Heat sink for 3 watt LEDs

[LED-high]

Hello.

I'm about to start my old hobby of electronics design! One of my projects include using 3 watt LEDs, the Luxeon I & III star to be more precise. I understand that I need a heatsink for this LED but my question is which I should use. When I talked to some guys where I bought the LEDs they said I needed a heat sink that costs more then the LED itself! This does not sound reonable to me, so I decided to searh the Internet!

I came across this page that had a few heat sinks for sale CLICK HERE

The prices range from ~€1 to ~€8, but which would you suggest?

The LEDs will be used as extar light and willmost likelybe on about 12 hours a day. The space around the LEDs / heat sink will be movin air, I'm thinking about installing a fan if needed.

If I mount the LEDs on a aluminum plate (rughly 2x2 in), would this be enough of a heatsink?

The guys at the store also talked about the need for using screws with the heat sink, is this needed or would thermal adhesive be enough? There are two adhesivs at the shop, a
Two-component glue and a thermal compound would you recomend any of these?

 

[yellow]

Luxes make just half the light but double the heat than modern Cree/Seoul led, so You would need a larger sink for them
Try to find some place where old computers are trashed and get the sinks of some Pentium II, f.e.
They are huge and - if You are lucky - "cost" only the time to remove them.
Alum. plates can also be used, 2" x 2" x some mm should be enough, You can simply grip test after a few mins of use
(when You burn Your fingers, there was not enough material and/or moving air)

With led mounted on stars, using screw to attach the stars to the sink is simply the best way. Also the led are removable, You can upgrade to other led with ease.

I would advise to skip the expensive "thermal glue".
You have to use "thermal paste" on the backside of the star - push on them and "workt them in" to get the paste as thin as possible - then use the screws to fix the led.
Instead of screws, You could glue the led in with epoxy glue around the Star (but the screws are better)

 

[LED-high]

Thank you for the answer...

Which heat sinks would you recomend for the 3 watts, and do they have pre-drilled holes for the screws? I just happen to have access to heat sinks made for CPU's that I could use for the stars, they are also equiped with a fan that could be used to cool even furter.

I understand that I would get the LEDs closer to the heat sink and have better removal of the heat from the LED. I just don't see how I will be able to use screews if the heat sinks don't have the screew holes when I buy them. I don't have accesss to a drill that would have the capability to drill the holes needed.

I could drill holes on plates though, how big would the plates have to be to function as a heat sink?

 

[Mr_Light]

This thread will give you an idea how big an aluminum plate you would need for your LEDs.

http://www.candlepowerforums.com/vb/showthread.php?t=226508

I have used the following thermal glue to attach hundreds of leds to heatsinks without problems.
FUJIK Silicone Thermal Glue (50ml Grease-Like)
Price: $7.77
http://www.dealextreme.com/details.dx/sku.4579

and while you are at it, these CREE LEDs will be about twice as bright as your Luxeon LEDs for the same amount of current.

Cree XR-E Q2 Emitter with Star
Price: $4.13
http://www.dealextreme.com/details.dx/sku.2395

 

[LED-high]

and while you are at it, these CREE LEDs will be about twice as bright as your Luxeon LEDs for the same amount of current.

Cree XR-E Q2 Emitter with Star
Price: $4.13
http://www.dealextreme.com/details.dx/sku.2395

Than you for the links, I know that there are LEDs out there which are better. The problem is that I need specific a LED at 450 (+/- 10 nm), that is why I'm using the Luxeon 3W LED. I you know of any HP-LEDs that have this wave lenght please let me know.

I have made a design for a heat sink that will be given to a mechanical engineer for a price estimate. The plate will be roughly 3 mm and have 5 grooves (striations?) 1 inch high to disperse the heat. Do you guys think this could do it? It will be made in aluminum and painted black.

Sorry for missing some letters when I type, I'm using a small keyboard :sick2:

 

[mds82]

i would check Digikey for heatsinks - they have a LOT of options

http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1179752&keywords=heatsink

 

[LED-high]

i would check Digikey for heatsinks - they have a LOT of options

http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1179752&keywords=heatsink

That looks like a really good page! But which parameters would I use for the LEDs I'm using? :thinking:

 

[Garibaldi]

Ledengin makes a 455-465nm "Dental blue" LED that might work for you. They don't make the 3W versions any more but make 5W and up now. They recommend the Cooler Master 50x15mm black heat sinks for the 5W versions which have a thermal pad and are pre-drilled for screws, with mounting screws included.

 

[lolzertank]

Than you for the links, I know that there are LEDs out there which are better. The problem is that I need specific a LED at 450 (+/- 10 nm), that is why I'm using the Luxeon 3W LED. I you know of any HP-LEDs that have this wave lenght please let me know.

The royal blue Luxeon Rebel satisfies all these requirements. If you can get the highest bin that produces 425mw at 350ma (good luck, you will need to call or email Future Electronics), the efficiency is about double the Luxeon III's.

Alternately, if you could increase your tolerance by 5nm, you could use the Cree royal blue XR-Es.

