PCB trace width

[adding_to_the_noise]

I 'm designing a pcb for a tonepad tubescreamer using Eagle from Cad soft. It was brought to my attention that the traces need to be made the correct width for the current and voltage of the circuit. Exactly how do i find this information out and is there a standard width that most stompboxes use for pcbs?

[Gilles C]

Some good info here.

http://www.pcbdesignandfab.com/guidelines.htm

Gilles

[Dave_B]

Some good info here.
http://www.pcbdesignandfab.com/guidelines.htm

Added to the Wiki.  Thanks, Gilles.   

[Processaurus]

I started learning to make PCB layouts this last week, my pops (an old timer EE) turned me on to making the ground traces nice and fat (50mils) to have the lowest resistance possible from end to end.

[JimRayden]

I started learning to make PCB layouts this last week, my pops (an old timer EE) turned me on to making the ground traces nice and fat (50mils) to have the lowest resistance possible from end to end.

It's not just a game of resistance, you also have to deal with capacitance between the traces. The wider you make the traces, the smaller the space between them gets, the higher the capacitance. It's about balance between the two properties. I'd still make them quite wide because resistance goes up more quickly than capacitance.

But when we talk about stompboxes, these are mostly of very small importance and will generally not affect the operation of the circuit. More importantly you'll have to deal with the high gain traces emitting EM field to the rest of the circuit and thus cause oscillation.

I'd make the trace widths and the space between them equal. Or the traces a tad wider.

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Jimbo

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Jimbo

[grapefruit]

I use 20mil track width for "normal" tracks and 30,40 or 50 mil for ground or power tracks, depending on the room, lenghth of track, and current draw. I use normally 15 mil clearance. These days I generally use a ground plane, but that's using a double sided PCB. 10 mil clearance is usually ok, though we've had shorts to the ground plane with some runs. After changing to a new PCB manufacturer this was largely eliminated but it still happens sometimes.

It's important to think about what is going down each track so you know when to keep tracks away from each other. ie: keep low level input tracks away from high level output tracks to avoid oscillation.

Your minimum track width and clearance is ultimately determined by the how accurate the manufacturing of the PCB is.


Stew.