I want copper copper copper! (well... maybe not)

I believe the contact junction between metals pose the biggest problem in removing the heat away from the diode. It is no good if you have a golden heatsink without a proper contact to the host. The heat will build up inside the host.
That is why I am always suspious about O-rings to tightend the sink inside the host. It does provide mechanical contact but the thermal contact isn't so good.

Since Gold..Copper and Aluminum are soft metals I would
beleive that they would be better at molding to a press
fit mechanical part under pressure. At least more so than
Steel or Iron....

Jerry

Yes you are correct in your thoughts about the junction and that is why they gold plate the copper in expensive laser systems, the gold is softer and acts like thermal paste between the gold plated LD die and the copper of the heat sink.

And again you are right "O" rings are no way to take up the space inside of the host when a sloppy heat sink is made, really a correct heat sink for the host should be made.

If the heat sink is made correctly to begin with it will be within .001 to.0005" tolerance and fit in the host like your hand in a glove !

When you screw the bezel ring down it should grab the heat sink so it is held tight with a full metal to metal contact, there should be no insulating rubber inside the host in contact with the heat sink if the heat sink is made correctly !

This is the difference between mass produced $9.00 heat sinks like some make and custom heat sinks like I make

good you can get right now, The best takes a little longer and costs a little more

Blord said:

I believe the contact junction between metals pose the biggest problem in removing the heat away from the diode. It is no good if you have a golden heatsink without a proper contact to the host. The heat will build up inside the host.
That is why I am always suspious about O-rings to tightend the sink inside the host. It does provide mechanical contact but the thermal contact isn't so good.

Click to expand...

I have a great deal of respect for RHD, but in this instance I feel like that copper is our best sink. I think a huge factor is that we AREN'T really doing much heat dissipation beyond the sink itself, so the more mass we can pack in the space with a good thermal conductivity is ideal.

Aluminum doesn't have the mass OR the thermal conductivity of copper.

I think a big hunk of copper that you can dump your diode's heat into is the way to go... but I will say that a whole nother can of worms to open up is the actual composition of the metals.

There are a lot of alloys of Cu and Al and that can hugely affect the Thermal Conductivity.

This is a neat discussion though.

Wolfman, I like your idea of skipping the module altogether and just building sinks that we can press the TO-18 or TO-56 diodes directly into with some thermal paste (carefully so you don't get any on the glass) is a great idea.

Someone is going to come up with a good copper sink that will go in a variety of hosts and kill the current modules.

Flaminpyro said:

Anodizing impedes heat flow.

Click to expand...

I read something suggesting that in some circumstances, anodizing can help. I'll try to find it, I think it had to do with helping transfer from the heat source to the sink. Let me look.

Here's my Choices since we are talking the best.

Diamond
Gold
Silver
Copper
Brass
Aluminum
maybe SS

Click to expand...

A couple of thoughts, off the top of my head. Graphite is interesting. Might make a good sink if there was a way to make it usable. I haven't looked into this at all yet.

Also, what about a hollow copper sink with a liquid that can hold a LOT of heat?

Just thinking aloud and daydreaming here.

rhd said:

I've highlighted, in blue, the clear winners. Not copper, not aluminum. Steel, iron, and nickel. Long story short, we're doing this backwards. We should be using copper for all of our Aixiz modules, and we should be using steel, iron, or nickel for our heatsinks. The exception, being in builds where you have a host made of material that conducts really well (basically aluminum or copper) and has some sort of substantial fin structure to increase the surface area with the air. Short of that, we should be waging war on "heat absorption" rather than "heat transfer".

Spending money on Aixiz's copper 3.8mm, 5.6mm and 9mm diode modules (made by forum vet PontiacG5) to carry the heat TO your heatsink makes a whole lot more sense than trying to make the heatsink itself out of an expensive metal that can hold less heat than steel

Click to expand...

I so agree with you. I put together computers and I ALWAYS see heatpipes to be copper while heatsinks themselves aluminum. And it makes sense. Copper transfers the heat really well, while aluminum dissipates the heat!

Problem with copper and aluminum combinations is then you run into galvanic corrosion...

Over time the copper and aluminum corrode eachother causing them to lose contact with eachother. That's what resulted in a lot of housefires back then, due to electricians combining aluminum and copper wires in houses. They would corrode so badly that the resistance would become so significant, that the actual wire caught on fire due to the heat.

You guys may need to keep this in mind too for case negative builds too! More resistance isn't a good thing... that and it would greatly inhibit heat transfer too.



And yeah, I kind of laughed at the steel comment... It's steel, we don't make heatsinks out of steel for a good reason. Most heatsinks in computers are aluminum with copper pipes. Copper holds it the best, aluminum MOVES it the best. Hence the elaborate system of copper pipes and aluminum fins. (regarding galvanic corrosion here, I'm not sure if it's a problem or not)

Le Quack said:

Problem with copp......


