# easy explanation asked for aluminium/Copper/silver, pls



## yellow (Apr 4, 2013)

lets look at the typical (led) light setup:
Aluminium housing + _some material _as mounting plate for the led (in direct contact to housing to pass on heat) 

now, looking at the heat capacity data on wiki, 
silver is *0.2* J/Kg
copper *0.4* J/Kg
aluminium *0.9* J/Kg
"but" the text says that this is the _amount of energy _needed to raise the temp of the material for 1 degree.

I somehow think to remember that the common view is: copper is better than aluminium,
but dont these numbers mean, that aluminium needs double the Energy to heat up the same?

What is my error and what material is best at the thermal part position?
(weight/cost not yet of interest)
:thinking:


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## AnAppleSnail (Apr 4, 2013)

1. How big is a kg of aluminum, vs a kg of copper? In other words, a copper flashlight and its aluminum-sized twin will weigh about 3x as much. Unless your flashlight is infinite in size (Or only used at peak power for short duration), it's more important to remove heat than to store it.
2. Thermal conductivity is important for continuous operation. But the limiting factor in most flashlight designs is not thermal conductivity, but the rate at which the flashlight can export heat to the environment at a reasonable temperature. This parameter is a combination of surface area, emissivity, and especially environmental temperature and air circulation, and other conductive factors.

I find that my well-designed flashlights below 10W never get especially hot in my hand. But any of my lights can get quite warm at 3W sitting on a table. There is no magic material that will make good thermal design. You have to plan well.

Reduce thermal resistance at each bottleneck (Thermal paste, very flat polished surfaces, etc). Increase heat rejection to the environment (Bigger, fins, held in hand). Those two things are far more important than aluminum vs. copper. Thermal interfaces range from something like 1 deg C/W for good junctions, to 10x or more that for the removal of heat from the flashlight.


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## StarHalo (Apr 4, 2013)

The number you're looking for is thermal conductivity:


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## gadget_lover (Apr 4, 2013)

AnAppleSnail nailed it. Try to imagine heat to be like water, and the LED as a mountain spring filling a pond. You can keep the pond from flooding if you soak up the water with a sponge, and that's like having a massive heat sink. Eventually the sponge is as wet as it can be, and can hold no more. The heat sink does the same thing and eventually reaches the same temperature as the LED. If the sponge has a place for the water to drain to, the pond will not flood. If something cools down the heat sink, it will continue to cool the LED.

The heat sink assembly is a conduit to move the heat away from the LED to a cooler area. Without a heat sink, a 3 watt LED running at full power will be damaged in seconds. A heat sink in an insulated light (plastic, for instance) will pull the heat away from the LED for several seconds or even minutes before it reaches a temperature where the LED will be damaged. 

Daniel


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## Colonel Sanders (Apr 4, 2013)

Here's an anecdotal example of an actual operating difference between aluminum and copper. I have two Mac's Tri-EDC hosts. One is aluminum and the other copper. Same size, same shape, and otherwise identical. On the highest mode (2.8a draw) the copper host takes MUCH longer to feel hot to the hand as compared to the aluminum host. Now it _will_ get hot, mind you, but it takes far longer. I'd say 3 times as long would be about right. I attribute this to the copper host having a far greater capacity to store heat before exporting it to my hand.

So, if I want to run the light on high for 5-7 minutes straight, I can comfortably do this with the copper host but not with the aluminum host. This is a huge plus in my book. 

The drawback to the copper, in my view, is that it certainly sits heavier in the pocket (but feels much sturdier and solid in the hand.)


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## gadget_lover (Apr 4, 2013)

There is often confusion about the benefit of a body that is slow to heat up. Some think that the slower transfer of heat means that the heat sink is more efficient. Others contend that the faster the heat gets to the surface of the flashlight, the more effective it is.

The truth is that the name of the game is to keep the LED below the temperature where it breaks down. If the surface of the flashlight is slow to heat then it's because the transfer of heat is slow. It is reasonable to also expect that it's slow to transfer the heat away from the LED. 

The slower heat is removed from the LED, the more the temperature rises in the LED. 

