Slots in planes - how? [Protel]

[DTJ]

I'm trying to put a 20mil slot through all layers on a 4 layer board using Protel 99SE.

This is not a physically milled / routed slot, just an "electrical" slot in the copper on all layers 20mil wide and say 50mm deep/long.

Top layer is signal tracks + ground pour.
1st inner layer is gnd.
2nd inner layer is pwr.
Bottom layer is signal + ground pour.


A keep out line wont work as it only applies to the top/bottom layers.

I looked at placing a spit poly plane where the slot needs to go but it needs a net & introduces a floating strip of Cu.


Silly question - how do I do it?

Cheers.

[jmarkwolf]

If I understand your question properly, you need a "slot shaped" void in your plane layers.

Do this simply by placing a track of the desired width, length and location on your plane layer.

Since the plane layers are ultimately a "reverse" image relative to the signal layers, any track (or other entity) on the plane layers will become a "void" in the copper of the plane layer.

[free_electron]

draw a line on the keepout layer in that area. set the line width to 1 mil and write a rule to stay away the desired amount of space.

[DTJ]

Thanks for the replies guys.

jmark - I can see that working but won't it leave a floating unconnected track?


free_electron - will a line on the keepout layer work? Doesn't the keepout layer only apply to tracks and components on the outer (top and bottom) layers?

[langwadt]

If I understand your question properly, you need a "slot shaped" void in your plane layers.

Do this simply by placing a track of the desired width, length and location on your plane layer.

Since the plane layers are ultimately a "reverse" image relative to the signal layers, any track (or other entity) on the plane layers will become a "void" in the copper of the plane layer.

in the old days planes were basically just a reversed image of the pads, does anyone still do planes in reverse?

These days I don't see any reason to not treat all layers as signal layers, some of them just being mostly flood filled
what you draw is what you get

[DTJ]

langwadt - yeah I'd thought about that approach. You've given me some confidence.

As it is the inner layers are all set up as a single net (gnd or pwr). I can see a way to do the slot is to not assign the layer to a net and to just pour a poly with a slot in it and assigned it to the net that I want.
I hope that makes sense!

[free_electron]

Thanks for the replies guys.

jmark - I can see that working but won't it leave a floating unconnected track?


free_electron - will a line on the keepout layer work? Doesn't the keepout layer only apply to tracks and components on the outer (top and bottom) layers?

keepout is keepout. it should work on planes as well

[DTJ]

free electron,

Yep that's what I reckon it should be, so keepout should work.

I've tried the "paint what you want" split plane approach and it works.

I'll try the keepout track approach and see what it looks like with the gerber viewer I've downloaded.

Cheers.

[jmarkwolf]

Thanks for the replies guys.

jmark - I can see that working but won't it leave a floating unconnected track?


free_electron - will a line on the keepout layer work? Doesn't the keepout layer only apply to tracks and components on the outer (top and bottom) layers?

Sorry for the delay in response. Was out of town.

Placing a track on a plane results in a "void" in the Gerber file. No "floating unconnected tracks". Try it, generate a Gerber set and look.