I have designed my first pcb (4 layer) and I have a question about power planes versus power traces. I am using KiCad 7. I have tested the circuitry on a proto-board.

I have a high current section (12-15 V dc @ 3-6 A for 100 - 500 msec), and a lower powerlogic control section (3.3V) - a DAC and ADC controlled by a Raspberry Pi SPI buss (2.4 MHz). I have 2 signal layers, front and back, a ground plane, and a power plane (green). I am debating whether I should (1) use a power plane for the logic chips or just larger traces, and (2) whether I should use a couple of power planes for the high current section or just really fat (5-7 mm) traces.

I have attached two pictures that show the power layer traces in green and potential power planes. Creating a power plane for the logic portion of the design seems to be a good idea. However, the high current section is broken up into so many pieces (e.g. power connector, then a fuse, then a switch, then a relay etc.) that perhaps the fat traces are a better design. What do you think?

 

If you use planes, the tool will use thermal pads for part pins. So you'll have to widen the spokes to accommodate the current. You also have an option of using a thicker copper at a slightly higher cost, but the traces can be thinner for the same current carrying capacity.

 

If you use planes, the tool will use thermal pads for part pins. So you'll have to widen the spokes to accommodate the current. You also have an option of using a thicker copper at a slightly higher cost, but the traces can be thinner for the same current carrying capacity.

Thanks for your comments. I plan to use 1 oz Cu on the inner layers. Do you think I should use a power plane for the digital electronics or not? Same question for the power traces.

 

My boards look like your first picture. I use a combination of planes and traces. I usually turn off the thermals on the power planes to get a better connections. (solid) Soldering and desoldering is harder. I am running 1000A and need a really good connection. I also double up layers. Make a plane and set it to Top and L1. In some cases, I use all four layers for lowest resistance. Looking at the top half of your board you can use 2, 3 or all layers in some places.

I don't know your voltages. If you have power line voltage you should have more spacing. There are ways to have Kicad help with that.

ps
You can have power in a plane or ground in a trace. The electrons don't care what you call the copper.

 

My boards look like your first picture. I use a combination of planes and traces. I usually turn off the thermals on the power planes to get a better connections. (solid) Soldering and desoldering is harder. I am running 1000A and need a really good connection. I also double up layers. Make a plane and set it to Top and L1. In some cases, I use all four layers for lowest resistance. Looking at the top half of your board you can use 2, 3 or all layers in some places.

I don't know your voltages. If you have power line voltage you should have more spacing. There are ways to have Kicad help with that.

ps
You can have power in a plane or ground in a trace. The electrons don't care what you call the copper.

No AC, just 12-15 V dc - from a battery.
I never thought of having 2 power planes joined with vias....a whole new idea! Thanks!