It is my opinion that the slower the flashlight body heats, the poorer the heat management.


Daniel


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## Colonel Sanders (Apr 5, 2013)

I agree with what Daniel just said 100%. However, we also must understand that when a host has more mass, it can remove more heat from the LED before transferring it to the atmosphere at a great rate. There is more heat storage capacity. The copper is pulling the heat from the LED just fine (so does aluminum obviously) but it takes longer for the copper host to "fill up" with heat and start to spill to the outside world.


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## SemiMan (Apr 5, 2013)

Colonel Sanders said:


> Here's an anecdotal example of an actual operating difference between aluminum and copper. I have two Mac's Tri-EDC hosts. One is aluminum and the other copper. Same size, same shape, and otherwise identical. On the highest mode (2.8a draw) the copper host takes MUCH longer to feel hot to the hand as compared to the aluminum host. Now it _will_ get hot, mind you, but it takes far longer. I'd say 3 times as long would be about right. I attribute this to the copper host having a far greater capacity to store heat before exporting it to my hand.
> 
> So, if I want to run the light on high for 5-7 minutes straight, I can comfortably do this with the copper host but not with the aluminum host. This is a huge plus in my book.
> 
> The drawback to the copper, in my view, is that it certainly sits heavier in the pocket (but feels much sturdier and solid in the hand.)




The copper one has 3.3 times the density, but also has only 44% of the heat capacity by mass. The end result is that the copper version has 50% greater thermal mass for exactly the same physical dimensions hence based purely on thermal mass, it will take 50% longer to get to the same temperature.

That said, the better conductivity of the copper will tend to improve its heat sink capabilities and hence over time more energy goes into the air and surrounding and if you are holding it in your hand, the copper version will be much better at transferring heat into your hand without getting warm.

Semiman


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## SemiMan (Apr 5, 2013)

gadget_lover said:


> There is often confusion about the benefit of a body that is slow to heat up. Some think that the slower transfer of heat means that the heat sink is more efficient. Others contend that the faster the heat gets to the surface of the flashlight, the more effective it is.
> 
> The truth is that the name of the game is to keep the LED below the temperature where it breaks down. If the surface of the flashlight is slow to heat then it's because the transfer of heat is slow. It is reasonable to also expect that it's slow to transfer the heat away from the LED.
> 
> ...




In many cases, especially a well designed flashlight, your opinion would be completely wrong.


I will put it into electrical terms as most people understand it better:

- Thermal resistance = electrical resistance
- Thermal capacity (or mass) = electrical capacitance
- Temperature differential = voltage differential
- Temperature = absolute voltage

Any element in a thermal system has both thermal resistance and thermal capacitance.

Let's say you try to dump 2 watts of energy into a small capacitor through a defined resistance. The capacitor will quickly rise in voltage. As the resistance is define, the voltage whatever it may be, will also go up quickly. Now if you have a big capacitor, the voltage on the cap will go up slowly as will the voltage on the other side of the resistor (I fixed power).

Now let's say I attached a 2W dissipating LED directly to a big copper block (or aluminum) ... just a big block. The high thermal mass of the block means that the block will be very slow to rise in temperature. At the same time, the high heat transfer capabilities of the material will work to keep the temperature of the block somewhat homogenous though obviously there will be a differential. After some period of time, the block of metal will hit equilibrium with the heat going into it and the heat being transferred out of it. With the exception of a small differential through the block (it has a high conductivity), the LED temp never gets much higher than the surface temperature.

So let's take a copper (or aluminum) block that is 1/8 the volume (and 1/4 the surface area). The block will heat up much faster until it reaches equilibrium. However, because it has 1/4 the surface area, that equilibrium temperature at the surface w.r.t. room temperature is now 4 times higher. The thermal resistance between the surface of this smaller block and the LED may be 1/2, but since the conductivity of the materials is so high, it make little difference in terms of a thermal differential. Hence in this scenario, the increase in LED temperature will be 4x.

The only thing you can surmise from a hot bodied flashlight is that what is inside is even hotter.

A flashlight body with no fins will heat up much faster (and get much hotter overall), then one with a ton of fins with the end result being a hotter LED during all the operation.

