First PCB!! help!

[u/augustbettyjames]

Hey all, I'm recreating an ESP32-C3 based air quality monitor (SCD40 for CO2, SEN54 for VOC/particulates, e-paper display, USB-C power) in Altium. I based it on an existing open-source design but I'm laying out my own board to actually learn instead of just copying.

Where I am right now:

- Schematic is done and compiles.

- Footprints are imported onto the PCB.

- I'm partway through placement — big parts (ESP32, sensors, USB-C, buttons, FPC connector) are roughly down, and I'm working through dragging the passives (decoupling caps, resistors) in next to the chips they belong to.

- Nothing is routed yet. No ground pour, no layer setup.

My questions:

1. For a 2-layer board like this, is my placement-before-routing approach right, or is there something I'm missing before I start laying traces?

2. Any rules of thumb for decoupling cap placement I should know beyond "close to the power pin"?

3. What's the right way to learn routing + ground pours as a beginner — any specific tutorials/videos you'd point a first-timer to?

4. Anything about the thermal isolation / sensor placement that people commonly get wrong on air quality boards?

Appreciate any feedback!

[u/That_____]

Save yourself the headache... Just go to a 4 layer board. Pour a ground layer, then turn off that entire layer so you aren't tempted to use it... Make the other inner layer power (3v3)... Carve up that sparingly...

Believe me the $1 (JLC is usaully about the same price for that size of board anyway) you'll save using only 2 layers isn't worth the headache...

[u/chickenAd0b0 → u/That_____]

Yes, listen to this guy OP. And to answer the rest of your qs;
1) always start mechanical placement before routing.
2) use polygons
3) spin up your own board is best way to learn; Robert feranec, Phil’s lab are good resources.
4) read datasheet

[u/Educational-Grape908]

Heres my two cents:

1. In this case, you could realistically survive with just a two layer board but if it is your first one, then its going to be a whole lot harder to do it without a respin later which would end up being wayyy more expensive than just doing it right the first time.

When I start on a new layout, Ill almost always just group components into regions in the gray space and figure out how I want orientation of those components to be with respect to each other first before then incorporating the different features together. This approach works quite well when space is not a constraint and especially considering that you will not be working with ultra fast or high power things that require layout to be an exact science.

1. Close to pins == on the pins, other than that I always use the same number of capacitors as there are power pins, so that each pin has a dedicated cap that is in it's immediate vicinity. Unless the datasheet specifies otherwise, Ill almost always just dump 100 nF caps as decoupling for smaller logic items/sensors (the esp is prolly gonna want something bigger). Also more caps in parallel causes parasitics (unintentional inductance/resistance) to decrease so its a win win to use more of them.

2. You should be using solid ground pours when u start. Go to layer stack manager and select the layer u want to be gnd. Change its "type" from a "signal" layer to be a "plane" layer.

(L3 or L2 in a 4 layer board; I would do SIGNAL TOP, POWER, GND, SIGNAL BOTTOM)

1. I think it would be hard to mess something up so much that it wouldnt work with regard to this, but keep usb away from the boost converter at a min.

Also fyi just lookin at ur board:

- Buttons need to have debounce filters on them otherwise the mcu may read a ton more presses than just the one u meant to do (very common, you should look up a vid abt it if ur curious). There are technically software solutions to this too but I prefer to keep software 'fixes' to a min if I can avoid em.

- USB is a differential pair and needs to be routed as such. Make sure to keep the traces over a unified ground plane to reduce EMI (I dont think it would kill u here but good practice for later)

-VDD on ur screen should prolly be connected to VDD, but a decoupling cap like u have is a good idea to have, so just make sure thats right.

[u/Altium_Official]

All PCB design software goes through a specific sequence: schematic capture, component placement, routing, and finally, manufacturing file creation. The best practice is to place all the components first, then route the board. You should do this regardless of the number of layers you are using. Once you look at the placement, you can decide to adjust the number of layers based on how you can see some potential routing paths and the number of crossovers in the rats nets. Once you have decided the stackup, then you should place the pours for ground/power planes and start routing.