Author Topic: Micro porous heatsinks?  (Read 5347 times)

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Offline nctnicoTopic starter

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Micro porous heatsinks?
« on: August 20, 2017, 07:19:02 am »
I have come across a kind of heatsink I have not seen before. The manufacturer claims it works because it is porous and thus has a large surface area.

http://www.farnell.com/datasheets/2198326.pdf
Has anyone used these in a force (fan) cooled application? My gut says the small holes get clogged up with dust.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline alm

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Re: Micro porous heatsinks?
« Reply #1 on: August 20, 2017, 01:47:03 pm »
What kind of unit is w/mk? Is that supposed to be W/mK? Kind of worrying if a heat sink manufacturer / distributor can not even get the figure of merit right.

My guess is that the air flow impedance is so high barely any air will flow through the heat sink unless you have a fan designed for a very high static pressure with a sealed tunnel between fan and heat sink. If anything, it might perform superior to traditional finned heat sinks in very low airflow passive setups where convection is the main source of cooling. But obviously only a well designed tests can determine this, since apparently the manufacturer is unable to provide any technical details.

Online tszaboo

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Re: Micro porous heatsinks?
« Reply #2 on: August 20, 2017, 02:46:04 pm »
Specification said 5-6W/mK thermal conductivity. That is 80 times worse than copper.
It tells, that they dont specify K/W figures for their heatsink.
But here is their appnote:
http://www.amecthermasol.co.uk/datasheets/MPC303025T.pdf

So whoptee doo, it is better than a 2mm thick copper or aliminium heatsink on a BGA. 2mm.
And it can even cool a Geforce2 400 by 10 degrees. No, that is not the geforce 400. That is a video card, which came out in 2000, without any heatsinking.
 

Offline amyk

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Re: Micro porous heatsinks?
« Reply #3 on: August 20, 2017, 03:29:00 pm »
Works OK -> Gets clogged with dust -> Temperature rises -> Parts fail

Being practically impossible to clean, these are essentially designed for forced obolescence.

:--
 
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Offline nctnicoTopic starter

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Re: Micro porous heatsinks?
« Reply #4 on: August 21, 2017, 01:26:24 pm »
Meanwhile I ordered various heatsinks (ceramic and aluminium) and see which one works best. AFAIK ceramic can have a very good thermal conductivity. Many high power (RF) circuits are build on ceramic substrates which are then glued onto heatsinks.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online Ian.M

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Re: Micro porous heatsinks?
« Reply #5 on: August 21, 2017, 01:48:30 pm »
Beryllium Oxide is the 'bees knees' of ceramics for thermal conductivity (which is the only reason its high toxicity risk is tolerated).

From https://www.americanberyllia.com/beryllium-oxide:
Quote
The thermal conductivity of BeO is extremely high in comparison with other ceramics, particularly below 300°C. For comparison, the thermal conductivity of Beryllium Oxide at Room Temperature is 285 W/mK, for copper it is 400 W/mK, for aluminum nitride it is 180 W/mK, and for diamond it is 2000 W/mK.

There's no toxicity warning for the AMEC Thermasol MPC ceramic, so unless they are heavily loading their ceramic with diamond dust*, there is no way it can out-perform a chemically blacked copper heatsink of equal size with the top surface microgrooved to double its surface area.

* In that case they'd be advertising it as a diamond heatsink as it would be crazy not to claim premium materials 
« Last Edit: August 21, 2017, 02:49:03 pm by Ian.M »
 

Online tszaboo

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Re: Micro porous heatsinks?
« Reply #6 on: August 21, 2017, 02:38:30 pm »
I think "good thermal conductivity" means it is better than FR4. Anyway, let us know if you made any testing and how it went.
 

Offline DBecker

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Re: Micro porous heatsinks?
« Reply #7 on: August 21, 2017, 03:44:13 pm »

* In that case they'd be advertising it as a diamond heatsink as it would be crazy not to claim premium materials 


I used to speculate that when aliens came down and took orders for large diamonds, I shouldn't request jewelry.  I should put in an order for a frying pan.  Followed by a windshield.

Diamond heatsinks now have to added to the list.  I wonder how effective fine diamond dust in a sintered matrix would be -- if it would beat copper.  Even a relatively expensive material can be cost effective for die-contact heat spreading.
 

Offline SeanB

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Re: Micro porous heatsinks?
« Reply #8 on: August 21, 2017, 04:32:01 pm »
Would ask the aliens for some high temperature ( at least 150C upper limit) superconductor, preferably in a sheet form, and some monomolecular wire. Superconductor as heat spreader would be a lot better
 

Online tszaboo

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Re: Micro porous heatsinks?
« Reply #9 on: August 21, 2017, 05:04:21 pm »
Diamond heatsinks now have to added to the list.  I wonder how effective fine diamond dust in a sintered matrix would be -- if it would beat copper.  Even a relatively expensive material can be cost effective for die-contact heat spreading.
The very fine industrial diamond is cheap. This heatsink is about 10 gramm, that is 50 carat, and industrial diamond goes for around 0.3-0.5 USD/carat. So about 15 USD, if 100% diamond. But there will be some bonding material. And no, I dont think that they can create a diamond heatsink from a single crystalline.
 