If you "could" make a graphite bodied flashlight (graphite conducts fantastic in the alignment of the strands), then the outside would be hot quicker and the LED would potentially be cooler in equilibrium. However, with very little thermal mass, if you had brief "turbo" modes, during the turbo mode, the LED would be much hotter than an aluminum or copper body that could absorb (like a capacitor) the thermal energy spike.

Thermally enhanced plastics would get hot quicker than aluminum or copper as well, however, due to their low thermal mass and higher thermal resistance, the LED will absolutely be hotter both in transient and equilibrium conditions.


Where a slowly heating body would be a concern would be with materials with a high ratio of thermal mass to thermal resistance. The obvious one is non thermally enhanced plastic bodies. All that happens there is the LED gets really hot, then the interior gets really hot, which make the differential across the plastic body enough to transfer the heat being generated.

The other case is less obvious, titanium flashlights. Titanium on a volume basis has a similar thermal mass to aluminum. On the other hand it is a poor thermal conductor, about 1/7 that of aluminum. Because of that there will be a greater thermal gradient across the material for equivalent energy transfer. On the other hand the thermal mass is high so it will take time before the exterior heats up. It is not an indication of poor thermal management per se, just poor material choice.

Semiman


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## AnAppleSnail (Apr 5, 2013)

And still in most flashlight applications, the bottleneck is in keeping the outer surface of the flashlight cool enough that it can accept heat from the interior of the light and maintain an at-LED steady-state temperature that is acceptable. In other words, no matter how big the thermal path is, the traffic jam comes at the edge of the flashlight.


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## SemiMan (Apr 5, 2013)

I think that is true in a lot of cases, but depending on the design tradeoffs, it may not be worse than the other thermal resistances combined. You don't have thermal bottlenecks per se., all resistances add in series. If you have some air movement through usage that can make a big difference too.

Semiman


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## gadget_lover (Apr 5, 2013)

SemiMan said:


> In many cases, especially a well designed flashlight, your opinion would be completely wrong.



You are quite entitled to your opinion, but I find that it does not match my experiences or measurements. No matter what your material, the heat is being generated continuously inside the light and has to leave it somehow. A large mass without an effective way to shed heat only delays the point in time where the LED overheats. 

One of my assumptions for a well designed flash light is that it can be used continuously until the battery dies. That may be 1, 2 or 3 hours. If I continuously generate heat from a 3 watt LED for an hour and the flashlight never warms up, then the light either has a lot of surface area or it's baking hot inside. 

The best way to measure the effectiveness of the cooling is to measure the output of the LED as soon as it is lit and then after running continuously for a little while. If it dims appreciably the cooling is suspect. 

BTW, I like this bit...


> It is not an indication of poor thermal management per se, just poor material choice.



Material choice IS part of thermal management. Poor choices mean poor performance.

Daniel


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## yellow (Apr 6, 2013)

... I am still not getting the explanations ...

make it more detailed and easy, for just a theoretical "discussion" 

1* 18650 led flashlight ... led mounted on thermal plate ... thermal plate pressed into aluminium "barrel" body ...
so the size of the plate is roughly _one coin_
(so weight and/or cost is not a factor)

be it from:
titanium --> extremely bad for the led
aluminium --> gets heat away better
copper/brass --> gets heat away best (and at the same time heats up less than the alum?)

or does simply not make sense to decide between alum <-> copper in that setup?
:thinking:


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## AnAppleSnail (Apr 6, 2013)

Titanium isn't so bad. Most of the modders find that below about 5W in aP60 host, most metals work well if your junctions are good. Bad junctions can lead to much more thermal resistance (degrees hot per watt) than metal choice does. Degrees hot per watt is tough to calculate, but it's more important than thermal conductivity of the bulk material. The details aren't so simple, and you'll have to think.

In useable design, you'll have a ” self sufficient” power level where the light stays cool unaided, and a higher mode where it needs help (fans, water, a hand). These levels represent different assumptions about design, which is part of why you're getting conflicting answers. My experience with P60 hosts is that very good thermal contact is more important than exotic materials. It's also cheaper than trying to learn to braze-coat copper on to allow goofy thermal connections. The next most important thing is thermal mass in the host, in my experience.

