# How big of a heat sink do I need for these LEDs?

#### -live wire-

Joined Dec 22, 2017
901

#### -live wire-

Joined Dec 22, 2017
901
I will probably use constant current, not a resistor. But since the end goal is RGB for more stuff and an RGBW flashlight, the fan shouldn't be too big or consume more than .5 watts.

#### -live wire-

Joined Dec 22, 2017
901
thats not a heat sink, its a spreader

Joined Mar 10, 2018
3,785
Is there a good way to estimate the required heatsink size?
What I posted was the methodology on how to get to a heat sink size.

It depends on a number of variables, air flow, thermal mass, heat flux
that has to be removed.......

Its like getting open heart surgery, not done winging it if you want reliable
solid design results.

Youtube and some of the heatsink vendors have training videos, that may
lend a guiding hand to your effort.

Regards, Dana.

#### oz93666

Joined Sep 7, 2010
724
This doesn't seem a very convenient way to do what you want .... this is the way a manufacturer buys them , then put them on a spreader , or in completed products ... you are going to find soldering very fiddly , and applying thermal compound messy on that small area....

You need to consider the end product , are these going to be all in one tight location ?? tricky for dissipating the heat .... you cannot allow the eye to see directly the light source , this will leave after image effects in the eye and is very unsatisfactory ... the light must bounce off a wall or ceiling first ....

Much better put those leds away in a cupboard and buy some like this ....

Self adhesive RGB strips , each chip is around 20 to 100mW so no head build up or heat-sink. but with many per meter you get plenty of light output .... many different types , very cheap , some with remote , see eBay ... some consume 30W/meter , some , like the strip pictured alternate RGB with white

Even these low power leds are not comfortable to look at directly ... this arrangement is best ...

The spreader mvas linked to is what you need for the leds you have ... then some thermal compound ... THEN you need a heat sink of some type ...at the end you will spend a fortune , and the result will look a mess .... Don't go down this route !!!

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#### -live wire-

Joined Dec 22, 2017
901
I am thinking of using them in a flashlight or in a PC, not for lighting a room. So is there any good rule of thumb or way to estimate a good heatsink size for the LEDs I have? Maybe that will involve getting a slightly larger heatsink to be safe? There isn't any datasheet containing details on the exact thermal properties.

#### BobTPH

Joined Jun 5, 2013
2,198
If you can buy the same already soldered to the stars it would be a good start. And again, those are not the heat sink, they are the interface to the heat sink.

That said, if you run them at about 1/4 power (1W total max) the star itself might be enough heat sinking. I have used them this way without problems.

For a little more heat sinking, the star can be fastened to the computer case.

Bob

#### oz93666

Joined Sep 7, 2010
724
I am thinking of using them in a flashlight or in a PC,.
This would be better for a flashlight .... 100W

And a collimator and lens ... .... dozens of different heat sinks , fan assisted would be best