Power Led strip heat trasfering suggestions

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#1
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Hi there,

I am on design state of a product using 6 power LEDs (1W). Unfortunately, the LEDs at 100% of luminocity produse high temperature level. There is no problem for us to drive them at 80%, but not less.
The Led strip pcb will be double sided, using the bottom side just for heat transfering.

kindly advice, what is prefered:
1. The bottom pcb layer as a heatsink to be cover by a mask layer or
2. to be free to be soldered via the wave process

Please tell me your suggestions based on your experience on issues like this.

Any other idea is acceptable.

Thanks for your time,

Michael.

Michael.

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What is the package of the LED that you are using?

If you think education is expensive, try ignorance.

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The datasheet can be found at
http://www.cree.com/products/pdf/XLamp7090XR-E.pdf

Michael

Michael.

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Check out the Luxeon web site for info related to their Star, (and other), LEDs. They have some rather extensive info in some of the data sheets, and app notes, on PCB design regarding heat dissipation. It covers several different board materials, with and without a metal sheet within the board, and plated through vias, open or filled, etc.

Seems to me they use an incredible number of vias to conduct heat to the back side of the board.

JC

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Quote:

Seems to me they use an incredible number of vias to conduct heat to the back side of the board.

One would expect that, as the vias are being used to conduct heat.

If the vias are under the LED it will be a real pain to do the reflow properly. No shortcuts on the preheating. :(

If you think education is expensive, try ignorance.

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I would treat them like QFN packages and add a bunch of small via's on the GND pad for better heat transfer to the bottom plane... You might also consider the use of some small low-profile bolt-on soldered heatsinks on the underside right beside the via's, or over the pads, like this one:

http://search.digikey.com/script...

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Optek makes some that have an even lower thermal resistance (2 C/W), but that's not a huge difference.

You want lots of area on the bottom, just wave-solder it - the mask would act as an insulator.

You want large areas on the bottom, but you also need at least some area on the top as well, and plenty of vias. Use thick copper, 2 ounce or better.

I've done home-made boards with the Opteks and 2-ounce copper, and had very good results.

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Often, aluminum based PCB is used for this power level. Many PCB manufacturers now offer this option for this kind of applications. Although PCB is more expensive, that reduces the size needed of it to dissipate heat, but usually it is preferred to use aluminum as a heat transfer to some heatsink.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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This may be a dumb thought but could a fan be an option? There is no mention in Mike's post on how the heat will be released.

Jim

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Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Quote:
how the heat will be released.

There is enough space inside the plastic of the product, but not enough for the Led Strip PCB. That's why my question had to do only with the Led Strip PCB.

Thank you all guys for your suggestions.

Michael.

Michael.

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You will still need a vented enclosure to let the heat out... Maybe a small fan and a temperature sensor could help you evacuate the heat... Something like this:

http://search.digikey.com/script...

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As Guillem said. Metal clad pcb is a good way to go with things 1W and higher.

Aluminium and copper substrates are available. And even then further heat sinking is often required.

oddbudman