So how does one craft good thermal junctions of low thermal resistance? A coin of amy metal probably has 1 or less C/W resistance. No matter the metal (within reason). Machine-flat, smooth mating surfaces. Interference fit and thermal grease. Large, smooth areas of excellent thermal contact. This is why shimming or wrapping P60 hosts is key. 

I suggest a thermal-reservoir (heat sink, literally) just behind the LED. This warms ups with the LED, smoothing out temperature spikes, and passes heat to the light. Copper and aluminum are cost effective. Has anyone tried silver? Gold? Those gains might be marginal. This slug is in excellent contact with the body, and serves as a low-resistance path. Surfaces are key. Possibly more so than material, at reasonable power levels. At high power levels, you have to get it ALL right.


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## SemiMan (Apr 6, 2013)

gadget_lover said:


> You are quite entitled to your opinion, but I find that it does not match my experiences or measurements. No matter what your material, the heat is being generated continuously inside the light and has to leave it somehow. A large mass without an effective way to shed heat only delays the point in time where the LED overheats.
> 
> One of my assumptions for a well designed flash light is that it can be used continuously until the battery dies. That may be 1, 2 or 3 hours. If I continuously generate heat from a 3 watt LED for an hour and the flashlight never warms up, then the light either has a lot of surface area or it's baking hot inside.




It is not an opinion, it is physics.

A well designed flashlight (thermally) with a high thermal mass will heat up slowly. If it heated up faster, that would just mean it had less thermal mass. If it had less thermal mass, then it would probably also have more thermal resistance. A flashlight exterior that gets quickly hot could just as easily be a bad design as a good design.

Semiman


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## Russel (Apr 13, 2013)

gadget_lover said:


> There is often confusion about the benefit of a body that is slow to heat up. Some think that the slower transfer of heat means that the heat sink is more efficient. Others contend that the faster the heat gets to the surface of the flashlight, the more effective it is.
> 
> The truth is that the name of the game is to keep the LED below the temperature where it breaks down. If the surface of the flashlight is slow to heat then it's because the transfer of heat is slow. It is reasonable to also expect that it's slow to transfer the heat away from the LED.
> 
> ...



The body of a flashlight can be slow to heat up and but also transfer heat faster than another flashlight up to a point depending upon the construction.

Consider two flashlights, same LED, same body, same heat sink. One heat sink made of copper, one of aluminum. The LED would be cooler with the copper heat sink due to the higher thermal conductivity. But, because the copper takes about [50 percent more] heat to raise a given volume of it one degree compared to aluminum, the body of the flashlight would remain cooler until the heat sink reaches thermal saturation. 

So, the copper heat sink would keep the LED cooler and it would take longer for the body to heat up, that is until the flashlight reached thermal saturation. At that point the heat dissipation of the flashlight body becomes the bottleneck.

If the flashlight is used intermittently for short periods of time, the body of a flashlight with a copper heat sink would be cooler than the same flashlight with an aluminum heat sink of the same dimensions. (Assuming that the copper heat sink hasn't reached thermal saturation.) Of course, the flashlight with the copper heat sink would take longer to reach ambient temperature, when turned off, than the flashlight with the aluminum heat sink because of the lower thermal difference between the body and ambient.


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## Russel (Apr 13, 2013)

yellow said:


> lets look at the typical (led) light setup:
> Aluminium housing + _some material _as mounting plate for the led (in direct contact to housing to pass on heat)
> 
> now, looking at the heat capacity data on wiki,
> ...



How much does a cubic centimeter of each metal weight?

Ag
1.00kg = 95.3 cm^3 
1000/95.3 = 10.49g/cm^3

Cu
1.00kg = 112 cm^3 
1000/112 = 8.93 g/cm^3

Aluminum
1.00kg = 370 cm^3 
1000/370 = 2.7 g/cm^3

Taking the heat capacity of each metal from the above quote, what is the heat capacity of a cubic centimeter of each metal?