 

[mds82]

That looks like a really good page! But which parameters would I use for the LEDs I'm using? :thinking:

you can search by what ever size requirements you need, this way you dont need to build a custom heatsink. the size heatsink will be determined by how many LEd's you use, and how much current you drive them at.

 

[yellow]

sure, the best were when You could drill Your own holes, suitable to where the Stars will be located.
Usually this means drilling a slightly smaller hole and then cut threads.

But when You come from the computer side, You will surely have noticed there are screws with wide threads that are forced into threadless "holes".
just do the same, get some of such screws and drill a hole just as small to have the threads engage. Here we would call such screws something like "wood screws".
... or use some glue, whatever You want.

Those small computer sinks, wide enough to house a small fan, were perfect - I got mine totally for free from some Computer Junkyard. But I think You wont need the fans at all.

 

[LED-high]

I appriciate all the help you guys have given me. what would you say about this cooler with fan for my project? Snowflake cooler w. fan

Some unknown guy makes a statement that he has used this fan for cooling of a Cree Q5, would it suit my need with the Luxeon?

While we are on the subject of LED I think it could be a good idea for me to continue the quetioning on the subject! I think that the LZ1-10B205 (LedEngin) would suit my needs even better at an afordable price. If I use this led could I use the cooler mentioned above to keep my LED cool and save it from overheating? Or should I use a bigger one like this? 3.15x2.76 in

 

[mds82]

Newegg.com would be much better for buying a heatsink -
http://www.newegg.com/Product/Product.aspx?Item=N82E16835103155

i would check that out or something similar

even a VGA cooler - http://www.newegg.com/Product/Product.aspx?Item=N82E16835119080

 

[Garibaldi]

Either of the active heat sinks you're looking at should be fine for the LZ1-10B205. The recommended heat sink for these are the passive ones here http://www.mouser.com/Search/ProductDetail.aspx?qs=2%2frW%252bE6BnutUSws9Jmtieg%3d%3d

I can tell you that even after several hours, they barely get warm. Plus, they come with the thermal pad and screws. If you're going to have them in an enclosed location, active cooling might be needed, but if they're in open air, just the heat sink is all that's needed.

 

[Bronx68]

Does that mean you don't need any thermal grease since thermal pad???

 

[alpg88]

Thank you for the answer...

Which heat sinks would you recomend for the 3 watts, and do they have pre-drilled holes for the screws? I just happen to have access to heat sinks made for CPU's that I could use for the stars, they are also equiped with a fan that could be used to cool even furter.

I understand that I would get the LEDs closer to the heat sink and have better removal of the heat from the LED. I just don't see how I will be able to use screews if the heat sinks don't have the screew holes when I buy them. I don't have accesss to a drill that would have the capability to drill the holes needed.

I could drill holes on plates though, how big would the plates have to be to function as a heat sink?

cpu heat sinks will work just fine, especially with fans. i had p7 (10w) cpu heatsink, no fans , it was about 3x3, and it worked just fine,

snowflake looks like more than enough for 3w, you'll need to drill holes and turn the thread, for securing stars, or if you have just emitters, even easier, just glue them to the sink with thermal epoxy.

or you can do things a lot simpler and easier, instead of buying fans with heat sinks, get yourself mr16 with cree leds, and be done with it.

 

[deadrx7conv]

http://www.satistronics.com/Wholesale-led-lamp-lightings-heatsinks-for-led_c1027

If you look on ebay and search for LED heatsink or LED heat sink, you'll see various types. It'll give you an idea what size you need for your project.

Find discarded computers as there are many square and round heatsinks cooling those CPU/GPU/northbridges/VGAs.... Even a Pentium 1 or AMD k6-2 or K6-III heatsink should be plenty for a 3-5w LED without needing the fan.

The Snowflake should be fine with the fan. And, if it is in an open area, you can use the 'touch' test to see if it overheats without the fan.

 

[Paul Baldwin]

I've used the snowflakes with fans removed and a driver epoxied in its place with no problems. That is with Cree XPG-R4's however so heat is less of a problem I'm sure. I have run them for up to 18 hours a day and tested them to an ambient temperature of over 30 deg C.

 

[Oznog]

An unfinned, 2" x 2" block of aluminum will get QUITE hot with 3W used. That's a problem for something left on continuously.

There are good thermal epoxies out there. Arctic Silver is VERY good.

The MCPCB ("star", "snowflake") boards are great because the thermal pad mounting is so critical. In many cases thermal epoxy is simply not good enough when moving all the heat across that tiny area, esp if you're not skilled at applying it. Also, many emitters have non-neutral thermal pads, which might create major problems if connected to a grounded heatsink (some drivers isolate so it won't be a problem, or allow a grounded terminal. Also all the MCPCB boards electrically isolate the thermal pad so it won't matter if it's neutral or not).

 

[bstumm]

You can get a pure copper, bonded fin, 2U Server CPU cooler with side blow fan for about $20. This heat sink can handle 6 stars at 10W easily (10 degree C rise).