Aluminum/MCPCB suppliers?

[samsonc]

Hey guys,
Anyone have personal experience with any MCPCB suppliers? I'm designing a board that really needs good thermal conductivity. I still have to do some thermal measurements, but the last board I ordered from a random Asian supplier (Sitopway) seemed to not /really/ be a proper, thermally conductive MCPCB. As far as I can tell, it's a thin layer of FR4 glued to an aluminum baseplate (if this is actually how some of the thermally conductive baseboards are, I'd like to know--I'd assumed it'd be something white and without fiberglass reinforcement, being ceramic filled). This particular supplier couldn't provide data on what baseboard material they even used or where it came from.

Thanks!

[DerekG]

I'm designing a board that really needs good thermal conductivity.

No experience with MCPCB, but if the supplier can't supply you with any definitive heat dissipating specifications, then you cannot rely on it.

Other options for better heat dissipation are:
1/ Specify 3oz copper instead of the usual 1oz;
2/ Open up the bottom layer tracks/bottom layer heat sink areas so that they are covered with solder during wave soldering;
3/ Open up the top layer solder mask & paste screen for tracks & heat sink areas so that these areas will be filled with solder paste. This will increase significantly the heat dissipation. Specify a 8 thou paste screen & if your board areas are quite large, consider a "grid arrangement" within the screen to prevent large bubbles forming during the infrared reflow process.

[jmole]

I'm designing a board that really needs good thermal conductivity.

2/ Open up the bottom layer tracks/bottom layer heat sink areas so that they are covered with solder during wave soldering;

Terrible idea if you're mounting the back of the board to a heatsink.

[samsonc]

Sorry, this is a weird hybrid mechanical/electrical/thermal application and an MCPCB is necessary. Just wondering if anyone has experience with MCPCB suppliers. It was indeed a mistake to go with the first supplier, who didn't even have thermal specs, but it was worth the risk given how little they were charging for the board (I honestly don't feel bad that it wasn't great, and that remains to be seen anyway). Now I'm just looking for a supplier which anyone has good experiences with.

[samsonc]

If anyone's curious, just for reference--the boards I got from Sitopway are half 1/2oz and half 1/3oz. This actually would've been useful for us (I don't know anyone who will put 1/3oz on MCPCB!) but my guess is they found some old scrap thin laminate material lying around and just pressed it with some prepreg onto Aluminum.

They were /really/ cheap though...

[poorchava]

I had something to do with MCPCB (but I don't claim to be an expert on this by any measure).

In general same as with normal PCBs there are two ways to fabricate an MCPCB: lamination and build-up. First means that you'll have a thin layer of FR4 with races on it (can be multi-layer). The FR4 can be really thin, as in 0.2mm or so. Second way is to do it micro-via style, which means that dielectric is deposited from liquid form. Those layers can be thinner (better thermal conductivity), but usually so are the traces.

I haven't had any experience with chinese MCPCB manufacturers - everything was done locally here in Poland. With such things it's better to have a good communication with the manufacturer.

[samsonc]

Seems like I literally picked the worst possible supplier. It seems as if it actually takes effort to run into a company in China who knows this little about making an MCPCB (I think I've heard okay review of Sitopway for their normal PCBs). Again, they were clearly doing lamination, but their laminate is almost certainly just thin, plain, non-thermally-enhanced FR-4/CEM/whatever. And they managed to use three different types of boards (I can tell by the resistance of the copper clad), none of them 1oz, for the order (I had 10 panels). To be fair, I still have to measure the thermal conductivity of the material, but the copper weight is definitely completely out of whack.

I came up with a list of 10-20 MCPCB suppliers (in China), and everyone who's responded is charging less or the same amount for the board, and most of them have datasheets with specs on the material... The other supplier I considered, Gold Phoenix, was charging some insane amount (more than any supplier that I've asked afterwards) for the same board. This is partly why I thought Sitopway was so cheap when I first looked. Gold phoenix had sent specs, by the way--but they were pretty lackluster.

As a side note, I've always had excellent experiences with Gold Pheonix when it comes to their standard PCBs. They're more expensive, but they do fast turn and the quality of their boards (silkscreen and especially layer-to-layer alignment) has been excellent.

Just went out and tried one of the suppliers that seemed capable and cheap. *crosses fingers*

[gregariz]

Farnell stocks a aluminium PCB substrate

http://uk.farnell.com/cif/aat10/pcb-prototype-aluminium-100x150/dp/4147984

[IconicPCB]

We make PCBs..

Had a client who needed enhanced thermal conductivity. The design was built as a laminated board onto 1 mm thick copper plate. Components which were in need of dissipating a lot of power had FR4 milled beneath them and theywere positioned in direct thermal contact with copper substrate.

Send Your gerbers and design instructions to sales@iconicpcb.com for a quote.

www.iconicpcb.com

[Corporate666]

I can recommend Myro PCB (www.myropcb.com).

No affiliation, but I have been a customer of theirs for around 15 years.  I've had MCPCB's made by them before.  Two that come to mind were a 2-sided MCPCB in 0.031" thickness that had some vias on it.  It was more expensive than FR-4, but not too bad... IIRC it was something like $0.25 per board in qty 500 (the boards were small - perhaps 0.3" x 1.5"), although I seem to remember there was a few hundred dollar NRE fee.

I also had a single sided 0.062" MCPCB - traditional star arrangement with one side left bare. 

It is a "real" MCPCB - not just an FR-4 board laminated on.  I believe they silkscreen epoxy onto the aluminum substrate and copper plate over that... then etch the board as usual.   So all you have between your solder layer and the aluminum substrate is a thin layer of epoxy.

I think you said somewhere that you need the mechanical strength as well, but if you are concerned about thermals, look at some of the app notes from Lumileds.  They have a lot of testing with 0.031" FR-4 PCB's using arrays of vias around heat generating components, and they were able to achieve better thermal performance than by using MCPCB's.   They go into great detail about the specific design features and their contribution to the overall thermal performance... the most important being a few small (0.010" or less) vias directly in the thermal pads of the heat generating components, as well as using thermal epoxy filed vias (or copper filled vias).

FWIW, Myro PCB offers both copper plugged vias and thermal epoxy filled vias.