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Grounding aluminium PCB substrate
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Amper:
Hi!

Im recently doing quite a few high power circuits on aluminium backed substrate and since its mostly lower voltage stuff id like to ground the pcb or even use it as a groundplane.

Is there any industry accepted method for doing so? Id like to glue the pcb to a heatsink with thermally conductive epoxy, screws are usually difficult inn my applications.

I thought about using soft aluminium solder like its some times used on lithium pouch cell terminals. Just drilling through the dielectric in the required place like a via, put a drop of the special solder in the crater and reflow the entire board after assembly of the components.

Does anyone have experience with this kind of think?

cheers A.
viperidae:
To solder aluminium, don't you need to remove the oxide coating first? The one that forms in seconds when exposed to air.

Googling how to solder aluminium comes back with results that suggest it's quite difficult without specialised machines
Amper:
There is special solder with an unusual flux core that can break that oxide layer and solder aluminium like bare copper using a normal soldering iron.
Alex Eisenhut:
You can buy flux for lead soldering to aluminum and it works quite well, but it's hell on the iron tips.
ConKbot:
You want a "direct thermal" "direct copper" or "copper pedestal" MCPCB. It is used in better quality MCPCBs for LEDs. The thermal pad in the center of LED footprint is copper plated onto the core directly, rather than isolated by the dielectric layer. This will give you a nice selectable copper pad rather than having to deal with nasty corrosive fluxes for aluminum.
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