Help needed in making custom Rebel MCB with mounted Rebels

mds82 · Aug 9, 2007

I am looking to make a custom Rebel board with the Rebel's mounted already. The overall dimensions for this board would be 1 inch high, 0.7 inch wide

In the past i did the exact same thing with the Cree XR-E LED's and LEDlightingsupply was able to make the mcb for me and mount them as well

Would Luxeon be able to do something like for me AND mount the LED's

i would be driving all of these from a buckpuck 3023-dn-700 running 3 in series and both sets of Led's in parallel. the power source would be 12v, being used in an Automotive application

mds82 · Aug 15, 2007

here is what it would look like

frenzee · Aug 15, 2007

I doubt Lumileds (who makes the rebels) would take orders for cutom-made MCPCBs. They just aren't in the business of making PCBs - thier main business is making LEDs. Did you already check with the guys at LEDlightingsupply? Also, if you have the time and the patience, you could make your own one-off MCPCBs. In fact you can choose your own substrate material (i.e. copper) which is much, much better than the aluminum core variety in terms of thermall conductivity and thermal mass.

mds82 · Aug 15, 2007

LED lighting supply - i thought they only deal with Cree LED's not with Luxeon's

also i dont have the ability to create a board on my own, i dont have any resources available to me to make something like this.

frenzee · Aug 15, 2007

mds82 said:
LED lighting supply - i thought they only deal with Cree LED's not with Luxeon's.

I don't know. I assumed since you were talking about a custom design, they would have to start from scratch, in which case they would be able to use any LED or pattern you sepcify. I know that there are protyping shops like this one, who can fabricate just about any design as long as you supply them the Gerber files and I believe they can do the assembly also, but my guess is it won't be cheap. There was a "shop" on the UK eBay that used to advertise PCB fabrication in China at very reasonable prices, but the link I had in my bookmarks is expired now and I couldn't find it doing a quick search. Sorry.

Oznog · Aug 15, 2007

Lumileds has a suggested design for PCB-cooled Rebels, and that is NOT it!

First off the thermal pad is under the dome. PCB foil has a limited ability to spread out the heat so the available surface area can dissipate it into the air. Clustering the thermal pads beside each other leads to their heat combining, yielding high die temps no matter how big the board is. The thermal pads should be far enough apart that the localized hot spots around them do not overlap and combine, I kinda picture 3/4" or so but I don't know and it depends heavily on foil thickness anyways.

The second part is Lumiled's board used an array of plated throughholes near the die to provide increased surface area. When done properly this can dramatically decrease thermal resistance to ambient air. I'm not sure how well this works if it's only going to be mounted on a flat surface that prohibits air from flowing through the holes from one side to the other, but even without that I suspect it's still pretty good for thermal impedance.

They also used a gold plated board, so it doesn't need to be coated with trace masking which would dramatically increase its thermal impedance and won't show the oxidation problems of exposed copper trace or tinned soldering pad.

kanarie · Aug 16, 2007

fyi: already had a look at these triple Rebel stars ? (parallel and series )

SemiMan · Aug 16, 2007

The thermal vias are there to transmit heat from the front of the board (and the LED) into the back so that you can effectively couple the board to a heat sink as opposed to using and expensive metal core board. It is not meant to increase surface area by having air move through the holes. You can get pretty low thermal impedance this way from the LED to the back of the board. I metal core board is still better and if you plan to put three LEDS so close together and run them at a relatively high current, I would suggest that you need a metal core board for it to work properly. At a minimum go for thick copper...at least 2 ounce.

Semiman

Oznog said:
Lumileds has a suggested design for PCB-cooled Rebels, and that is NOT it!

First off the thermal pad is under the dome. PCB foil has a limited ability to spread out the heat so the available surface area can dissipate it into the air. Clustering the thermal pads beside each other leads to their heat combining, yielding high die temps no matter how big the board is. The thermal pads should be far enough apart that the localized hot spots around them do not overlap and combine, I kinda picture 3/4" or so but I don't know and it depends heavily on foil thickness anyways.

The second part is Lumiled's board used an array of plated throughholes near the die to provide increased surface area. When done properly this can dramatically decrease thermal resistance to ambient air. I'm not sure how well this works if it's only going to be mounted on a flat surface that prohibits air from flowing through the holes from one side to the other, but even without that I suspect it's still pretty good for thermal impedance.

They also used a gold plated board, so it doesn't need to be coated with trace masking which would dramatically increase its thermal impedance and won't show the oxidation problems of exposed copper trace or tinned soldering pad.

lotsaluck · Aug 16, 2007

Easy to do with heat sink. I can CNC one up but whats it worth to you (worth my time doing it) and would you want to do two of them in order to share? LOL
email me for more discussions on it is best.

frenzee · Aug 16, 2007

SandwichShoppe just added some rebel PCBs, but no pictures.

Argofanatic · Aug 17, 2007

This looks like an exact math for ya .
http://www.luxeonstar.com/sub_category.php?id=1430&link_str=1430

daywalker · Aug 18, 2007

I like the PCB's from Led-Tech better, because they put the emitters closer together. Soon i will try that setup with 3 LE
in a 2C host. I hope the Mag reflector will do a good job.

Help needed in making custom Rebel MCB with mounted Rebels

mds82

Enlightened

mds82

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frenzee

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mds82

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frenzee

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Oznog

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kanarie

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SemiMan

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lotsaluck

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frenzee

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Argofanatic

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daywalker

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