5A current, PCB trace width?

Question

Hi. Suppose I want to run 8 string of around 5A current on a single board. What kind of trace width should I select? Does it matter what the spacing between each 5A trace on the board? Is it better to have it run in mid-layer? The free version of Eagle only suppose 2 layers. Does AutoCAD Electrical support mutilayer PCB design? My school offer AutoCAD Electrical for free, but I have never use or know anything about it. Thanks!

Answer 1

Like anything else, you're dealing with power loss issues, so the internal trace will need to be much larger than an external trace to allow for Newton's law of cooling.



If you're using 2 oz/ft^2 copper, an internal trace will need to be 147 mils and an external trace 54.5 mils.

That's for 5 amps.



1.378 mils/oz



Spacing only matters for distribution of heat, but that is why the trace is wider, so there is no technical limit to the separation, but you do need to take potentials and mutual inductance/capacitance into account if it matters.



Edit:

It's a give-and-take environment here. Most don't give out the points after they receive the information they're seeking. They just keep asking more questions. Hardly seem right.

Answer 2

Pcb Trace Width

Answer 3

AutoCad electrical will be no help in PCB design, it is used for generating electrical drawings for industrial automation (integration, not board level design).



try Kicad, it is free and easy to learn. there is no limit to size of the board, does up to 16 layers, etc. It also has calculators you refer to. to carry current, you need conductor of sufficient ampacity (cross section). flat conductors like on PCB have greater cooling surface area and can carry a bit more than round conductors (wires) for example. to tell more we need to know thickness of copper layer (cladding). unless specified explicitly, most PCB shops will assume that your standard is 35um or 1oz/ft^2. at this thickness of copper, trace will need to be 2.76mm.



commonly available copper clads are 0.5-4oz/ft^2.

thinner copper layer means sharper features (finer details on the board, because layer is thin and effects of lateral etching are negligible). for power, you may need to choose 3 or 4 oz/ft^2 or multiple layers. note that inner layers are surrounded by PCB so they cannot dissipate heat nearly as good as surface layers.



space between traces is insulation. it defines how high voltage can you run on the PCB without running into problems (creepage current). the higher the voltage, the greater the space between traces need to be.

Answer 4

About 7mm width trace.