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Ground pour on the top, supply pour on the bottom. Does this typically increase noise? Is it considered a poor design decision?

It's certainly makes things easier from a routing perspective to pop a via down when you need to supply a pin with power.

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No, it's not a bad design decision, but it's often avoided because it can be a bad design decision sometimes, and many simply choose to use only ground pours on outer layers of the board regardless of the number of layers.

A lot of engineers choose to use only ground pours on outside layers for reasons of impedance (signal integrity), because ground is needed more often than power, and because it's common, many simply assume any visible pour is going to be ground. Many put power planes internal to protect them from damage - an errant screw rattling around inside a case coming into contact with a ground plane is less likely to cause a problem than one coming into contact with a power plane.

It's very convenient to have power pours, though, for some designs, and in two sided through hole designs it does make things easier in some ways. Once you run into a problem, though, you too may adopt a "ground planes or no planes on the outside layers" policy.

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  • \$\begingroup\$ Thanks Adam! After talking to a couple other EE friends, I've decided for this design that I'm going to have a ground plane on the bottom, with minimal jumpers, then connecting SMD pins on the top down to ground through vias, routing power traces as normal, followed by a ground pour. \$\endgroup\$ – Thomas R Jun 14 '15 at 18:16
  • \$\begingroup\$ I'd add that in two-layer PCBs it's difficult to keep a nice unbroken ground plane. Depending on the application, that could produce unintended antennas, ground loops, etc. It's convinient to check for those issues before simply filling any unused copper with GND. \$\endgroup\$ – Guillermo Prandi Jun 15 '15 at 19:10

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