Determining trace/via/wire current capability

[pedja089]

Put vias under component. Make bottom copeer pad large, and you have much better heatsink capabilites.
Make via also untinted ut botom, so you can fill it with solder. For my taste your trace to via are too small(I know it is only signal, but...).

[Ioannis]

I understand that you use Eagle.

How can you prevent solder mask at the area of the VIAS under the smd component?

Ioannis

[pedja089]

Yes it is eagle...

[pedja089]

Also, you can draw any shape on that layer, and solder mask will be removed from that area.

[Ioannis]

Great!

Thank you,
Ioannis

[Demon]

Put vias under component.

How is this?

[Demon]

I went one further using vias after adding cooling; grounding the VSS pin on the voltage regulator with 3 large vias.

This way it doesn't mess up the smaller vias I have on signal traces and VSS pins on tiny SMD ICs.


CORRECTION:

These are labelled backwards. The 7805 uses the TO-263 package and the Hexfet uses D2Pak (in my project).

[Demon]

... For my taste your trace to via are too small(I know it is only signal, but...).

JLCPCB can support up to 0.15 vias. I'm using 0.3 hole/0.5 pad since I'm using 2 layer PCBs.

https://jlcpcb.com/capabilities/pcb-capabilities


I'm not finding any "ideal dimension" for signal traces on the web...? They seem unanimous to say "however small your PCB fabricator can handle".

I'm using:

- 0.2 traces default,
- 0.3 for USART/USB,
- 0.3 for VDD.

[Ioannis]

I'm not finding any "ideal dimension" for signal traces on the web...? They seem unanimous to say "however small your PCB fabricator can handle".

PCB design is a bit of art. So, rules do apply but you can bend them (within reason of course) using common sense.

Nice touch the cooled grounding. Never thought of that. Though I do not know how much will contribute in cooling if the main tab is big enough.

Ioannis

[pedja089]

Top is usualy bit tight with space, So I make GND al large as I can on bottom.
Uart usualy don't require any special routing. I usualy use trace width of smalest IC pad.
For USB it depends on lenght. It usualy doen't meter. But if it is long, it is critical to have diff pair with proper impedance....

[Demon]

...USB it depends on lenght. It usualy doen't meter. But if it is long, it is critical to have diff pair with proper impedance....

I read that people have been getting away with what they consider sloppy traces.

My USB traces are 20cm long, running side-by side, far from any large current. My application does not have to support USB 3.0, 2.0 is plenty fast for me.

[Demon]

... Nice touch the cooled grounding....

The vias in the VSS pin is not for cooling; it's just to get the current to the bottom side with more via conduit.

If I increase VSS via size, it messes up my spacing close to the TSSOP ICs.