Offline CopperCone

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Re: Micro porous heatsinks?
« Reply #10 on: August 22, 2017, 08:28:35 pm »
Would ask the aliens for some high temperature ( at least 150C upper limit) superconductor, preferably in a sheet form, and some monomolecular wire. Superconductor as heat spreader would be a lot better

mankind is not ready

If size is not an option, I wonder if you can put a electrostatic dust collector. It would be interesting to investigate the clogabiliy of both systems.

It could temporarily reverse air flow and disable the field to vomit dust all over the intake area and hopefully run for a long time. lmfzao. or fire up an incinerator circuit to burn the dust and reduce its volume.

Don't filters drive you insane? You have to constantly think about what filters are clogged or keep schedules and logs of everything. It's like instituting another beurocracy in your home.

unfortunatly dust is sometimes radioactive. what a menace.
« Last Edit: August 22, 2017, 08:35:30 pm by CopperCone »
 

Offline T3sl4co1l

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Re: Micro porous heatsinks?
« Reply #11 on: August 23, 2017, 12:57:59 am »
Diamond heatsinks now have to added to the list.  I wonder how effective fine diamond dust in a sintered matrix would be -- if it would beat copper.  Even a relatively expensive material can be cost effective for die-contact heat spreading.

Nope: just barely not.
https://www.almax-easylab.com/PCD.aspx

PCD is cheap and popular for inserts and coated tools, used to machine hard, nonferrous* materials.

*Iron dissolves carbon when heated, so you can't run high surface feedrates (and thus high point-contact temperatures) with the stuff.  No advantage.  You use carbide for steel: you can turn hardened steel with carbide, curling off red-hot, stringy chips!  ("Carbide" is actually cemented carbide: WC2 powder, "brazed" together with 10% Co.)

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Offline Kleinstein

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Re: Micro porous heatsinks?
« Reply #12 on: August 23, 2017, 04:40:45 pm »
Would ask the aliens for some high temperature ( at least 150C upper limit) superconductor, preferably in a sheet form, and some monomolecular wire. Superconductor as heat spreader would be a lot better

Superconductors are usually poor heat conductors. With the electrons entering the super-conducting state they no longer participate in thermal conduction. There might be an extra heat flow from generating / splitting cooper pairs. But generally the thermal conductivity goes down when going superconducting - so much as using some metals switched between normal and SC state by a magnet to make a kind of thermal switch. Super good thermal conduction is in the superfluid state - but this is very low temperature helium, thus cold enough for most electronics anyway.

At 5-6 W/m/K the porous ceramics would compete with the thermal paste and even stainless steal is about 3 times higher in thermal conductivity.
 

Offline dorin

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Re: Micro porous heatsinks?
« Reply #13 on: August 23, 2017, 05:20:13 pm »
Maybe it's meant for liquid flow?

Otherwise, if it's just meant to be passive the internal cavities do not contribute to cooling surface area in any way, they just decrease the thermal conductivity of the whole thing.
« Last Edit: August 23, 2017, 05:22:16 pm by dorin »
 

Offline T3sl4co1l

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Re: Micro porous heatsinks?
« Reply #14 on: August 23, 2017, 07:26:03 pm »
If you want a high surface area, liquid cooled material, you might try aluminum and copper foam, open cell.  AFAIK, the thermal conductivity and pressure drop is worse than a properly made heatsink.

A similar material can be made from sintering large metal particles, but it's not known for its fluid flow capability; indeed, quite the opposite.  Oilite(R) (sintered bronze, oil impregnated) is famous for its ability to retain liquid.

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Offline Neomys Sapiens

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Re: Micro porous heatsinks?
« Reply #15 on: August 23, 2017, 08:16:42 pm »

At 5-6 W/m/K the porous ceramics would compete with the thermal paste and even stainless steal is about 3 times higher in thermal conductivity.

Tsk, tsk, tsk! Are you really advocating the use of unlawfully obtained materials here?
Especially doubtful, as such 'wares' are generally called 'hot' rather than 'cold'.
 

Offline T3sl4co1l

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Re: Micro porous heatsinks?
« Reply #16 on: August 23, 2017, 08:27:46 pm »
At 5-6 W/m/K the porous ceramics would compete with the thermal paste and even stainless steal is about 3 times higher in thermal conductivity.

Tsk, tsk, tsk! Are you really advocating the use of unlawfully obtained materials here?
Especially doubtful, as such 'wares' are generally called 'hot' rather than 'cold'.

If it's stainless, I guess you can't get caught red-handed at least.

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline nctnicoTopic starter

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Re: Micro porous heatsinks?
« Reply #17 on: September 04, 2017, 10:18:47 pm »
I tried the micro porous heatsinks but they are not doing much.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online tszaboo

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Re: Micro porous heatsinks?
« Reply #18 on: September 05, 2017, 07:05:36 am »
How did you attach it?
 

Offline ChristopherN

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Re: Micro porous heatsinks?
« Reply #19 on: September 05, 2017, 05:58:22 pm »
I ordered some, they come with a 3M pad.

I'll try to test them within the next days.
 


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