PCB Design Review - Cramming passives onto a small board

[JamesMerry]

Hey all, I'm trying to figure out my first non-trivial PCB design, and I'm looking for some feedback on where and how to fit bypass caps on a small, 2-layer board.

For context this is an ATSAMD51 dev board that I'd like to make circuit python compatible to run their wonderful synthio library for modular synthesis. I've included a wire terminal for the output to an amp, but other than that, this is mostly a normal dev board. I've tried to keep the form factor feather-compatible, which should let me use an array of pre-made daughter boards.


This is my first dev board with an MCU, and I know bypass caps should be placed as close as possible to the GND and +V pins but I had quite a bit of trouble routing them while still keeping the board reasonably sized and the ground plane intact. This is a 2-layer board because that makes it much easier to prototype with a local PCB manufacturer - Maybe I'd look at more in the future. How much does the exact location matter? Is there a rule of thumb? Is there anything else that could be improved with the routing?

[asmi]

It would really help if you'd show 3D views of the board.

This is my first dev board with an MCU, and I know bypass caps should be placed as close as possible to the GND and +V pins but I had quite a bit of trouble routing them while still keeping the board reasonably sized and the ground plane intact.

The easiest place for bypass caps is often the bottom side of the board directly under the component being bypassed. It's not always the best place for them, but this is what I tend to do in order to achieve tight placement.

This is a 2-layer board because that makes it much easier to prototype with a local PCB manufacturer - Maybe I'd look at more in the future. How much does the exact location matter? Is there a rule of thumb? Is there anything else that could be improved with the routing?

4 layer PCB now cost almost the same as 2 layer ones, but they provide such numerous advantages so that I don't bother with 2 layer boards anymore - except for the simplest breakouts.

[JamesMerry]

Here's a 3D model of the board (except D2 doesn't render for some reason)

I know a four layer would be much easier, thanks for the advice. I've also rerouted it to reduce the number of vias.

[asmi]

Here's a 3D model of the board (except D2 doesn't render for some reason)

It doesn't look crammed at all to me, and it likely work just fine (provided you didn't screw up schematics).

[thm_w]

Looks good to me too.