PCB routes width

Hello!
On the internet there are a lot of people saying different things, so I came here to be sure.
Using 5v/3.3v what width should my PCB’s routes have?
I’ve found these:

  • Power: 0.625mm
  • Signal: 0.3mm

I’m obviously trying to keep it as compact as possible and I’m gonna buy them here.

Thank you!

1 Like

(deleted)

They all ask about Amperes and I don't really know much about them..

Check your board manufacturer's capabilities[/u]** (5mil for 1 & 2-layer boards).

Of course, if you push the manufacturer to their limits you are more likely to get errors/failures.

I assume you can find recommendations for power traces on the Internet. The resistance depends on the width and thickness of the copper. Again, if you "push it" you may have problems. You might want to take "worst case" short-circuit current into account... You wouldn't want a short to burn-out a trace.

Thanks, but...

Let's make an example: I need a PCB to connect a Servo to an Arduino, so the PCB would look like this:

  • 3 male pins (5v, GND, signal);
  • 3 female pins (5v, GND, signal);

Now, let's route this.
5v -> 5v with .625mm trace width
GND -> GND with also .625 trace width

And then we need to know how many amps does the servo need, if I understand what you two are saying. Am I right?
If I'm right, the best thing to do is probably use a meter... but what do I have to connect to what?
As far as I know the meter has a GND (black wire) and a Vcc (red wire), and I need to have an entire circuit to make it work. Do I need to connect GND to GND and Vcc (red wire) to.. what? Servo's white wire (signal)?

Then I would be able to use a PCB trace calculator as @spycatcher2k said.
Is this one okay for that?

These are my doubts, hope you know the answer xD

“- Power: 0.625mm - Signal: 0.3mm”

There is very little benefit to use small width traces.

Suggest you use 50-75 mil traces for most common power traces, GND plane for 0V.

When going in between I.C. pads, traces are narrowed but no need to keep them narrow for the full length.

In general, I use reasonably larger traces than you stated. 75mil power, 25ml signal. (1-2oz copper)

You must measure or estimate the amps. Without that you are only guessing.

Many small servos use about 1 amp. So run the trace width calculation for that current with the thickness specification from your board manufacturer. Pick a low but non-zero temperature rise. Maybe 5 degrees C. That will give you a conservative (wide) trace.

Usually you will get very small numbers from the calculation. If it makes you feel better, make the traces wider. Trace width is free with most manufacturers. So the trace can be as wide as the board. Use "fill" polygons for ground and sometimes power.

larryd:
In general, I use reasonably larger traces than you stated. 75mil power, 25ml signal. (1-2oz copper)

Are you sure?
This width is so big!

I attached an image with 75 mil trace width and it’s so weird to me

MorganS:
You must measure or estimate the amps.

As I mentioned in post #4 I'd do it if I knew how to use a meter.

you need to use the data sheet.

one way to think about it, is to make all your traces small.
that way, they burn up if you do something silly like try to power a motor from a pin.

The main Arduino use is to send small signals to other things.
the signals for a motor driver, the relay module, those things use the power for an LED, just a few mA

what you are saying is you want to buy transportation.
we are saying, is this to get you to the mailbox ? or are you taking a family of 3 to the beach ? or are you hauling massive truck of goods across the continent ? did you say, roll, fly or float ?

knowing AMPs is not optional. it is the single value that is required first.

also, every part you can buy has a data sheet. the things that carry power, resistors, diodes, capacitors, etc, will have max values.
the things that consume power, lights, motors, etc, will have max values. you can look at the data sheets of your parts and then round up on the Trace Width Calculator. don't forget that thicker copper can make the trace narrower.

I am with larryd, I go for a fatter trace as my standard. for my auto-route software, I found that fatter traces incurr more direct routing and less turns. I often try different widths to see what the results are before I hand-route.

Thank you!
This is a Servo datasheet.
The maximum mA that it can reach is 1100 mA (So 1.1 amperes).
I put this value in the calculator as you suggested, I used this.

Inputs:

  • 1.2amps
  • 16mm thickness (probably I'm wrong here: what thickness is this? The PCB thickness?)
  • Temp rise 5 celsius

Results:

  • External layers: 0.0507 mil
  • Internal layers: 0.132 mil

These are ridiculously small, where am I wrong?
I followed you instructions.

My objective is to print these PCB to not use a breadboard in my project because I need it to be as small as possible.
Thanks

dave-in-nj:
what you are saying is you want to buy transportation.
we are saying, is this to get you to the mailbox ? or are you taking a family of 3 to the beach ? or are you hauling massive truck of goods across the continent ? did you say, roll, fly or float ?

I didn't catch this part, maybe it's because of my low level of English

If you cut through your PCB with a saw you would see the copper traces at the saw cut. They will be very skinny rectangles. They have a width (what you see designing the board in your software) and a thickness.

Sometimes the thickness is given as the weight of copper per square foot of board. 1oz (ounce) is very common. This can be converted to a thickness in inches or meters. 1oz = 1.4mil = 35um

nicolopadovandev:
Are you sure?
This width is so big!

I attached an image with 75 mil trace width and it’s so weird to me

Why do you care whether it “looks weird”? If you want to limit the losses and temperature rise to about 5°C those traces can not carry more than 2.8A (I assume a standard 1 oz/ft2 copper thickness). For a project I am currently building I’m using 4 mm (about 160 mil) traces. They’re supposed to carry up to 3A. 2 mm would do but I have the board space so why not.

Those 4 mm traces don’t go to ICs, that wouldn’t work well. Too big. For the power to the ICs I’m using 1 mm traces. Signals are 0.5mm traces - on that board the fastest signal is 9.600 bps Serial, trace width doesn’t really matter at those low speeds.

But when designing using SOIC packages you will find you have to reduce the width of the traces leading to that IC even more or it just won’t fit.

To find the current of your servo: look it up in the data sheet, or measure it. The current it draws determines the minimum width of your traces.

It's weird because that width doesn't allow me to do anything. Too big for this board...
Also it's my second pub (the first one burnt) so you all shouldn't say things like their obvious...
I didn't understand how to know the thickness also.

I'm sorry if I'm being tedious but I'm not understanding a lot of things so.. sorry :frowning:

I didn’t understand how to know the thickness also.

That’s a parameter that you normally have to select when ordering a board. You really have to do your homework better! If you don’t know how a PCB is built up or how trace width is determined, read up on it. Lots of information is just a quick Google search away.

At 1 oz/ft2 a 21 mil (0.55 mm) trace is the minimum for 1.1A (5°C temperature rise). But for longer traces it’s better to make them wider, less losses. I’m using the KiCAD trace calculator to get these numbers.

Do switch to SMD parts instead of THT parts. That saves far more board space than trying to skimp on trace width, without compromising the overall design. Just a switch from DIP to SOIC makes an IC take half the space. A 0805 resistor is a fraction of the size of a regular 1/4 W THT resistor.

So thickness is only the "height" of the circuit..

nicolopadovandev:
So thickness is only the "height" of the circuit..

Yes.

The first attachment is a .2mm trace width

The second is a 2mm trace width

That’s why I said that it looks weird: connections that shouldn’t be linked one to another are touching.
Do I make the pcb bigger?

This is only to show you, it’s not the width that I’m gonna use

Also see post #10. 16mm thickness and 1.2amps = 0.0129mm required width.
This has no sense following what you said, so I'm wrong somewhere