# what to use for a heat sink



## binkstir (Jul 25, 2010)

Can I use any piece of metal as a heat sink for this emitter, such as a small piece of aluminum or tin? Should I use what sort of compound should I attach the emitter to the heatsink?

http://www.dealextreme.com/details.dx/sku.5876

binkstir


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## blasterman (Jul 25, 2010)

Use aluminum. Needs to be at least 1/8 thick and 8 square inches per side.

I have some of those emitters.


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## znomit (Jul 25, 2010)

Since you're at DX already

Thermal glue and heatsink (junk the fan if you want)
http://www.dealextreme.com/details.dx/sku.4579
http://www.dealextreme.com/details.dx/sku.8944


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## binkstir (Jul 25, 2010)

Cool, Thanks guys. Bummer that they are sold out of the little heatsink at dx.

Znomit, I visited some of you builds, cool stuff.

Blasterman, What do you mean my 8 square inches per side?

Something 3inches long by 3inches wide is 9 square inches. And then make it a 1/8 inch thick. Am I understanding this right?

Thanks
lee


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## blasterman (Jul 26, 2010)

The VGA sink linked above won't come close to handling the thermal of that 10watt emitter.

A standard CPU heat sink will likely get too hot to touch unless it's actively cooled. That's how much heat these things put out.


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## Paul Baldwin (Jul 26, 2010)

blasterman said:


> The VGA sink linked above won't come close to handling the thermal of that 10watt emitter.
> 
> A standard CPU heat sink will likely get too hot to touch unless it's actively cooled. That's how much heat these things put out.



What he says! Those star sinks are ok for an xpg-R4 at 900mA but no way I'd be sticking one of those 10 Watters on it. I have run an mc-e @ 10+ Watts on a larger version such as http://www.dabs.com/products/startech-com-chipset-video-card-orb-fan-403H.html but that's a more efficient emitter and keep in mind if the fan stops your led will quickly  I've found this style to work well for passive cooling http://www.satistronics.com/high-po...r-10w20w-and-30w-power-led-90mm30m_p2162.html some pc heatsinks are a very similiar style with even more mass and surface area.


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## znomit (Jul 26, 2010)

What is the end use here?


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## MikeAusC (Jul 26, 2010)

The ability of different metals to conduct away heat varies dramatically.

You would have to use twice the thickness of Aluminium as Copper to be as effective.

Don't use Brass or Steel - they are far worse than Copper.


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## binkstir (Jul 26, 2010)

> What is the end use here?


 
I was thinking about using these as a cool alternative light over my workbench.


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## blasterman (Jul 26, 2010)

> I was thinking about using these as a cool alternative light over my workbench.


 
Covered this many times 

If cheap firepower is what you need, then Bridgelux is the way to go. They are cheaper per lumen, more durable, better color, and you are buying from a reliable Western Supplier (if that matters).

The big Semi emitters are really only useful if you need colors.


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## Nil Einne (Jul 27, 2010)

blasterman said:


> Covered this many times
> 
> If cheap firepower is what you need, then Bridgelux is the way to go. They are cheaper per lumen, more durable, better color, and you are buying from a reliable Western Supplier (if that matters).
> 
> The big Semi emitters are really only useful if you need colors.



For the cheaper per lumen claim, I suspect it depends a lot on where you live and how many you're purchasing. For small projects, I suspect in a number of cases it won't be. For example I don't know if I can convince Newark to ship to me in NZ, but even if I can, it'll likely add at least $10 shipping probably more.

It's difficult to know how bright the cheap Chinese LEDs are since I haven't seen any independent testing but they claim 600-700 lumens for the 10W one so if we presume it is at least capable of the 400 lumen that the BXRA-C0360-00000 one is it costs US$14.90 minimum vs US$8.88 for one of those 10W ones from eBay. And if I'm forced to buy from Farnell in NZ which I suspect is more likely they charge NZ$13.35 + NZ$14.95 (shipping) = NZ$28.30 or US$20.85 (that's actually excluding GST which I'll have to pay from a NZ supplier but it isn't fair to include that). Cheaper per lumen? Seems not...

