Heatsinking Tutoral

My good friend Dave Jones has a tutorial on heatsinking:

YouTube - EEVblog #105 - Electronics Thermal Heatsink Design Tutorial!


Enjoy, Steve

Its nice to have a video, but i think these calculations are more suitable for a text document cheatsheet. The basics are simple enough to make anyone that understands ohms laws understand them too.

The downside for laser designers is having a lot of unknowns we just have to guess, such as the thermal resistance between a LD and an aixiz module, and that between the module and heatsink. Since those depend on fine details of mechanical construction, it is difficult to even give ballpark estimates for those.

I got about 5 minutes in before I couldn't take another second of that voice. What nationality is the guy doing the videos

Benm said:

Its nice to have a video, but i think these calculations are more suitable for a text document cheatsheet. The basics are simple enough to make anyone that understands ohms laws understand them too.

The downside for laser designers is having a lot of unknowns we just have to guess, such as the thermal resistance between a LD and an aixiz module, and that between the module and heatsink. Since those depend on fine details of mechanical construction, it is difficult to even give ballpark estimates for those.

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Even "real" engineers do a lot of guessing. You run the numbers to get a ballpark and determine if the design is feasible, then there's a certain amount of intuition in picking something that will work. Price, physical aspects, availability and other factors come into play.

When it comes to heatsinking, it's hard to overdo it. For a one-off design where a few pennies extra won't break the bank, it's a lot better to over-design it than skimp.

For intermittent use, having a lot of thermal mass will help as much as anything. For long run times, surface area and airflow come into play.

I'm all for over-heatsinking, unless it is in portable applications where its often not that easy to do, or the result would be very bulky to carry around. Most 'heatsinks' that people put into flashlights are just thermal masses and conductors, the flashlight body has to do all the heatsinking work... which it will not do for several watts of electrical power.

For experimental setups its a lot easier to just put something in that is twice the size you calculated - additional benefit is not burning your fingers on transistors etc that operate near the limit of thermal specs

At last, a qualified statement to some key principles of heat-sinking.

This is essential viewing for all those who think that simply set-screwing a module into a HS, or relying on threads alone is enough to make a contact for reasonable thermal transfer.

It's been said before and repeatedly argued against by some, but without complete contact with the use of thermal paste, and taking every opportunity to avoid unnecessary junctions between a laser diode and the ambient air, there is really no point in going to the effort of trying to heat-sink a build.

I've managed to reduce peak temps on my Q6600 @3.6GHz/1.35Vcore by as much as 8 degrees C across all four cores simply by lapping both contact surfaces, which is a huge improvement.

That's just an example of precisely the same principle, just applied in a different field.

Many thanks for the link LSRFAQ.

Gata said:

I got about 5 minutes in before I couldn't take another second of that voice. What nationality is the guy doing the videos

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New Zealand or Australia.

No offence to Dave Jones though, I know how annoyed New Zealanders and Aussies can get when people mistake their accent for the other

bbshamsa said:

It's been said before and repeatedly argued against by some, but without complete contact with the use of thermal paste, and taking every opportunity to avoid unnecessary junctions between a laser diode and the ambient air, there is really no point in going to the effort of trying to heat-sink a build.

I've managed to reduce peak temps on my Q6600 @3.6GHz/1.35Vcore by as much as 8 degrees C across all four cores simply by lapping both contact surfaces, which is a huge improvement.

Click to expand...

I suppose the important thing is to isolate and address the bottle necks in any heat sinking chain. With laser diodes and cpu's, there is one potential bottleneck in contact to the first different material its connected to. The small size and difficult-to-control contact pressure between laser diode and aixiz module is a potential problem, but one that can be partially overcome using thermal pastes, vises for insertion and such.

Most of the DIY heatsink kits i've seen here seem to address the resistance between aixiz and the heatsink quite well provided you use some paste etc., but from flashlight body to ambient is a factor that is seldomly adressed. This is a shame, because in most builds this is the largest thermal resistance by far.