I've looked around for the answer to this question, so I'll only ask the new questions.
I am designing a PC board that has some need for circuits carrying 2 amps and some that are very low power micro-controller (micro-amp) circuits.
I want to use a 4 layer circuit board. The board house I want to use supplies boards with 1oz copper on the top and bottom layers and 1/2oz copper on the inner layers.
My board has a lot of surface mount components, and a small amount of through hole components.
There are DC-DC buck and boost converters on the board, operating around 1 - 2 Mhz (using shielded inductors). There is a microcontroller running a 20mhz crystal as well as a 32.768khz crystal and a USB connector. That's about as fast as my circuit gets.
I am mounting my board into a grounded cast aluminum box to avoid noise.
I see a lot of texts recommending me to use my top layer for power buses and the bottom layer for ground. They say to use the inner two layers for signal routing and low current needs.
I am guessing that is to also provide some noise suppression for the faster circuity in the inner layers.
Because my board and components are fairly dense, (1000+ pins in DipTrace in 4 x 3 inch board) and because they are mostly surface mount components, my question is that I'm finding it easier (and my plan) to route small signal traces on the top layer layer, high speed signal traces on the 3rd (from the top) layer, and use the 2nd layer for Power and the bottom one for ground. I have no high current ground circuits. All of the high current circuits I have are Power circuits.
Is doing this OK or will I run into gotchas (like needing to make sure the traces on the power circuits are double wide because the 1/2oz copper)
And would it be smarter to use the 2nd layer for ground and the bottom (1oz copper) for power? I don't think I need the shielding of the ground being on the bottom since my entire board will be going into the metallic enclosure which will also be ground.