aluminum pcb fabrication - anybody tried it yet?

[oakgraphics]

Howdy gang,

Okay - looking at the LED projects out there I am thinking of making a luxeon Rebel type of RGB+W matrix. Judging from the heat levels, it looks like I either need to make a big PCB, or a smaller PCB that has better thermal displacement properties the FR4. I have noticed lots of luxeon 'star' PCBs out there and they use an aluminum clad board. Has anybody seen a PCB maker that can make aluminum clad prototypes? :-) My net searches show there are some companies out there (all in china) that can do this, but I have not found a prototype run place for this type of board. (might not find one as this seems a bit specialized. :-)

[Matt_Edwards]

the only experience we had with similar substrate was with PTFE in Al and Brass
I would image you could just do a 0.8mm board with a solid ground plane on the back. the board would then be glued on to the substrate using conductive epoxy.

However I am starting to think this is getting outside the realms of DIY. If I remember correctly, Conductive Epoxy was a pain to use, requires special handling procedures (it is not good for your health), had to be store in the fridge, had a shortish self life and needed tight temp control in the oven.

But what is stopping you from designing the normal PCB board, preferable with no tracks on the bottom side that you use a number of nuts and screw to hold on to the AL. you would apply heat sink compound inside the sandwich.

[Entropy]

You may want to look at Luxeon's app notes on Rebel mounting. The Rebel's packaging was specifically changed to permit use of FR4 boards instead of MCPCB. I have not seen anything covering DIY MCPCB work anywhere.

[sparky3]

have you seen this http://www.bergquistcompany.com/thermal_substrates/t-clad-product-overview.htm, you would have to mill it. but it looks promising. i have not tried it yet but one of the guys on cnc zone under pcboard milling was going to start working with it.

Rob

[Cheater]

http://www.dealextreme.com/details.dx/sku.4512
Grab them if you have bare LEDs.

For 3 watt Luxeons I find that a nice large computer chipset heatsink is the only thing that keeps it cool.
Some thermal paste and epoxy glue to hold it in place.
It also makes positioning quite flexible.

Just with the aluminium star, it takes about 2 mins before it melts the solder holding the wires on.

[oakgraphics]

http://www.dealextreme.com/details.dx/sku.4512
Grab them if you have bare LEDs.

For 3 watt Luxeons I find that a nice large computer chipset heatsink is the only thing that keeps it cool.
Some thermal paste and epoxy glue to hold it in place.
It also makes positioning quite flexible.

Just with the aluminium star, it takes about 2 mins before it melts the solder holding the wires on.

wow! that's good to know about the temps. I had looked into some sort of thermal management and judging from what I have found, a whole cluster of rebels requires a pretty large heat-sink. Digikey has some 1" x 12" heat-sink bars that are for LED use, and I could use that for a series of stars I supose if I don't make my own PCB for it. I have the lumileds guide for PCB mounting on FR4 and might give that a try first, and use the thermal via's trick to get the heat to the heatsink.

Here is my current layout. The heatsink fits on the back and there is a pour layer "TH" on both the front and the back that all the vias are attached to. This should give the thermal pull needed to bring the heat to the heatsink behind the board with some thermal paste.

[Cheater]

I'm not sure how well that would work.

The heatsink I've used was about a 1'x1'x1' cube with large fins and it still got quite warm to touch.
That is with a single 3 watt led on it.

[oakgraphics]

The unit should run at no more then 104f (40c) as that is the break-point for lumen effectiveness when run at 700ma. If I go 350ma current then I could run the units up to 176f (80c). I guess I better figure out the formula for how much heat-sink is needed per rebel. :-)