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crazy idea about cooling transistors

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Marko

Thu Feb 16 2006, 06:51PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Well I drilled sides carefully, inserted and soldered two small resistor-holder tubes.
Transistor is undamaged and fully operational (OK I used old junk, didnt want to torture even 2N3055s

, but this one survived drilling)
Soldering may be ugly but I did this in few minutes and didnt bother for much.

Now distilled water can be flowed trough transistor (maybe oil or some other liquid for higher voltages) in order to get it rid of heat.

As It sweeps around silicone it can carry out extensive amounts of heat, far better and faster than any outside-case cooling.
As water heats up is can go in some forced air cooler or something like that, or just big reservoir that dissipates heat by its surface.

Small pump is needed to circulate water, and it can do for lots of transistors...

Sulaiman

Thu Feb 16 2006, 06:56PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

One important reason for transistors being in seled packages is
to keep out humidity!

Humidity (with heat) will quickly corode the metalisation away - ruining the device.

Marko

Thu Feb 16 2006, 07:06PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

yep.
Thats why water must be inside all the time and disstiled, in order not to corode the transistor (may be tricky) or just oil can be used as well.

If air is let inside it will corode fast, so it must not be 'watered and dried' all the time.
If there is no oxygen it cannot corode, and as water is distilled it cannot form galvanic currents and eat the transistor.

In bare air without water people operated such transistors well, so 'no-case' is not a big problem.

Im wondering what else instead of mineral oil and water can be used, in order to make good dissipation and not to cause corrosion ..

HV Enthusiast

Thu Feb 16 2006, 08:18PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

wrote ...

As It sweeps around silicone it can carry out extensive amounts of heat, far better and faster than any outside-case cooling.
As water heats up is can go in some forced air cooler or something like that, or just big reservoir that dissipates heat by its surface.

Even with chilled water, i seriously doubt this solution we be as effective as attaching the device to an air cooled heatsink. You are assuming that the primary path for heat will be on the upper side of the device (where you drilled your hole), when in fact path of least thermal resistance is likely on the bottom of the device where the can mates with a heatsink. Also, merely passing a tube through the device is going to be very poor at removing heat. You really need to have some turbulent flow inside the device to get good heat conduction.

The idea you are proposing obviously is quite involved requiring careful machining of the said device (which in itself is not a good thing) and a complex liquid cooling scheme. Without a doubt, you will cool the device much better (and simpler) with just a simple air cooled heatsink. Just think surface area for starters.

If you are going to go through the trouble of designing a liquid cooled apparatus, then how about a liquid cooled coldplate to attach the devices directly to. This will be far superior than attempting to cool the package by drilling a hole and feeding a tube through it.

Anyways, you said it in the title, "Crazy!"

Marko

Thu Feb 16 2006, 08:34PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Well, il give it some tests, maybe, and tansistor will be heatsinked if needed.
But you must consider space taken by water cooled heatsink, I intended this to be compact (if possible).

Here water contacts silicon from all directions, maybe mistake is no turblence but doesnt matter a lot now.

The point is to make system smallest possible, and try not to use heatsink...

ell some crazyness is always good

Sulaiman

Thu Feb 16 2006, 09:05PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

For small high-power dissipation use a CPU heatsink/fan
(obviously not great for TO3 packages like the one you're using,
but good for most others, even isotop)

HV Enthusiast

Thu Feb 16 2006, 10:02PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Firkragg wrote ...

Well, il give it some tests, maybe, and tansistor will be heatsinked if needed.
But you must consider space taken by water cooled heatsink, I intended this to be compact (if possible).

Here water contacts silicon from all directions, maybe mistake is no turblence but doesnt matter a lot now.

The point is to make system smallest possible, and try not to use heatsink...

ell some crazyness is always good

Either way you are going to have to remove the heat. Even with liquid cooling you will need some sort of exchanger or chiller to remove the heat and i suspect this will take as much room as a heatsink and fan.

Also, it would be much more intelligent on your part to design your system to dissipate less heat. This would include selecting a much more efficient device. TO-3 packages are uncommon these days and the ones that are pretty outdated an relatively inefficient compared to today's newer devices.

What will your end application be with these devices?

Hazmatt_(The Underdog)

Fri Feb 17 2006, 06:03AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Hold on a minute here. Okay, obviously you guys think that Distilled water is the key, well, heh, let me tell you a little about distilled water!

There is an experiment which is a very dangerous one, which uses distilled water, highly distilled and essentially pure water. It is microwaved and the temprature of the water is actually above boiling, but since it lacks impurities and ions, it does not apper to boil. A fork is then touched to the water and it EXPLODES! hint hint!

Same happens in Anodize facilities, Highly purified rinse water DI tanks in stainless steel, which are also sometimes heated to boiling for sealing tanks, literally EAT the welded seams!!

So what is my point. You have DI water which wants ions desperately!!! Pass that water into a hot steel can! No more DI water, starts to conduct because of free ions in solution, eventually you have no isolation.

What I would do! Get a heatsink and put a thermal exchange system in that. It defeats the purpose, but it would be more reliable.

Dr. Shark

Fri Feb 17 2006, 09:04AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Hzmatt, I am sorry but I think the argument about "DI water which wants ions desperately" is BS. Still I dont like the idea for a number of reasons
1) Why use TO3 devices when you want efficiency?
2) Why use watercooling when you want to save space? Chillers, pumps etc. will be gigantic compared to the electronics.
3) When you want to circulate the water and still keep it deionized, you will need a device ($$$) in the cycle that continously removes ions.
4) Im pretty sure even DI water will eventually corrode the silicon. It does with GaAs in SS lasers.

Bjørn

Fri Feb 17 2006, 09:40AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

TO3 devices are found for free, that is good enough reason for using them.

Water carries a lot of energy so only a small amount per second is needed, therefore a well thought out design will be able to do away with the pump and rely on convection.

Since water has a very large specific heat capacity there may be no need for a heat exchanger at all if the average power is within a certain range.

That the chip slowly dies may not be a problem at all, they all do, It is just a matter of if it will last as long as you need in a certain application. Not all TO3 devices has the silicon exposed.

I would say it is an interesting idea that is not very practical since in most cases the problem can be solved in a simpler way.

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