........And yeah, I kind of laughed at the steel comment... It's steel, we don't make heatsinks out of steel for a good reason. Most heatsinks in computers are aluminum with copper pipes. Copper moves it the best, aluminum holds it the best. Hence the elaborate system of copper pipes and aluminum fins. (regarding galvanic corrosion here, I'm not sure if it's a problem or not)

Click to expand...

And here i thought it is the other way arround!! The Cu absorbs the heat very fast and aluminium dissipates it , Hence the elaborate system of copper pipes and aluminium fins!!!

sinner said:

And here i thought it is the other way arround!! The Cu absorbs the heat very fast and aluminium dissipates it , Hence the elaborate system of copper pipes and aluminium fins!!!

Click to expand...

Yes! That's what computers has taught us And if that have to dissipate 80C of CPU heat, it should work with the same physics as heatsinking our diode.

Ah, I apologize. I had it backwards. P:

My fault!

Also, T_J, you are hilarious. :crackup:

Never really thought about it that way. Makes a lot of sense now that I think about it.
Thanks for enlighting us!

Here is a very intersting paper... It addresses something that has worried me a lot when looking at this topic. We like to run around with numbers like 200wmk for Aluminum and 400wmk for Copper - but those are for very pure alloys.

Even just a little bit of silicon or tin or other elements can DRASTICALLY reduces the thermal conductivity of both of these metals.

It turns out that Zinc is actually a dependable metal and even in alloy form it stays around 125wmk.

Kind of interesting!

http://www.cs.unc.edu/~pxfl/papers/heatsink.pdf

Well, typical 6061 aircraft grade aluminum that I use for my heatsinks (it's the best aluminum for machining, I am sure that's what most of us machinists use) has a better thermal conductivity of, at worst, like 150 W/(m-K), so it's still better than zinc. Copper, on the other hand, is pretty easy to get "pure," i.e. in most cases, when you buy copper stock, it should be pretty close to pure copper and not be alloyed.

Flaminpyro said:

Anodizing impedes heat flow.

Click to expand...

Sorry but I disagree with your statement.

Heat transfer by radiation of an object with a anodized dark flat surface
(I am not speaking of paint), will absorb and emit infra-red radiation at a
faster rate than an object with a light (brillant - shiny) surface.

One exampple:

Polished aluminium 0.05 Emissivity
Black anodised aluminium 0.70 - 0.90 Emissivity


Another exampple "High-Tech"

The "black" ceramic coating on the (HRSI and FRCI) high temperature tiles
from the Space Shuttle is necessary to help them to radiate heat during reentry.

And other more known examples, the radiator in a car, or the condenser on
the back of a refrigerator is matte black, and it's no an accident.

Well yeah, except radiation is very small in this case.

piferal said:

Sorry but I disagree with your statement.

Heat transfer by radiation of an object with a anodized dark flat surface
(I am not speaking of paint), will absorb and emit infra-red radiation at a
faster rate than an object with a light (brillant - shiny) surface.

One exampple:

Polished aluminium 0.05 Emissivity
Black anodised aluminium 0.70 - 0.90 Emissivity


Another exampple "High-Tech"

The "black" ceramic coating on the (HRSI and FRCI) high temperature tiles
from the Space Shuttle is necessary to help them to radiate heat during reentry.

And other more known examples, the radiator in a car, or the condenser on
the back of a refrigerator is matte black, and it's no an accident.

Click to expand...

Anodizing an aluminium heatsink will in fact reduce the heat transfer capacity of a very thin layer, ever so slightly 'insulating' the outer wall. At the same time, a darker anodized surface will indeed absorb AND pass off more infrared heat.

From what I've read... in the cases of dealing with forced air, bare aluminium was better; and in cases with restricted or no airflow, it was better to paint/ano a heatsink black.

In a case like this, where the heatsink will be encased in a tightly fitting host, IMHO having a bare aluminium heatsink to allow for better transfer to the host walls would make alot of sense VS having a black heatsink that won't absorb any infrared light since only a small % of it's body will ever be hit by IR and other lightwaves anyways... or is there something wrong with my reasoning here ?

As for car rads... I've had a bunch of euro cars that all had bare aluminium radiators. And intercoolers, why are they always silver ? AFAIK radiators are painted black so you won't see them in your car's grill cuz they're ugly, AND for corrosion protection, more than for heat transfer, if anything.

I think you are both right. FP makes great heatsinks, but they almost always are intended to add the mass of the body to the thermal mass, and not to radiate directly. Whereas, normally when I think of a heatsink, I think of a device meant to pull heat from a source, and generally dissipate it into the air.

If you ask me, I think a bigger issue is doing away with aixiz modules. Theoretically, you only have a small line of contact between the aixiz module and the host. Try to make two perfect circles of differing diameters touch in more than one point, it is not possible. You will see that the area between the two circles is exponentially proportional to the difference in their diameters. This is not feasible, though, because aixiz aren't perfectly round, and not all of us have tools that can produce enough pressure to press something like that.