With poly pours on a normal layer, the plane becomes very hard to see through, and so having it at all visible means you can't see other things you need to see, like potential blocking objects on the other side of the board when you're trying to route something. This means if you have a split plane with a few different power domains on it, you can see EXACTLY where the edges of the plane is for the power domain you need, both when placing and moving a component, and when routing component pins down to the plane. For me, the whole magic of plane layers is they are inverted - so they can visually exist in the design and be properly visible without blocking everything else out wherever they go. Basically, I found it fiddly and annoying, and I needed to spend more time routing because of it. I have tried an experiment recently by doing a few of my recent 4 layer (outer tracks, inner planes) designs with poly pours on internal layers instead of plane layers. YES they need a bit of attention, and altium could easily just make them work 100% with a bit of work around the via clearance and plane connect stuff (which I have long given up on them ever doing) but I think the feature is definitely usable for real designs, if you keep in mind there's always a couple of things to manually check, and I don't see it going anywhere. I really like plane layers compared to poly pours on normal layers. Even high-end field solvers/post layout simulators can fail to find issues that can be caused by randomly pouring copper. There are good reasons to do pours ( as in CPW) and the like, but you really need to know what the topology requires and design to that. Also on multilayer designs you now have to deal with asymmetric striplines. It also creates uncontrolled coplanar wave guides, that for most designs are not an issue but as you get into higher speed signals can have a detrimental effect on impedance. When we removed the outer layer copper it passed. congratulations, that's the highest EMI we've ever seen in the lab" was the comment from testers. So we did (even stitched it with vias) and the result was just hideous - ". We did a design for a medical device for a leading medical device supplier where one of the engineers wanted us to do outer layer pours. In fact, at the local test lab, we've found it can actually exacerbate radiation due to things like return paths, coupling, etc. A lot of designers love to add outer layer pours with the idea that it'll somehow aid in EMI emissions and susceptibility. As to top/bot pours again I stay away from that. ![]() In fact, AD17 has some issues with nested split planes causing hangs in being able to save. If I were to do that with internal polys it'd be a nightmare. ![]() Currently working on a design that has 12 layers with 10 being planes with splits. I do a lot of designs with Altium - been an owner since 1995. In fact from what I've seen in AD17 they've added some features for managing planes. I've never read anything concerning the removal of neg planes in AD.
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