Polygons inside cutouts inside polygons

Reece R. Pollack wrote:

I'm laying out a board with a ground pour over layer 1. To do this

I've created a polygon that follows the board contour, named it GND,

and set the rank to 6. That works as expected: pins and pads

connected to GND on the schematic automatically connect to the pour

with thermals.

 

In a couple of small areas I want to exclude the ground pour. If I

create a polygon on layer 1 as a cutout I can route nets within it,

but signal polygons placed inside the cutout don't get processed

regardless of rank....................

 

That's correct as described in HELP/POLYGON/Polygon Cutout

 

...............How can I exclude the ground pour while still being able to

create

polygons in the area?

You can make the GND pour have a clear area in the centre by not creating a

simple square polygon around your board but by defining the outer  and inner

edges of the polygon connected by a thin canal. All defined as one polygon.

Think of it as a land locked lake with a small canal to the sea.

When you ratsnest you will see the canal. This you get rid of by moving one

side of it towards the other but if you place the centre of the polygon wire

on top of the other you will get illegal polygon warnings so you have to

stop just short of it.. It is best to make the alternate grid 'finest. so

you can get really close. Your polygon will have wire widths, say 10mil , so

overlap by half this and you will be safe.

HTH

Warren

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How can I exclude the ground pour while still being able to create

polygons in the area?

You seem to want to create some signal polygons inside (or on-top-of)

GND polygon. You can do this by simply drawing the signal polygons over

the same area where the GND polygon already is, BUT assign a lower rank

number to the signal polygon. In this way the signal polygon gets

precedence over the GND polygon. The isolation between GND and signal

polygon is defined either from the design rules or polygon isolate

parameter, whichever is larger.

You had already set the GND polygon rank to 6, so you should have some

idea of the rank option. You can "stack" several polygon layers in this way.

Kim

On 06/27/2013 04:14 AM, Warren Brayshaw wrote:

Reece R. Pollack wrote:

I'm laying out a board with a ground pour over layer 1. To do this

I've created a polygon that follows the board contour, named it GND,

and set the rank to 6. That works as expected: pins and pads

connected to GND on the schematic automatically connect to the pour

with thermals.

 

In a couple of small areas I want to exclude the ground pour. If I

create a polygon on layer 1 as a cutout I can route nets within it,

but signal polygons placed inside the cutout don't get processed

regardless of rank....................

 

 

That's correct as described in HELP/POLYGON/Polygon Cutout

I was just hoping I'd either read it wrong, or there was some trick I

hadn't discovered. sigh

...............How can I exclude the ground pour while still being able to

create

polygons in the area?

 

You can make the GND pour have a clear area in the centre by not creating a

simple square polygon around your board but by defining the outer  and inner

edges of the polygon connected by a thin canal. All defined as one polygon.

Think of it as a land locked lake with a small canal to the sea.

 

When you ratsnest you will see the canal. This you get rid of by moving one

side of it towards the other but if you place the centre of the polygon wire

on top of the other you will get illegal polygon warnings so you have to

stop just short of it.. It is best to make the alternate grid 'finest. so

you can get really close. Your polygon will have wire widths, say 10mil , so

overlap by half this and you will be safe.

Thanks for taking the time to respond. I'd considered something like

this, but it's just too much trouble for what I need.

I think I'll post an idea in the Suggestions group for supporting

subtractive polygons.

-Reece

On 06/27/2013 04:40 AM, KimP wrote:

How can I exclude the ground pour while still being able to create

polygons in the area?

 

You seem to want to create some signal polygons inside (or on-top-of)

GND polygon. You can do this by simply drawing the signal polygons over

the same area where the GND polygon already is, BUT assign a lower rank

number to the signal polygon. In this way the signal polygon gets

precedence over the GND polygon. The isolation between GND and signal

polygon is defined either from the design rules or polygon isolate

parameter, whichever is larger.

 

You had already set the GND polygon rank to 6, so you should have some

idea of the rank option. You can "stack" several polygon layers in this

way.

Normally you'd be right, but in this case I'm working with some GHz

range RF signals and I need a clear area with only the components and

traces I place. Random ground fill would throw off the circuit. I was

hoping to use polygons to avoid having to play games to taper the ends

of traces.

-Reece

Normally you'd be right, but in this case I'm working with some GHz

range RF signals and I need a clear area with only the components and

traces I place. Random ground fill would throw off the circuit. I was

hoping to use polygons to avoid having to play games to taper the ends

of traces.

I don't quite understand how you intend it. You want to clear off an

area from the GND pour and then you want to insert other signal polygons

there? The first can be done with Restrict area or cutout polygon, the

second with overlaying polygons with proper rank order.

If you gave an example of what kind of shapes you are looking for, it

would be easier to help. I use polygon pours all the time, especially in

SMPS circuits (also some RF), and haven't had big problems. Post an

example if you can.

Kim

On 06/27/2013 09:38 AM, KimP wrote:

Normally you'd be right, but in this case I'm working with some GHz

range RF signals and I need a clear area with only the components and

traces I place. Random ground fill would throw off the circuit. I was

hoping to use polygons to avoid having to play games to taper the ends

of traces.

 

I don't quite understand how you intend it. You want to clear off an

area from the GND pour and then you want to insert other signal polygons

there?

Yes, exactly.

The first can be done with Restrict area or cutout polygon, the

second with overlaying polygons with proper rank order.