Even if I want 2, 2*13.35+14.95=NZ$41.65 or ~US$30.90 compared to US$17 for 2 of the 10 watts from eBay.

Heck even if I go to 6, for which I can get free shipping from Farnell NZ because the order is over $75, it'll be NZ$80.10 or US$59.02 vs US$52.2 for 6 of the 10W from Satisled shipped. However this last comparison is a bit more suspect since I may be able to get the Bridgelux for cheaper from elsewhere since when ordering that many shipping because less of a component (although the 10W may also be cheaper elsewhere). Given the small price difference it may seem worth it to go with the Bridgelux given the other advantages but it remains a fact it's not necessarily cheaper per lumen.

I obviously haven't looked at alternative suppliers (although I have my doubts I'll find anything much better, it's usually difficult to compete on price for such small quantities with HK/China vendors given the price of shipping and NZ doesn't have much of a market for these sort of things anyway). And there may be other options, like an XP-G or P7 or MC-E which will be better. A lot depends on what the cheap Chinese LEDs output which as I've said I've never really seen tested. If they do 500-600 lumens we should be comparing to the BXRA-C0402-00000 or something else. Don't get me wrong, clearly considering other options like Bridgelux is a wise choice, I just don't like blanket statements which IMHO are probably not always true and claims like 'cheaper per lumen' are the sort of thing which does tend to vary a lot on the quantities you're ordering and where you live.

For very large quantities (I'm thinking in the order of 20k at a minimum) it wouldn't surprise me if the Chinese LEDs came out better too. Because realisticly, competing on cost is the only way they can survive (as it is with many Chinese manufacturers) and they seem to be surviving fine. And I doubt small order are the reason for that. For someone buying 10k, they'll have to be stupid not to do some independent testing so they will have a good idea of what's cheaper per lumen. Of course they won't be asking on CPF either but I think it's another reminder to be careful of blanket claims.

Chinese manufacturers also have the advantage that they often ignore patents. While buying from such manufacturers seems ethically questionable, if you're looking at it solely from a cost and efficiency viewpoint it means they don't tend to be that far behind the curve even with their often minimal research.


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## Paul Baldwin (Jul 27, 2010)

binkstir said:


> I was thinking about using these as a cool alternative light over my workbench.



You may be better off using more leds for a workbench light. One large led will provide plenty of light but you will end up with heavy shadows, not what you want for marking up, precision cutting etc.
I made a worklight for a friend using xpg R4's. As it was designed to be portable there was a limit to how large he wanted it so I had to strike a balance between size and quality of light. I ended up with this that I hashed together last New Years Eve https://www.candlepowerforums.com/threads/255712&highlight=worklight
The white light is great to work under  a number of people have commented on that with no prompting from me. We ended up using it the other week as the shearer got delayed, started at 10.30 pm, I didn't see him nick one sheep with the shears and he asked where we got it from.
The output from 4 neutral xpg R4's @ 900mA would be ample for any wokbench imo.


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## IMSabbel (Jul 27, 2010)

blasterman said:


> The VGA sink linked above won't come close to handling the thermal of that 10watt emitter.
> 
> A standard CPU heat sink will likely get too hot to touch unless it's actively cooled. That's how much heat these things put out.



You guys are totally pampering your LEDs. A heatsink temperature of 55-60C will still keep the LED die in spec for most LEDs.
This can feel "burning hot" when touching, but nothing wrong with it. 

And well, they dont put out that much heat. I can tell you that its less than 10W. Which is not that much. You can dump about 20-40W with a CPU heasink without a fan, with a CPU. Leds are less sensitive. A good-size heatpipe CPU cooler will run 4 SST-P7 at 3.5A indefinitely...