Sliver .2 * .01049 Kg = .0021
Copper .4 * .00893 Kg = .0036
Aluminum .9 * .0027 Kg = .0024

Although copper isn't as high as I thought, it does have a higher heat capacity per given volume than that aluminum or silver. Of course, silver has the best thermal conductivity, with copper next and aluminum last.

Thermal conductivity:

Silver 429
Copper 401
Aluminum 205


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## AnAppleSnail (Apr 13, 2013)

The next step is to compare the thermal resistance of 1mm of these metals to the necessary junctions in the light. The one internal to the LED, the thermal bridge from LED to heatsink, heatsink to host, and host to air. Characterizing these for a given host allows a good comparison of where your priorities are for improvements.


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## Russel (Apr 13, 2013)

I think the ideal configuration, provided that good mechanical thermal joints can be obtained, is the LED on a coin sized piece of silver, maybe the size of a nickel, to maximize thermal transfer from a small surface area, the LED, to a larger sized area, the sliver "coin". The silver "coin" then mounted on a copper heat sink that is in good thermal contact with the flashlight body.

That would leave four main thermal connections (excluding the internal LED junction to the LED case). The thermal connection between the LED case and the silver coin, between the coin and the copper heat sink, the joint between the heat sink and the flashlight body, and finally, between the body and ambient air. When working with the older AMD processors that have a relatively small surface areas (about the size of you pinky finger nail) I found that adding a slab of silver between the CPU and heat sink would help conduct the relatively high heat of the CPU from a small area to a larger area of a copper heat sink better than having the CPU directly in contact with the copper heat sink, despite adding another thermal joint. I would expect, given all the mechanical surfaces are well finished and flat with good mechanical connection, that this would be true with a high powered LED.

Of course, an elephant still remains in the room. Once the flashlight parts reach thermal saturation, the entire heat dissipation of the flashlight is limited by the ability of the flashlight body to dissipate heat into the ambient air. If you are talking about a 1 to 3 watt flashlight, this shouldn't be a problem. If you are talking about a 20 watt flashlight, this is a problem unless you are only using the light intermittently, or it is a dive light that is used under water.


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## Russel (Apr 14, 2013)

yellow said:


> ... I am still not getting the explanations ...
> 
> make it more detailed and easy, for just a theoretical "discussion"
> 
> ...



I would recommend a copper thermal plate. I will take more heat (by about 50%) than aluminum to raise it's temperature by the same amount (it has greater thermal inertia), and it conducts heat much better. A copper thermal plate will weigh more than an aluminum one of the same size and shape, but with a smaller flashlight that shouldn't be something to be concerned about. I would recommend aluminum next and brass last. Although brass contains copper, it doesn't conduct heat as well as aluminum.

It isn't that copper heats up less than aluminum. It take more heat to raise the temperature of a given _volume _of copper. One way of thinking about it is that one cubic inch of copper weighs a lot more than one cubic inch of aluminum. It weighs more because it has more mass. It basically has more material occupying the same space. Because there is a lot more mass, it takes more heat to raise the temperature of a cubic inch of copper than it does aluminum. Now, if instead you were talking about a given weight, such as a Kg of copper and a Kg of aluminum (meaning the same mass), the aluminum would take more heat to raise it's temperature because it has a higher heat capacity, but a Kg of aluminum would occupy much more volume. So, if volume (size) isn't a big issue, aluminum might be a better choice. It has good thermal conductivity and good heat capacity. But, if you are limited by volume (size) such as in a small flashlight, then the higher density of copper gives you more thermal inertia and better thermal conductivity.


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## Leo Kluger (Aug 12, 2013)

Thanks for the interesting discussion. Is it feasible to modify a stock Fenix PD-35 to remount the LED on a nickel-sized copper or silver heatsink? 

Or while removing the LEDs from their current substrate, is it all too easy to shatter something critical.


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## fyrstormer (Aug 13, 2013)

yellow said:


> looking at the heat capacity data on wiki,
> silver is *0.2* J/Kg
> copper *0.4* J/Kg
> aluminium *0.9* J/Kg
> ...


