Heatsinking with non-metals?

[HumanSymphony]

what kind of non-metal heatsink stuff is there?

 

[styropyro]

Beryllium Oxide is a great heatsinking material that doesn't conduct electricity.

 

[diachi]

That white thermal compound glue stuff

 

[HumanSymphony]

is it safe to entirely cover a driver with? possible board damage?

 

[GamerBR]

What you can do is make a heatsink with aluminum or copper for the driver that ALMOST touches it,than the rest you fill with non conductive thermal paste,like arctic silver ceramique(or even arctic silver 5,it's non condutive,but it's better not risking it).

 

[HumanSymphony]

hmm i can't really just MAKE a heatsink dude. I was thinking more along the lines of just a big glob of thermal paste... lol might be able to macgyver myself a heatsink out of aluminum foil or something.

 

[GamerBR]

I have my doubts if that would work better than nothing,even with high grades thermal pastes like Arctic Silver Ceramique :-/

 

[HumanSymphony]

well...... crap

 

[pullbangdead]

Thermal conductivity without electrical conductivity, tough to do.

How does heat move through a material?

Well, the most common is through electron transport, hot electrons diffusing into cold areas. This is what metals use, since they have a sea of electrons that can all move. The catch there? Yep, electrons moving means electrical conductivity as well as thermal.

What's the next most common? Phonon transport. A phonon is a lattice vibration, but it can travel through interconnected networks, such as an atomic lattice. Temperature is average kinetic energy of all the atoms in a solid, and that kinetic energy is in the form of each atom vibrating in it's slot. Imagine a bar of, say, diamond, which doesn't conduct electrons. Now say one side is hotter than the other. Which means the atoms on that side are vibrating at higher energy and amplitude. Since all the atoms are connected together in a network, that vibration can be transferred through the material to the atoms that are colder, and eventually, all the atoms will be vibrating at the same energy/frequency. The action of that vibration moving through a solid mimics that of a particle moving through the material, and that imaginary particle is called a phonon. (Another visual aid: imagine a huge 3-D networks of spheres all connected to their neighbors with springs, forming cubes. Now, thump one of those spheres, and observe the vibration moving through the network. That is a phonon.)

So, you need good phonon transport. Turns out, any imperfection in a material will inhibit phonon transport. Grain boundaries, dislocations, everything. Things will still transport phonons, but not very efficiently. So it's really hard to do. When using paste or something like that, you still have to rely on the vibrations of atoms, but the less perfect a network is, the worse is it.

For something like Arctic silver, they put actual silver in the paste. The heat can move through the small bits of metal in the paste, but can't overall conduct because the electrons can't jump from one silver particle to the next. But the charge will still move within the particles, and having this charge in there and having it close to electrical vias and paths, the paste can act in a capacitive fashion, which can screw with the electrical components even if it won't conduct and act like a short.

There is one other big way that heat can conduct, but surely we all know that one, given the kind of forum we're all on.

 

[brtaman]

Well there is always diamond IIRC around 4x as thermally conductive as copper (silver is a tiny bit better than copper).

Hehe, now that would be a "pimp" laser, you could cut out the host to show of tha bling heatsink ;D

If you're looking for a tiny heatsink for your driver, check out my thread http://www.laserpointerforums.com/forums/YaBB.pl?num=1216138225 there is a picture of a heatsink I put on the driver. I have some of this heatsink left over, so if you were to give me some measurements I could see what could be done and send it your way if it would help?


Thanks
brtaman

 

[HumanSymphony]

it would be for a rkcstr driver

 

[rkcstr]

Could just ask me  ;D

Here's something I did once:

It's just aluminum channel stock from Lowe's, cut to length and mounted between the board and chip.  It took a little work to make sure it didn't short against the chip legs or nearby pads.  It was my old style driver too, so I'm not sure what it would take for my driver now, which is slightly different.  If you need to fit it in something, you can cut the fins down as well.  Just make sure it doesn't touch a grounded case as it is tied to the output pin of the regulator IC.

As performance goes, here's a graph of the different temps over time, bottom one is the driver with a heatsink, top two are two different attempts with no heatsink with #2 being a better representation of what to expect with no heatsink.  This was at 400mA output, with ~6.5V input voltage and ~3V output.

 

[MarioMaster]

as good as heatsink paste is at helping heat conduction between two surfaes, when you start piling it on it quickly becomes an insulator - when you use it on two flat surfaces you're only dealing with a very thin covering

just dunking something in heatsink paste is a bad idea as it conducts heat a lot less than say copper or aluminum

 

[brtaman]

Yeah I am pretty sure I have that much heatsink leftover, you dont need it for the whole driver though. Just the IC like rckstr did. I'm gonna go check, if its there I can send it your way np.


brtaman

 

[pseudolobster]

Well there is always diamond IIRC around 4x as thermally conductive as copper (silver is a tiny bit better than copper)....

Beat me to it....

Diamond has among the highest thermal conductivity of any material, some 6x higher than silver... It's also nonmetallic and not electrically conductive.
here is a review of some commercial diamond thermal grease,
and here is how you can make your own for cheap (much cheaper than you think)

 

[HumanSymphony]

Yeah I am pretty sure I have that much heatsink leftover, you dont need it for the whole driver though. Just the IC like rckstr did. I'm gonna go check, if its there I can send it your way np.


brtaman

cool let me know ;D