# Layer stack up & thickness calculations for Metal-core PCB

I am designing a single layer metal core PCB for putting high brightness LEDs. Does anyone know how the layer stack up for such a PCB are common? How is the metal core thickness decided? I mean what are the heat calculations required? A White paper/Journol/ or an article will be very helpful.

I have a power dissipation of about 7-8 W & PCB area of 30cm x 6cm=180cm2.

Thanks!

No doubt there are many options, but the best thing to do is to find a board house that does Al PCBs and call them. Designing /w cooperation from your manufacturers is going to save you a lot of headache.

Here is a link to Henkel's Al PCB product datasheet, just to give you a heads up of what all is in a metal PCB: http://www.bergquistcompany.com/pdfs/techLibrary/tclad_2013_web_fullguide.pdf

• Thanks, I had already come across a similar pdf from henkel but yours seems to be more descriptive. But again there are no calculations or user guides to choose PCB thickness. – Akash Neel Dey EEE Feb 3 '17 at 11:34

THe heatsink is effective if all area is radiating. So two options- make it thick or attach to something. If you think, the area itself is enough, 2mm PCB should be fine, 3mm is better. If your power is higher (look for the equation of power dissipation through surface area) make the PCB thinner (1mm maybe) and attach a heatsink with fins (don't forget thermal paste). So again, the thickness of the plate will be 2-3mm, and surface will be enlarged by fins.

Of course there are more advanced options- like fans, heat pipes, water cooling, etc...

Upd. I haven't perform a calculation, but it seems like you don't need fins with your geometry, just make the plate 3mm.

• Yes, I believe 2-3 mm Al is enough for standalone passive cooling. But, can you share some sample (basic) calculation sheets through which I can be more sure of my system level thermal conductance from junction to ambient. Further you told about Heat pipes, I too have heard of their effectiveness, but I'm not sure if they are cost effective. Would like to read about them too... :) – Akash Neel Dey EEE Feb 3 '17 at 11:38
• Ok, refer here for basic equations. formulas.tutorvista.com/physics/… this will give you feeling of K and A. But you have to understand, that it's mostly about making all available A effective, this is why you transfer heat across the board by either thickness or heat pipes. By the way, it's best to Google heat pipes, see pricing on aliexpress. – Gregory Kornblum Feb 3 '17 at 11:46