Copper pour isolation around through vias

Mike Vink schrieb:

Hello, I am a newbie with regards to making multilayers, and could use some

help with copper pour.

Copper pour worked fine for me with the 2-layer boards I made up to now.

 

However, I just finished my first 4-layer board with a (12+1516) layer

setup.

My expectation of this was, to get all simple through vias, connecting

whatever traces on each layer they meet.

So far so good.

 

As a last step, I drew polygons for the earth planes and did a copper pour

using Ratsnest.

This presented a problem: most of the vias were cleared by the copper plane,

as set by the isolation distances in the Design Rules.

But some vias now got connected to the ground plane.

 

If you have, f.i., a through via connecting layers 2 and 15, it seems as if

the program isn't aware of it being also present in the remaining outer

layers.

It just treats the via as a hole there, and sees no reason to maintain an

isolation distance between the via and the copper pour.

If I manually route an additional, very short (in fact, just a dot) piece of

trace from such a via onto the offending layers, then copper pour correctly

isolates these layers from the via. Because of time pressure, I scanned this

particular board visually several times and patched all vias so the

isolation was correct.

 

For a complicated board, this is quite a tedious task, and it's easy to

overlook a single via.

Is there something to be done, so the through vias will be recognised over

their full insertion length during copper pour, even if there is no trace

connected to them on that layer?

 

Any help is much appreciated.

 

Best regards,

Mike

Maybe it's only a matter of how the vias are displayed.

The diameter of vias in inner layer is usually smaller than in

the outer layers. See Restring settings in the Design Rules.

It makes sense to set the layer color of layer 18, Vias, to the

background color (DISPLAY menu, Change, Color) if you are working

with vias that have different lengths and shapes and diameters.

In doing so it is  possible to recognize  layer affiliation.

HTH

--

Mit freundlichen Gruessen / Best regards

Richard Hammerl

CadSoft Support -- hotline@cadsoft.de

FAQ: http://www.cadsoft.de/faq.htm

"Richard Hammerl" <ric@cadsoft.de> wrote in message

news:ges6d5$ujv$1@cheetah.cadsoft.de...

snip

 

Maybe it's only a matter of how the vias are displayed.

The diameter of vias in inner layer is usually smaller than in

the outer layers. See Restring settings in the Design Rules.

It makes sense to set the layer color of layer 18, Vias, to the

background color (DISPLAY menu, Change, Color) if you are working

with vias that have different lengths and shapes and diameters.

In doing so it is  possible to recognize  layer affiliation.

 

HTH

 

--

Mit freundlichen Gruessen / Best regards

Richard Hammerl

CadSoft Support -- hotline@cadsoft.de

FAQ: http://www.cadsoft.de/faq.htm

Hello Richard, thanks for your reply.

Just to make sure, I changed the via color as you suggested, but it is not

simply a matter of display.

In fact, first time the problem came to my attention, was when the board

house called me to ask what was going on here.

All the vias mechanically are (or should be, to my understanding) full

length, top to bottom, due to the (12+1516) layer setup.

Electrically, they are only connected to by traces on the layers that need

them.

As an example, I am now looking at a via connecting traces at layers 1 and

2.

Layers 1 and 2 show a correct copper pour with isolation around the via and

its connecting traces.

In layer 15 it is cleared by the copper pour, because there are signal

traces around the via, preventing the copper pour from reaching it.

But in the bottom layer, the copper pour reaches the via and connects to it.

This is also reflected in the Gerber plot of the bottom layer.

When I route a small dummy trace on the bottom layer, connected to the via,

and not larger than the via restring, the via is recognised and the copper

pour isolates from it.

Best regards,

Mike

Mike Vink schrieb:

"Richard Hammerl" <ric@cadsoft.de> wrote in message

news:ges6d5$ujv$1@cheetah.cadsoft.de...

snip

Maybe it's only a matter of how the vias are displayed.

The diameter of vias in inner layer is usually smaller than in

the outer layers. See Restring settings in the Design Rules.

It makes sense to set the layer color of layer 18, Vias, to the

background color (DISPLAY menu, Change, Color) if you are working

with vias that have different lengths and shapes and diameters.

In doing so it is  possible to recognize  layer affiliation.

 

HTH

 

--

Mit freundlichen Gruessen / Best regards

Richard Hammerl

CadSoft Support -- hotline@cadsoft.de

FAQ: http://www.cadsoft.de/faq.htm

 

Hello Richard, thanks for your reply.

 

Just to make sure, I changed the via color as you suggested, but it is not

simply a matter of display.

In fact, first time the problem came to my attention, was when the board

house called me to ask what was going on here.

 

All the vias mechanically are (or should be, to my understanding) full

length, top to bottom, due to the (12+1516) layer setup.

Electrically, they are only connected to by traces on the layers that need

them.

 

As an example, I am now looking at a via connecting traces at layers 1 and

2.

Layers 1 and 2 show a correct copper pour with isolation around the via and

its connecting traces.

In layer 15 it is cleared by the copper pour, because there are signal

traces around the via, preventing the copper pour from reaching it.

But in the bottom layer, the copper pour reaches the via and connects to it.

 

This is also reflected in the Gerber plot of the bottom layer.

 

When I route a small dummy trace on the bottom layer, connected to the via,

and not larger than the via restring, the via is recognised and the copper

pour isolates from it.

 

Best regards,

Mike

 

 

Could you send me the board file? So I could check it.

--

Mit freundlichen Gruessen / Best regards

Richard Hammerl

CadSoft Support -- hotline@cadsoft.de

FAQ: http://www.cadsoft.de/faq.htm

snip

 

Could you send me the board file? So I could check it.

 

 

--

Mit freundlichen Gruessen / Best regards

Richard Hammerl

CadSoft Support -- hotline@cadsoft.de

FAQ: http://www.cadsoft.de/faq.htm

Hi Richard,

After another evening of brain-bashing, I think I found the problem.

When I started routing this board, I found the layer setup notation quite

confusing and fooled around a lot with it.

Time was pressing for the project, so I chose to start doing the layout and

learn about layer setup as I went.

The board was routed initially with the setup being ((12)+(1516)), which

also allowed blind vias in layers 1-2 and 15-16.

After the routing, I performed a DRC with these same rules, which of course

gave no errors on the vias.

The copper pour was done with a separate DRC because I liked to have greater

isolation distances in the ground planes, thereby eliminating some fine hair

traces and needle points in the ground planes. This DRC ignored the

accidentally produced layer 1-2 vias when pouring copper on the bottom

layer.

Only after the feedback from the board house, earlier this week, I realised

that (12+1516) would result in all the vias being through vias, as I

wanted from the beginning.

Tonight, I performed a DRC with the new layer setup and voila, the offending

vias were reported as in violation with the DRC.

All of them were layer 1-2 vias, and after I changed them to 1-16, they were

compliant with the DRC, AND the copper pour isolation was correct.

So, another embarrasing beginners error combined with RTFM, although I tried

the latter and really found it hard to understand at the time.

With hindsight, all is simple.

Thanks for your patience, sometimes it helps to just have a listening ear,

and force yourself to retrace your steps once more.

Maybe others will not make the same mistakes as I did after reading this.

Best regards,

Mike