Lower temperatures on your LED chips

Compatherm Paste – the Top Choice for High-Power LED Cooling

Keeping LED’s at a comfortable temperature is tricky business. Let them run too hot, and all kinds of nasty things happen with efficiency, longevity, colour spectrum, etc. But we’ve got you covered!

When designing a new lighting application, there are some things you unfortunately can’t do a whole lot about. The world your shiny new lamp ends up in is the temperature it is. With the amount of light you want shining out of it, the power consumption is pretty much what it is, too – the efficiency of each generation of high-power LED’s gets better, but still – it’s far from 100%.

Between those two; the power consumed by the LED’s – or rather, the portion of that power consumption that doesn’t come out as light – and the temperature outside the lamp, what we call the ambient temperature; there is a delicate balance that needs to be struck.

Get it wrong, and the LED chip gets too hot, meaning that the efficiency goes down even further, the life time gets shortened … in short, you start losing many of the nice benefits of using LED’s in the first place. 

So what is this balance, then?

Well, the power the LED consumes that doesn’t come out as light takes the form of heat being generated inside the component. This heat needs to get out, because if it doesn’t, it’ll start to accumulate – and the level of accumulated heat is what is known as “temperature”. You don’t want it to climb.

This heat will need to find its way into the ambient environment, and at which this heat dissipation can occur is determined by the temperature difference between the  heat source and the ambient – the greater the temperature difference, the more heat will flow.

And this is the balance: depending on how smooth the path for transferring the heat from the component into the ambient can be made, for any given level of heat dissipation – meaning rate of heat being generated in the device – there will be a point of balance where the rate that heat is being dissipated into the ambient matches exactly with the right temperature difference to drive the heat transfer at that same precise rate. Heat will accumulate and the device temperature will rise until it reaches that point, and there the temperature will stabilise – what we call “steady state”.

 

The smaller the difference – the cooler the device

And there is the clincher: “depending on how smooth the path for transferring the heat from the component into the ambient can be made.” The smoother that path can be made, i.e. the lower the thermal resistance can be made, the less of that temperature difference is wasted in different links in the heat transfer chain, and therefore, the smaller the difference between device and ambient temperatures can be – i.e., the cooler the device can run.

One way of reducing the thermal resistance is to increase the area of the heat sink. More area – less resistance. But this is usually another of those design parameters you can’t do all that much about. The maximum size of the heat sink tends to be defined by industrial design considerations, and/or physical limitations. Again, you’ve got what you’ve got.

Another way is to use a fan, but in many lighting applications, that’s a no-go. And even in some very high-power applications such as automotive head lamps and projectors, where forced air or even liquid cooling may be feasible, it can all be for naught if other links in the transfer chain introduce unnecessary resistances.

And here is the critical point: you have the heat source – your LED’s, most likely soldered to an MCPCB substrate for optimal heat dissipation from the LED chip case.

You have a heat sink to communicate the heat into the ambient environment – most likely out of extruded or cast aluminium … or perhaps a more elaborate design, if your challenge is equally elaborate.

But how to connect the two, to make sure you don’t lose more than absolutely necessary of your valuable heat gradient?

The obvious answer is of course that you need a thermal interface material – a TIM – of some sort. But which one?

For the less severe thermal challenges many types of material may be appropriate, but for the most challenging designs, there aren’t many practical alternatives to paste materials. And for manufacturers in this segment, from road lights to automotive head lamps, many significant actors in the lighting industry are turning their heads towards Compatherm Paste.

 

Very good performance

Compatherm Paste range offers very good thermal performance in the class, and a wide range of different materials for a variety of dispensing options, with materials suitable for nozzle dispensing and stencil or silk screen printing.
This means that for any given build with a LED board and a heat sink, testing a Compatherm Paste material between the two is going to be a good step towards lower temperatures on your LED chips.

But by selecting Compatherm, not only do you get access to top-range materials, you also gain access to Nolato’s support structure. Rapid samples are only the beginning; our service level and responsiveness are setting a new standard in the TIM industry.

 

Why not give it a try?

FREE SAMPLES from our full range are available from http://thermalguide.nolato.com. There, you will also find our Interactive Design Guide, a pioneering tool to help you make first-order approximations on material selection.

 

Want to know more?

Jussi Myllyluoma
Technical contact Jussi Myllyluoma +46 73 334 13 02 jussi.myllyluoma@nolato.com

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