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## Paul Baldwin (Jul 27, 2010)

IMSabbel said:


> You guys are totally pampering your LEDs. A heatsink temperature of 55-60C will still keep the LED die in spec for most LEDs.
> This can feel "burning hot" when touching, but nothing wrong with it.



Fair comment I suppose, they'll still work. Personally I can't see the point in spouting about the longevity aspect of leds to people, building something and then having it fail when it goes outside the usual circumstances. I've tested the worklight in my inglenook fireplace at well over 30 degs C for hours, no problems and no appreciable lightloss. I've also used it on tomato seedlings for 18 hours a day, just to see what happens, again, no problem. If temperature effects the lumens output I think it defeats the object of the excercise to use an inadequate sink.


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## blasterman (Jul 27, 2010)

> I just don't like blanket statements which IMHO are probably not always true and claims like 'cheaper per lumen'


 
I actually have one of these emitters, along with a one of a kind royal blue version I had made custom. First, while I haven't formally tested it, I'm pretty sure the 10watt Chinese *isn't even as bright* as my 5watt Bridgelux 402s. The Chinese have never been honest about the lumen value of any of their emitters, but I do trust my eyes and specs given by Bridgelux and Cree.

Newark doesn't even charge me shipping in the States for small orders, so an $11.30 10watt Chinese emitter from DX doesn't compete well with a 5watt $6.75 Bridgelux that's puts out at least the same lumens and has reputable specs. I also stated that the color of the Chinese emitter is terrible and old gen - much like cool-white Luxeons and not good to work under because of the lack of longer wavelengths. The Bridgelux is as good as any Cree at 5600k.

Obviously from NZ, or a country where hefty import over-head applies the economics may be different. Cutter for instance is a great company to buy from, but in the U.S. the improved efficiency of the XPG often gets trumped by the superior horsepower and distribution channels of Bridgelux. So, I'm not disagreeing with you a bit on your local economics.

However, I clearly stated my comparison was based on Western sources, and the vast majority of inquiries we get consistently about this emitter are from people whothink DX and Ebay are the default bargain sites of the universe and too lazy to do the math. I find it funny that I can get this emitter about 40% less than DX anyways. As it is, if they were free, I still woudn't use them. I give it a week before somebody starts yet another thread asking about the 50watt version on Ebay and why they aren't revolutionizing the lighting industry :shakehead




> Chinese manufacturers also have the advantage that they often ignore patents.


 
That's rather offensive stated in a technical forum, and in that respect I'd prefer not to help you on this. I have some really great designs on the board right now from some killer lamps, but am holding off simply because they will be ripped off the Chinese the second I put them on a commercial web-site. 



> You guys are totally pampering your LEDs. A heatsink temperature of 55-60C will still keep the LED die in spec for most LEDs.


 
These Chinese LEDs are notoriously sensitive to high thermal, and Vf anywhere near over spec. I've burnt a lot of them up where Crees do fine, so if you want them to last awhile you'll want to stay with generous heatsinks.


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## IMSabbel (Aug 2, 2010)

Guess that is fair.
Although this can really eat up the cost difference: A fancy heatsink can have a non-trivial impact in the total cost of ownership of a LED device, even for fixed lighting with long "on" cyles.


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## Ken_McE (Aug 2, 2010)

IMSabbel said:


> ... A fancy heatsink can have a non-trivial impact in the total cost of ownership of a LED device,



That's why we use long strips of Copper or Aluminum that we buy in any hardware store. The manufacturer labels it as a "waterpipe" or "carpet trim strip", or "roof flashing" but those labels come right off.


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## nein166 (Aug 4, 2010)

Here is an example of a heatsink handling 10w passively
The heatsink is from an old AMD 939 socket
The MC-E is on a star, independent DX drivers for each die





After 30min the heatsink is hot but not painful to touch
It was designed to handle 100w with a fan


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## jason 77 (Aug 4, 2010)

nein166 said:


> DX drivers for each die



HAHA! hard drive magnet used as a tool holder, I do that too!


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