The important metric in flashlights is *volume, not mass*, because the designer is aiming to achieve a certain size with their design. (generally mass is only a secondary concern, if they care at all.) Two heatsinks of the same volume, one made of copper and the other made of aluminum, will have very different masses. The aluminum heatsink will be much, much lighter, so the number of joules required to heat its lower mass to the same temperature will also be much, much lower. You can't dissipate heat without getting the heatsink to a higher temperature than the surrounding material, so the ability to quickly heat aluminum to a high temperature allows it to dissipate heat very effectively.

That being said, a heavier copper heatsink will have more heat-storage capacity than the aluminum heatsink, because its mass is so much greater. That can be beneficial in situations where the emitter is expected to run very hot for a short time, or where there's no practical way to dissipate heat into the air fast enough while the light is on, such as in a very large light where heatsink has a low ratio of surface area per unit of volume.

EDIT: Someone mentioned titanium as well. Titanium would be a poor heatsink, but it's a fine shell material, because the shell is thin. The thinness of the shell means that durability is a greater concern than heat dissipation. However, the thinness of the shell *also* means it has a high ratio of surface area per unit of volume, so as long as it has a good thermal connection to the heatsink, a titanium shell will still heat up quickly and dissipate heat into the surrounding air effectively. There are IR photos of titanium lights that appear to disagree, but they actually prove the point -- the IR camera wouldn't be able to see the temperature of the titanium shell if it weren't radiating heat effectively. Those same IR photos show the heat more closely concentrated in the head of the light, instead of conducting down the length of the battery tube, and some people say this means the titanium can't conduct heat into the user's hand -- but I personally think that's a *good* thing.


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## SemiMan (Aug 13, 2013)

fyrstormer said:


> TThe aluminum heatsink will be much, much lighter, so the number of joules required to heat its lower mass to the same temperature will also be much, much lower. You can't dissipate heat without getting the heatsink to a higher temperature than the surrounding material, so the ability to quickly heat aluminum to a high temperature allows it to dissipate heat very effectively.



This statement is inaccurate or at least exaggerated and is covered in post #8 above and again in #17. The amount of joules to heat the aluminum is not "much much" lower.

By volume, aluminum has approximately 71% of the thermal mass of copper. That is pretty close.

In addition, the comment that because aluminum heats up quicker allows it to dissipate heat fast is wrong. The ability of something to heat up "quickly" generally is indicative of a poor radiator of heat, not a good radiator. The fact it is getting hot means it is not dissipating, never a good thing. There is some complexities. A poor thermal conductor could be cool on the outside and warmer on the inside ... again not good. The aluminum is "hot" because it is a good conductor and hence the temperature differential between what is generating heat and the radiating surface is low. The same would be true of copper as well.

Semiman


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## chillinn (Jan 2, 2015)

This thread is amazing. I sat long and hard before giving into the compulsion to ask...

Why would anyone want to use such poor thermal conductors such as Ag, Cu or Al?

I'm not kidding. There is a cartel that is literally terrorizing technology, retarding it, slowing its progress --because of greed/power.

Carbon isn't very sexy, except when its nanosomething or a diamond. Assuming de Beers, et. al, & slave/blood miners, went down like chumps with the Axis, and the market became flooded with diamond and it became actually a material with a (pulling this out of the air) cost that was on par with extremely high-quality-difficult-to-manufacture-ceramics or whatever may be down Corning's roadmap or maybe fell off the Space Shuttle, wouldn't, then, diamond put all metal to shame, regarding keeping the LED cool? Couldn't the LED itself be a diamond (remember the terms... we've hypothetically toppled de Beers regime... so 1k diamonds go for about $50 a pair)? So how bright and powerful could (just guess) a diamond flashlight get, compared to mere plastic/metal? Could we make our imaginary light twice, thrice as bright and heat producing? Ten times brighter? 

Before jaw dropping the idea, because in reality diamonds are crazy expensive, please consider diamond should not be what it is, and it is what it is only through economic manipulation, not inherent value. It should instead be a mere commodity material (like synthetic ruby/sapphire) that tech designers, manufacturers should be able to use and develop. Ignoring a material with the best possible electric/thermal conductive characteristics can't be good for the progress of science or technology. 

