Strategies for decreasing trace width in PCB

Question

I'm working on a custom alarm clock. For the display, I'm using an Arduino Nano to control a 7-segment display made of ninety Neopixels. I have some buttons and an encoder as well.

Based on a 60 mA power draw for each Neopixel and about 40 mA for the Arduino I've calculated a 5.44 ampere current. I want to design the circuit for 6 amperes current (the buck converter I'm using can provide 8, but I shouldn't need that much.) I want to use 1 Oz copper if possible to reduce cost.

The trace width will be 3.56mm for that, which is far too wide. Is there any way I can reduce the trace width?

An idea I had was to split the power input into two 3 ampere power rails, each connected to half the board's components. Would the two rail idea work?

Answer 1

Two-rail for both power and ground should work, but if you're looking for increased ampacity without increasing trace width or PCB dimensions, you can always apply solder to the trace to increase that one's current-handling.

Answer 2

I do not find 3.56 mm to wide, so it should not be a problem for the PCB construction. If you want to try to reduce copper width, you can do one (or more of the following):

• Increase the number of layers, keeping in mind that internal layers dissipate worse the heat than external ones. Connect internal and external layers with via stitching.
• Use heavy copper PCBs, but that would considerably increase the cost

For the 2 split power rails, it can work, but be sure that the current is well balanced between both rails

Answer 3

To quote the immortal Scotty. "Ye cannae change th' laws o' physics". In this case those are Ohms law (and the resulting power loss) and Onderdonk's fuseing equation.

You will just have to find a supplier that can supply heavier copper at a volume price you can accept.

A 'cheap trick', with diminishing returns, is to use multiple layers for the same trace. e.g. A 6 layer PCB is not much more cost than 4 layers but you'd get 33% more copper.

Another solution (that introduces it's own problems) is to use a thermally conductive PCB, e.g. AluClad but it would probably be cheaper just to use thicker copper.

Answer 4

You can "Load the tracks". This is an old timers term. Sometimes these are called Eltracks. What this entails is running copper wire along the hot track tacking down with the soldering iron. Thru hole componant leads or even fuse wire can be used it a pinch. This is an easy way for 1 or 2 prototype boards but not recommended for volume production.