The PCB Design Professionals

Power Planes – 11 – Part 1

There are two ways to set up your power planes in Altium either a positive plane or a negative plane. Each have their pros and con’s and I’ll try and touch on that as we explain both.

Firstly we will need to add some extra layers to the design  to do this go to “Design” and then “Layer Stack Manager” or hit “D” then “K” for short. You should get this dialogue box.

I’m going to use a 4 layer design for this example, so I need to add a power plane layer and a normal internal layer for our positive plane. All you have to do is hit the Add Plane button on the right hand side and the add layer button, and you should end up with something like this.

So now you have your four layers one for the negative plane you will also need to define the Net that will exist on that layer. If you double click the Internal Plane layer ((No Net)) you should get a dialogue box that allows you to change the layer name, copper thickness, net name and plane pullback, select your net and click OK. Click OK again to close the Layer Stack Manager.

Negative Planes

OK so we have pretty much set up our negative plane in the layer stack manager but the are a few things you can change.The pull back from the board edge in layer stack manager if required. Also if you would like to split a negative plane layer so that it has more than one net on it this is possible by drawing a line on the plane layer. The thickness of the line determines the clearance between the two planes (pictures Below).

Well thats about it for the basics of negative planes, have a play and see how you get on. I’ve listed a few pros and cons below as promised.

Pros -

• They automatically update
• Are fast to redraw
• Take up minimal system resource.

Cons -

• You cannot draw tracks on a negative plane.
• There is no way to remove dead copper from a negative plane
• They are not as easy to understand as a positive plane.

Part 2 will cover how to draw and manage positive planes keep your eyes peeled. If you have any questions or you would like us to do a tips and tricks on a specific topic, post a comment or email us at blog@blackstick.co.uk