made gerbers which looked fine, but it turns out that each layer
fills in the vias for the other layers, which wipes out the thermal
reliefs.
What's the best way to tackle this? I'd rather not draw polygons,
but I guess I could and then prioritize them. Two of the laters are
distinct and one falls in the middle of another.
thanks!
-brad

Sorry Brad but IMHO polygons are going to be your best method.

Regards,
Mike.

[Zoltan Dobrovics]

Well, you just answered your own question, that works great for me.

Post by Brad Parker
I have a simple 4 layer design, but it has split power plane with 3
distinct areas.
My initial attempt was to
- define 3 power planes ($+5v, $+3v3, $vddcore)
- make a wide wire (40 mils) surrounding each area in $+5v
- plot all 3 supply layers on top of each other
This made gerbers which looked fine, but it turns out that each layer
fills in the vias for the other layers, which wipes out the thermal
reliefs.
What's the best way to tackle this? I'd rather not draw polygons,
but I guess I could and then prioritize them. Two of the laters are
distinct and one falls in the middle of another.
thanks!
-brad

[Brad Parker]

I wrote a program to remove the "redundant" pads from the gerber.
It basically looks for the thermals and removes pads which plot to the same
address. It's a hack, but it seems to do the right thing.

I think this is easier than using polygons, but since I haven't done it, I
may
be wrong. I will try polygons, but I need to experiment with them first.

When using a polygon for the power plane should you *not* use the $signal
convention? Also, what affect does it have on the CAM - I assume you need
to tell it to plot the various polygon layers to the same file.

Post by Zoltan Dobrovics
Well, you just answered your own question, that works great for me.

Post by Brad Parker
I have a simple 4 layer design, but it has split power plane with 3
distinct areas.
My initial attempt was to
- define 3 power planes ($+5v, $+3v3, $vddcore)
- make a wide wire (40 mils) surrounding each area in $+5v
- plot all 3 supply layers on top of each other
This made gerbers which looked fine, but it turns out that each layer
fills in the vias for the other layers, which wipes out the thermal
reliefs.
What's the best way to tackle this? I'd rather not draw polygons,
but I guess I could and then prioritize them. Two of the laters are
distinct and one falls in the middle of another.
thanks!
-brad

[Paul Romanyszyn]

Post by Brad Parker
I think this is easier than using polygons, but since I haven't done it, I
may
be wrong. I will try polygons, but I need to experiment with them first.

Good idea look up rank and don't set the width too narrow.

Post by Brad Parker
When using a polygon for the power plane should you *not* use the $signal
convention? Also, what affect does it have on the CAM - I assume you need
to tell it to plot the various polygon layers to the same file.

It is possible to use polygons on a two layer board for the power and
grounds without the need for the extra cost of multilayer.
This is a two layer board. Anything over 10 mill is a polygon also thing
that don't look like a trace.

The analog section is in the right upper area. I leave a gap between the
top gnd and bottom gnd above and below and overlap on the lower left
side. On the planes it is best to add several vias to make multiple
connections between top and bottom grounds and power polygons.
Loading Image...

So rename your power plane layers that have $ to remove it. The power
planes I think display what is removed while non power plane layers show
what is copper. I have never used them.
Setup your layers stack in DRC. Once you have a named polygon edit with
split and use move to adjust the location. also miter can be used to
remove extra segments.

Until the next version release of eagle traces are currently modeled
with a octagon tool to speed up calculations but Gerber support only
round tools. Because of that if you use traces over 20 mil and fill
around them the fill will show the clearance from octagon ends of the
trace. So I replace all of my thick traces with polygons. Which as the
advantage of not having to carefully place them since they will auto
clearance during the ratsnest.

Paul R

[Ing. Mike Miller]

Post by Brad Parker
I wrote a program to remove the "redundant" pads from the gerber.
It basically looks for the thermals and removes pads which plot to the same
address. It's a hack, but it seems to do the right thing.
I think this is easier than using polygons, but since I haven't done it, I
may
be wrong. I will try polygons, but I need to experiment with them first.
When using a polygon for the power plane should you *not* use the $signal
convention? Also, what affect does it have on the CAM - I assume you need
to tell it to plot the various polygon layers to the same file.

If you have a single power plane (or ground plane) per layer then use
the $signal convention. For split planes i.e. 2 or more signals on the
same layer then best to use polygons. YOU CAN NOT MIX THE 2 METHODS ON
THE SAME LAYER (sorry for shouting)!

There is no effect on the CAM processing. Anything that shows up as
copper in the design shows up as copper in the files.

Regards,
Mike.

Post by Brad Parker

Post by Zoltan Dobrovics
Well, you just answered your own question, that works great for me.

Post by Brad Parker
I have a simple 4 layer design, but it has split power plane with 3
distinct areas.
My initial attempt was to
- define 3 power planes ($+5v, $+3v3, $vddcore)
- make a wide wire (40 mils) surrounding each area in $+5v
- plot all 3 supply layers on top of each other
This made gerbers which looked fine, but it turns out that each layer
fills in the vias for the other layers, which wipes out the thermal
reliefs.
What's the best way to tackle this? I'd rather not draw polygons,
but I guess I could and then prioritize them. Two of the laters are
distinct and one falls in the middle of another.
thanks!
-brad

[Jim Ashby]

Before you all start yelling at me for posting a repeat answer, please
consider the posting was not just a question of fact, but a request for
validation on the choices presented.

