Hi all,

I’ve recently built a prototype for my project, “SolarBeam Charger” .... a compact high-efficiency solar USB charger. The current prototype uses a standard FR-4 PCB with 2 oz copper ..... but its hitting thermal limits during high-current usage

I’m considering switching to either:

1. A heavier copper PCB (4 oz)
2. An aluminum (metal-core) PCB

I know the basic diff between the 2 ...... read online resources:
https://www.aivon.com/blog/pcb-type...opper-core-pcbs-for-optimal-heat-dissipation/
https://www.mclpcb.com/blog/aluminum-vs-copper-pcbs/

but never have worked on Al PCB before.

Has anyone worked on a similar high-current, small-footprint prototype .... please share insights on which PCB type gave better performance?

Thanks!

 

A trick that I have seen once for heat removal on a PCB was an array of copper "flags" soldered to the board wherever there was room. Thatexampl used half inch wide copper strip cut into sections about an inch long. Another example used sections of bare copper wire, from scraps of #14 solid wire, soldered to the PCB abd extending up alost an inch. Both were described as :" cheap, easy, effective, and a bit ugly." So that is one option.

 

Thanks for the idea .... but wont work for me ..... adding copper “flags” or wires like that is pretty impractical, messy .... impossible to scale for production.

I m looking for more compact, robust, and repeatable solution .... thats why looking at heavier copper or a metal-core PCB to handle the high currents cleanly.

 

OK, one other suggestion is for longer leads on all of the components so that they are not hard against the PCB. That will allow a bit more air circulation. I have seen that done on production PCBs, but not very often.

 

first of all where does the heat come from? is it from some component (IC, MOSFET, IGBT) or the PCB tracks themselves.
if the issue is with the PCB, using wider tracks, bus bars etc can help. otherwise heat need to be taken away from the component that is overheating.
for fully passive cooling, use ALU or CU board and possibly attach heatsink or heat spreader.
ALU is cheaper and more common - easy to get some boards to test and see if this is sufficient or not. another option is to add active cooling (fan).

 

Please post a picture of the top layer of the PCB. Pick a hot spot. Designing a power PCB with little to no heatsink is not like a computer PCB. You must break many of the laws that have stood for years.

 

absolutely. without sharing where the hotspots are, we can only shoot in the dark...
one more thing that could help is so called bus bar.
main function is to route high current and thus reduce heat generation in the first place and then dissipate it. sometimes they also serve as stiffener (rigid types only, not braided bus bar).

 

ithout sharing where the hotspots are, we can only shoot in the dark

If they get hot enough, we will be able to see them from across the street.

I have seen some exciting fires.

 

...and through closed eyelids. ;-)