No, you can't. Cutout polygons don't have a rank order. They cut out

from ALL polygons in that area. You can draw a polygon within a cutout,

but it does not get "processed".

If you gave an example of what kind of shapes you are looking for, it

would be easier to help. I use polygon pours all the time, especially in

SMPS circuits (also some RF), and haven't had big problems. Post an

example if you can.

Ok. I've attached a PNG of a simple test. Let's see if it gets stripped

off by the news server. If it does, here's how I drew it:

1) Draw a square, filled polygon.

2) Draw a cutout within that polygon.

3) Inside the cutout draw another, filled polygon.

4) Click "ratsnest".

Note that the innermost polygon does not get processed.

-Reece

See the attached board

This I think is what you want but still needs some considerations

Name the outer polygon (GND in this example).  Set orphans to off. This

will impact the rest of your board as well but this normally acceptable.

Draw the cutout with restrict wires for that copper layer. The lines can

have zero width. See one of the wires I have set with zero width.

You cannot have any contacts inside the cutout with the same name as GND or

the cutout will be filled. See the left polygon that shows this situation

warrenbrayshaw wrote on Fri, 28 June 2013 09:37

See the attached board

If you need the same GND inside the cutout you should build a link

library device that has GND  on one side and another suedo GND name on

the other. use this to jump the restrict outline

Apologies, I'll change my suggestion, which wasn't very good. Simply draw a

wire the width of the GND trace you wish to take into the cutout area. Name

it GND but terminate it in open space. Then from the suedo GND contact

within the cutout area, bring a trace and terminate it on the end of the

wire. You will get two DRC errors to approve. Simpler all around

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  > Apologies, I'll change my suggestion, which wasn't very good. Simply

draw a

wire the width of the GND trace you wish to take into the cutout area. Name

it GND but terminate it in open space. Then from the suedo GND contact

within the cutout area, bring a trace and terminate it on the end of the

wire. You will get two DRC errors to approve. Simpler all around

2 alternative solutions:

1) Left: With bRestrict wires and boxes limit the area where GND polygon

can pour. There are 2 bRestrict boxes, one inside the other. Outer one

limiting the outer keepout perimeter, and inner the inside area. Note

that there are also bRestrict lines over the GND trace coming into the

inner area. Those are needed to avoid the GND trace (crossing the void

area) from pouring into the "in-between" void area. The trick is to have

no "seed points" inside the void area, from where the polygon pour could

start ("seed points" or polygon pour starting points seem to be vias and

wire joints). All signals named GND, so no DRC errors (except some

restrict warnings where GND and bRestrict overlap).

2) Right: Create 3 overlapping polygons with decreasing ranks. Lower

rank number polygons gets precedence on pour, same rank polygons would

overlap and create shorts (if different signals). To get the YYY polygon

to NOT pour, it has to be isolated from rest of its net. Here I have

put a short wire (also via would work), named also YYY, to create the

net. The YYY polygon doesn't have any indide "seed points", so it won't

pour. The 2nd GND polygon instead, having lower rank number and having

"seed point" inside, will pour. All signals named GND and no DRC errors.

The 1st solution is a bit easier and cleaner, not needing the YYY stub.

The 2nd is a good example how the rank order can be used to create

overlapping but separate polygon areas.

Kim

Attachments:

KimP wrote:

2 alternative solutions:

 

1) Left: With bRestrict wires and boxes limit the area where GND

polygon can pour. There are 2 bRestrict boxes, one inside the other.

Outer one limiting the outer keepout perimeter, and inner the inside

area. Note that there are also bRestrict lines over the GND trace

coming into the inner area. Those are needed to avoid the GND trace

(crossing the void area) from pouring into the "in-between" void

area. The trick is to have no "seed points" inside the void area,

from where the polygon pour could start ("seed points" or polygon

pour starting points seem to be vias and wire joints). All signals

named GND, so no DRC errors (except some restrict warnings where GND

and bRestrict overlap).

 

2) Right: Create 3 overlapping polygons with decreasing ranks. Lower

rank number polygons gets precedence on pour, same rank polygons would

overlap and create shorts (if different signals). To get the YYY

polygon to NOT pour, it has to be isolated from rest of its net.

Here I have put a short wire (also via would work), named also YYY,

to create the net. The YYY polygon doesn't have any indide "seed

points", so it won't pour. The 2nd GND polygon instead, having lower

rank number and having "seed point" inside, will pour. All signals

named GND and no DRC errors.

 

The 1st solution is a bit easier and cleaner, not needing the YYY

stub. The 2nd is a good example how the rank order can be used to

create overlapping but separate polygon areas.

 

Kim

I like the second idea.

While investigating the pros and cons of the two approaches I noticed a

strange behaviour of the vias.( a bug, I suspect).

I thought it may be just my environment but then I noticed it also in the

screen shots you posted. They are not in the board I posted.

Notice the vias have the drill hole hashed. This is not normal.

Move the via and the green via moves but not the hashed circle, which on the

dimension layer. You cannot delete them. Once there, if you copy the via you

copy the bad via. In the end I had 4 of these hashed circles on the

dimension layer plus one wire (Top) of one of my polygons that I could  not

delete or group to delete.

I'm using 6.3.3 (6.4) so this needs to be tested on a later beta to see if

it is currently occurring.

Regards

Warren

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