The responses have been good and direct, but not as informative as they
could have been.

So as a repeat answer:
_______________________________________________________________________
OK, I have just got off the phone with the great tech support we have
access to here in the USA for Eagle tools. KUDOS!

I had a problem with no connections to my dual ground plane (Digital and
Analog) from the via's I had places from surface mounted components on
both the TOP and BOTTOM layers.

I had layer 2 = $GND and layer 3 = $VCC setup.

Then I placed two separate polygons on both of these layers covering the
entire board space.

I have just learned that this is not the proper way to do this.

You can either do a ground layer and define in the layer command that it
is a "supply layer" and let the auto-router do the copper pour on this
layer, or you can place polygons on the desired layer and NAME the
polygons the same as the signals you need attached to it.

When I named the layer a "supply layer" and then placed a polygon on the
layer, it removed the "supply layer" copper pour automatic function, so
none of my signals were connected to this layer, because the layer did
not contain the "supply layer" copper. DUH!

The other restriction to using "supply Layers" is that if you need
multiple isolated copper pours on a single layer, then the "supply
Layer" function can not be used, because each layer can not contain more
than one definition "name".

One other point of interest; while I deal with the design stage I find
it easier to set the polygon width to zero. This opens up the ability
to view through the polygon while placing components. Once I am
finished with the layout, I change the polygon width to .012" and this
shows the polygon fill to view the full fill of the polygon.

I needed to post this message just in case it helps someone else.

Thanks to all!

I find this forum a great helper when things get tough, and I get dumb.

Jim Ashby
IDE Solutions, Inc.
_______________________________________________________________________

Post by Ing. Mike Miller

Post by Brad Parker
I wrote a program to remove the "redundant" pads from the gerber.
It basically looks for the thermals and removes pads which plot to the same
address. It's a hack, but it seems to do the right thing.
I think this is easier than using polygons, but since I haven't done
it, I may
be wrong. I will try polygons, but I need to experiment with them first.
When using a polygon for the power plane should you *not* use the $signal
convention? Also, what affect does it have on the CAM - I assume you need
to tell it to plot the various polygon layers to the same file.

If you have a single power plane (or ground plane) per layer then use
the $signal convention. For split planes i.e. 2 or more signals on the
same layer then best to use polygons. YOU CAN NOT MIX THE 2 METHODS ON
THE SAME LAYER (sorry for shouting)!
There is no effect on the CAM processing. Anything that shows up as
copper in the design shows up as copper in the files.
Regards,
Mike.

Post by Brad Parker

Post by Zoltan Dobrovics
Well, you just answered your own question, that works great for me.

Post by Brad Parker
I have a simple 4 layer design, but it has split power plane with 3
distinct areas.
My initial attempt was to
- define 3 power planes ($+5v, $+3v3, $vddcore)
- make a wide wire (40 mils) surrounding each area in $+5v
- plot all 3 supply layers on top of each other
This made gerbers which looked fine, but it turns out that each
layer fills in the vias for the other layers, which wipes out the
thermal
reliefs.
What's the best way to tackle this? I'd rather not draw polygons,
but I guess I could and then prioritize them. Two of the laters are
distinct and one falls in the middle of another.
thanks!
-brad

[Lynn Graves]

Post by Jim Ashby
I needed to post this message just in case it helps someone else.

Sure helped me! Of course that may not be a compliment, since anything
seems to help me lately (grin). I have been experimenting with polygons for
the past few days, and will now have to try "supply layers".

The strange thing is that I seemed to understand everything you said about
polygons! Now there's a first, a post that I understand!

Post by Jim Ashby
Jim Ashby
IDE Solutions, Inc.
_______________________________________________________________________

Post by Ing. Mike Miller

Post by Brad Parker
I wrote a program to remove the "redundant" pads from the gerber.
It basically looks for the thermals and removes pads which plot to the same
address. It's a hack, but it seems to do the right thing.
I think this is easier than using polygons, but since I haven't done
it, I may
be wrong. I will try polygons, but I need to experiment with them
first. When using a polygon for the power plane should you *not* use the
$signal convention? Also, what affect does it have on the CAM - I
assume you need
to tell it to plot the various polygon layers to the same file.

If you have a single power plane (or ground plane) per layer then use
the $signal convention. For split planes i.e. 2 or more signals on
the same layer then best to use polygons. YOU CAN NOT MIX THE 2
METHODS ON THE SAME LAYER (sorry for shouting)!
There is no effect on the CAM processing. Anything that shows up as
copper in the design shows up as copper in the files.
Regards,
Mike.

Post by Brad Parker

Post by Zoltan Dobrovics
Well, you just answered your own question, that works great for me.

Post by Brad Parker
I have a simple 4 layer design, but it has split power plane with
3 distinct areas.
My initial attempt was to
- define 3 power planes ($+5v, $+3v3, $vddcore)
- make a wide wire (40 mils) surrounding each area in $+5v
- plot all 3 supply layers on top of each other
This made gerbers which looked fine, but it turns out that each
layer fills in the vias for the other layers, which wipes out the
thermal
reliefs.
What's the best way to tackle this? I'd rather not draw polygons,
but I guess I could and then prioritize them. Two of the laters
are distinct and one falls in the middle of another.
thanks!
-brad