Who wants one? Why would it be a terrible idea (again, ignoring the real market, replaced with adjusted "should only cost")? What would the cost need to be before it would be an interesting alternative even if only for heatsink or LED?

Apologies in advance if I have in anyway hurt the sanctity of this thread. This is one of the rosetta stone threads.

edit: I am half-expecting the "I had one of those. Felt light in the hand, kind of greasy, kept slipping out of grasp until one day, it cracked... a few more drops and it shattered. Had to convert it to jewelry. Have you tried one in stainless? Much better if you're a dropper."


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## SemiMan (Jan 2, 2015)

They just don't make tin hats like they used to.

Debeer's monopoly, pretty much dead, was almost exclusively for gem grade diamonds, not industrial diamonds which is what would be used in a flashlight.

Diamonds are already used for thermal conductors in semiconductors where the price is warranted.

Industrial diamonds are already <$10/Carat, but even at that price, it would still make for a ridiculously expensive flashlight, though you could make a diamond slug that then transfers into copper ... similar to what is already done for select power semiconductors for specialized applications.

A diamond flashlight .... care to share how you plan to machine this ridiculously expensive unit .... because keep in mind that best thermal conductor is still pretty useless if you can't get the heat out to the air.

By total volume today, most industrial diamonds are man made with CVD.


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## chillinn (Jan 2, 2015)

SemiMan said:


> They just don't make tin hats like they used to.
> 
> Debeer's monopoly, pretty much dead, was almost exclusively for gem grade diamonds, not industrial diamonds which is what would be used in a flashlight.
> 
> ...



"Gem quality" is synonymous with "big enough for a ring." Industrial diamonds are tiny and would then need to be aggregate, so its like a 3D puzzle, find the edges and just keep looking at the box cover. Preferably, however, I'd start with a good sized solid synthetic diamond block and then use a tiny piece of my skull to mill it. Seriously, and obviously, I'd do it with harder synthetic diamond. Some synthetic diamond is not as hard as natural, but the actual hardest known material is indeed yet even harder synthetic diamond.

Perhaps deBeers is actually not pulling strings, but I think nothing short of a diamond volcano will change the market value of large samples of the hardest thing polished really nice. But those things would be a lot more useful elsewhere, considering one can never get the value out of them one puts into them. My brother introduced the idea of an "engagement VCR" back in the day. I think he's on the right track.


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## TEEJ (Jan 2, 2015)

chillinn said:


> "Gem quality" is synonymous with "big enough for a ring." Industrial diamonds are tiny and would then need to be aggregate, so its like a 3D puzzle, find the edges and just keep looking at the box cover. Preferably, however, I'd start with a good sized solid synthetic diamond block and then use a tiny piece of my skull to mill it. Seriously, and obviously, I'd do it with harder synthetic diamond. Some synthetic diamond is not as hard as natural, but the actual hardest known material is indeed yet even harder synthetic diamond.
> 
> Perhaps deBeers is actually not pulling strings, but I think nothing short of a diamond volcano will change the market value of large samples of the hardest thing polished really nice. But those things would be a lot more useful elsewhere, considering one can never get the value out of them one puts into them. My brother introduced the idea of an "engagement VCR" back in the day. I think he's on the right track.



The flaws and carbon flecks, etc, are as much of what degrades a stone from "gem quality" as size...there can certainly be large heavily flawed stones that would be ok for industrial use and not as gems, etc.

Finding flashlight sized chunks of industrial grade diamonds to mill into the desired shapes would be a bit nutz...on any kind of commercial basis.

Taking diamond sand, etc, and "fitting it together" to form a larger stone (Aggregate), and making them attach to each other, would also be nutz, in practice. 

IE: Its not a commercially viable idea....even if you could physically do it.

I don't think it would be worth mining the diamonds, if the flashlights made from it were affordable....the math doesn't work.


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## chillinn (Jan 2, 2015)

fair enough! forgetting the host, then diamond for led itself, is the query. Aren't there already sapphire leds? Wouldn't a grown diamond led be superiour in every way to any LED that's ever existed?


