LED Heatsinks? - Page 1
Forum section: electronics / projects

author: AcHmed99
author_rank: Contributor
timestamp: January 27, 2014, 09:07:59 pm
content: I was looking for some heatsinks for some Bridgelux Vero10 LED's and came acrossthese. Newark's description doesn't match the datsheet specs for 50mm the datasheet says thermal resistance is about 1.75. This seems a little optimistic for a relatively small and cheap heatsink. Then the way heatsink prices are has always baffled me there never seems to be a correlation between thermal resistance and price. Anyways has anyone tried any FISCHER ELEKTRONIK SK 46 series of heatsink?Here for example is a2.76 thermal resistance heatsink. I have some of the OS512 series and they are definetly beefy what you would expect for relatively low thermal resistance. What is FISCHER ELEKTRONIK using some new material or discovered some radically efficient design that they can sell for so cheap?

author: M. András
author_rank: Super Contributor
timestamp: January 27, 2014, 09:28:09 pm
content: look at therehttp://www.led-heatsink.com/its a shame btw that none of the well known distributors stock these vero arrays in europe or for a ridicoulus price in extreme quantities

author: phil
author_rank: Regular Contributor
timestamp: January 27, 2014, 09:31:31 pm
content: Fischer is a reputable german heat sink manufacturer. These star hear sinks are just slices of a large aluminium profile, thats why they are so cheap. I used quite a few of them in the past and they performed well. I never did any real measurements, but you could still touch the heat sink with a 5W CREE LED. They were only 10mm thick, so a fair bit thinner than the ones you linked. Also, they were bare aluminium. I think 4-5°C/W is realistic for the 10mm type. They are about 1.50€ each. (and ~1€ for 50+)~2-3°C/W for the 20mm type sounds reasonable to me.Phil

author: Corporate666
author_rank: Unknown
timestamp: January 27, 2014, 09:51:30 pm
content: Quote from: M. András on January 27, 2014, 09:28:09 pmOhh, awesome link! Thanks!BTW, I bought a bunch of the Vero LED's and they are absolutely awesome. I compared them against the Cree and other COB LED's and when you take into account the CRI bins, the Vero's were the hands down winner for price/performance. The other nice thing is you can actually buy the high-CRI Bridgelux LED's. I've only ever found the lower CRI Cree's. Actually, that seems to be a problem with Cree in general... they have so many bins and order codes, but all that is in stock anywhere is the lower flux, lower CRI stuff.

author: M. András
author_rank: Super Contributor
timestamp: January 28, 2014, 08:25:22 pm
content: Quote from: Corporate666 on January 27, 2014, 09:51:30 pmthese arrays are in the top efficacy class atm. but ffs why do i have to pay half the price of the 10k lumen neutral one for get the led from farnell. they only stock it in their american warehouse....AcHmed99:1k lumen is pretty bright if i remember right the 100w incadesence is around 1600lumen total. the led emits around 115 and 130degrees from its base its damn brighti made this little panel with 14 luxeon rebel leds these ones mounted supposed to be 160lumens each at 700ma drive current. they pretty damn bright and heats up quickly, f***d up the thermal plane in the middle either too few vias already there is 150 in staggered row configuration or too small diamater ive used 0.5mm vias on 1oz copper with an 1.6mm fr4 had to solder the bottom 2 mounting holes trough into the aluminium heatsink to bring the leds base to 50celsius at 700ma drive. i wonder btw if tripled amount of vias would be good as i dont like the perforated example design for these leds 30+ vias at the base of the led... or would be simply solved by an aluminium core pcb. but i would simply wticht to 1 of those vero arrays instead as these small leds whati have only 76lumen/w and the vero arrays are at 110+. make another batch of these boards would not worth for me as i didnt paid more for 50 of these leds then for the 10pcs 10x5cm boardssorry for the pciture quality taken by a 6300 in low light conditions as i couldnt find the digital camera when i took the picture

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 29, 2014, 03:46:01 am
content: You can use thermal epoxy or even JB Weld.

author: Corporate666
author_rank: Unknown
timestamp: January 29, 2014, 04:39:12 am
content: Quote from: AcHmed99 on January 28, 2014, 02:18:25 amI got some Vero 10, Vero 13 and Vero 18. Personally, I would not bother with the 90/97 CRI ones, certainly not for a garage. I got some of the 80, some 90 and some 97 CRI. My office lighting is all 5000k 90CRI daylight fluorescent which I have gotten used to. The 3000k Vero @ 97CRI have a very nice color, but it's yellower than I prefer. The higher color temps still have good CRI and you lose a lot of lumens to get the 97 CRI. I am driving them direct-DC but so far have just had them hooked up to my bench supply. I also bought some Recom drivers which will run them, but I am going to build my own boost driver and run them from something like a 24V DC wall adapter.I haven't tested the light output but I definitely think they are putting out their rated lumens. Just be sure to read the datasheet and not just the marketing hypeThe marketing hype will brag about efficacy and lumen output, but then you notice that when you get the 2700K model and 90CRI you are nowhere near the numbers they claim (which are for cool white, low CRI versions). I think my Vero 10's are in the 600-700 lumen range at 10W of drive power. You can run them harder but the efficiency drops and it's just more heat.

author: Corporate666
author_rank: Unknown
timestamp: January 29, 2014, 04:50:45 am
content: Quote from: M. András on January 28, 2014, 08:25:22 pmPhilips/Lumileds has a really neat application note about PCB thermal performance. Cree also has a cool app note about the same thing but focusing on via size and placement. They show how the right combination of board details can actually get you a lower thermal resistance than a MCPCB (if you believe their data). A few things I remember... 0.8mm PCB's have drastically lower thermal resistance than 1.6mm PCB's. Vias are only effective close to the heat pad of the device... once you get 5-10mm from the heat pad, the heat has already spread out enough that thermal vias lose almost all their effectiveness. Also, "filled and capped" vias with thermally conductive epoxy (or pure copper) is recommended, but I have never found a PCB shop that does such stuff - I've only seen traditional filled/capped vias. But, a good alternative is filling the vias with solder - provided you get good fill all the way through (you need to choose the right size to get the solder to reliably wick in and fill the gaps).One LED I have been playing around with which I really like is the Samsung LM561B (I believe is the PN). They produce over 170 lumens per watt at If of 65mA. And at 65mA they will produce 25 lumens. They are so efficient that they often don't need a heatsink, even in bulk on a PCB. Samsung sells some small board - maybe 2cm x 5cm with 5 on the board, and it doesn't require a heat-sink at all. You can also pack them in much more densely and run with a heatsink.I had the Arrow rep in a few weeks back and Samsung has just released a 90CRI version of this LED which is still equally efficient as the existing one - amazing. They are usually used in side-light applications but they are cheap - $0.10/ea and so efficient that you can toss a bunch of 'em on a board and get great quality and quantity of light for not much $$ or heat.

author: M. András
author_rank: Super Contributor
timestamp: January 29, 2014, 06:32:01 pm
content: Quote from: Corporate666 on January 29, 2014, 04:50:45 amive read those papers. the top copper flood conducts the heat pretty well. but its not getting to the otherside of the pcb and a 0.8mm pcb didnt seem to enough durable to mount them with screw in such a large area with thermal paste between the pcb and the heatsink, oh and i dont remember if its fall into the extra fee category or not but that was the other factor, seed and iteadbut i would still love to get 1 of those vero arrays from european stock but found none yet