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EDA => General PCB/EDA/CAD Discussions => Topic started by: dmills on January 21, 2018, 11:21:45 am

Title: MC Pcbs and connecting to the metal base?
Post by: dmills on January 21, 2018, 11:21:45 am
Having somehow never done one of these before I have a manufacturing question.

Given a single sided metal 'core' PCB of the sort one might use for LEDs or such (Actually I want to use it for some GAN Systems parts in an experimental power converter), is it possible to via thru to connect to the metal base plate to use it as a ground plane, or do I need to go to a two layer stack? 

I can see that vias should be possible with a copper substrate, but does it work with aluminium?

Anyone have any experience with these, or in fact with the bottom cooled GAN Systems parts?

regards, Dan.
Title: Re: MC Pcbs and connecting to the metal base?
Post by: filssavi on January 21, 2018, 11:38:36 am
I also took a look at metalcore for power electronics but as far as I know it is not possible to do what you ask with usual manufacturing processes, you can do either normal boring and relatively cheap single sided MCPCB or if you need more routing layers (I guess) for planes or whatever you need to go to a dual layer mcpcb (basically a normal dual layer PCB manufactured on a thin prepreg glued to an aluminium plate) these are a lot more expensive (at least 2X the cost in volume) and have worse thermal properties

Title: Re: MC Pcbs and connecting to the metal base?
Post by: dmills on January 21, 2018, 11:48:56 am
I was sort of hoping for a thin double sided core made and then bonded to the metal plate, no need for insulation between L2 and the plate, it is just the desire for a ground plane and small loop areas.

Oh well, back to the drawing board.

Regards, Dan.
Title: Re: MC Pcbs and connecting to the metal base?
Post by: filssavi on January 21, 2018, 12:10:37 pm
There is also that kind of multilayer mcpcb, even though i’m not shure you can have PTH vias, the same considerations as far as cost apply

More in general I think you can do whatever you want, if you go to a suitably high end pcb manifacturer, the real problem is that all these solutions are very expensive and you severely limit the choices of pcb manifacturers you have, this can of course be fine in some sectors where cost are not an issue (aerospace and military is what springs to mind)  it will be less so in other fields

Title: Re: MC Pcbs and connecting to the metal base?
Post by: SeanB on January 21, 2018, 01:16:37 pm
How about a MCB with single side and then a flexible PCB that is basically the jumpers ( and perhaps low power devices as well) that is placed over the main board and then soldered to it. Single sided would have to have the solder side on the side facing the MCB but they are also available in 2 sided versions these days.
Title: Re: MC Pcbs and connecting to the metal base?
Post by: dmills on January 21, 2018, 03:27:29 pm
Might as well go for a copper sheet cutout as a ground busbar if I was going to do that, but I am looking at several kW of power at MHz switching rates, so ground really does need to be a buried plane, and even then there is a reason this thing is an experiment.

I might just get a 0.8mm FR4 job done as 4 layer with 70u copper and bond that to a hunk of metal with some thermal adhesive and a bookbinding press, it will do for the experiment.

Regards, Dan.