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## precisionworks (Jan 2, 2015)

Except for cost


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## TEEJ (Jan 2, 2015)

Yeah, synthetic diamond can be used, but, not cost efficiently....so, once again, in a lab, sure...in things that are expensive enough to start with to justify the cost, sure...for flashlights? Not so much...its not commercially viable.

Sapphire is already in use in that application...its ~ 80% of the substrate market as is....they sell wafers of it for many applications.


Diamonds are harder to synthesize...and, more expensive.


There's no conspiracy to prevent uses here...its all easily understood economics of scale...that's all that's going on.


Even if you had a base of "cost is no object" customers lined up...the advantages would be incremental in nature, and nothing you'd be able to justify on a performance basis to cost basis ratio.

How much more would someone pay for a flashlight to have it be just as bright and a little smaller, or the same size and a little brighter, etc? 100x more? 2x as much? 

The demographic would be unlikely to support the business model...the economy of scale is not there.


If it was 100x brighter, OK, then you'd have something....but you're taking about a few percent improvement over cheaper alternatives, not orders of magnitude.


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## SemiMan (Jan 2, 2015)

chillinn said:


> "Gem quality" is synonymous with "big enough for a ring." Industrial diamonds are tiny and would then need to be aggregate, so its like a 3D puzzle, find the edges and just keep looking at the box cover. Preferably, however, I'd start with a good sized solid synthetic diamond block and then use a tiny piece of my skull to mill it. Seriously, and obviously, I'd do it with harder synthetic diamond. Some synthetic diamond is not as hard as natural, but the actual hardest known material is indeed yet even harder synthetic diamond.
> 
> Perhaps deBeers is actually not pulling strings, but I think nothing short of a diamond volcano will change the market value of large samples of the hardest thing polished really nice. But those things would be a lot more useful elsewhere, considering one can never get the value out of them one puts into them. My brother introduced the idea of an "engagement VCR" back in the day. I think he's on the right track.



Gem Quality is synonymous with color and clarity. Most industrial diamonds are not remotely clear. Gem quality stones are sold into the industrial diamond realm, but these are only the ones too small to cut and represent a very small portion of the overall industrial diamond business.


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## chillinn (Jan 2, 2015)

SemiMan said:


> Gem Quality is synonymous with color and clarity. Most industrial diamonds are not remotely clear. Gem quality stones are sold into the industrial diamond realm, but these are only the ones too small to cut and represent a very small portion of the overall industrial diamond business.



These characteristics are arbitrary. I know were way off topic, but "gem quality," even though gemmers (super-special geologists!) have taken their close observations to a science, is really amazingly subjective when it comes down to how pretty it is... though there are clear, colorful, flawless, perfect stones, the flaws only matter most to the jeweler and the cost to the (say) suitor, not the wearer. Champaign is a color that is relatively new in gemstones. I'm pretty sure before someone figured out how to market it, it was an industrial quality variety. I think they're ridiculously ugly. Take the nastiest industrial diamond, polish it up, and it will go nicely in a setting... SOMEONE will buy it, even if it is opaque. Polished coal doesn't look that different from onyx.

The fashion diamond peddlers didn't just mess with the market, they messed with our perceptions. About a hundred some years ago, the diamond engagement ring didn't exist.


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## SemiMan (Jan 3, 2015)

Tin hatting again. Industrial diamonds are not remotely like gem diamonds. They are not clear ..... Not remotely close. They are not remotely perfect. No one would confuse them. Colored diamonds of gem quality are still "clear" in that they are homogenous ... Relatively free of imperfections.

I am not saying the gem martet was not manipulated but big difference from industrial diamonds.

Colored diamonds of gem quality have always been more expensive than colorless due to their rarity.

Posted by really crappy Tapatalk app that is questionable wrt respect of personal data.


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## chillinn (Jan 3, 2015)

http://www.allaboutgemstones.com/rough_diamond_jewelry.html

The market for colored diamonds of gem quality must have a direct effect on the cost of industrial diamond, and thus all possible applications. If gem-quality diamond wasn't pretty, do you think the industrial market would ignore them... ? Compare diamond to gold: one could never say what I said about diamonds about gold, i.e., the lust for gold itself, and for its decorative applications, and even its hoarding, has not had much effect on the advancement of tech, in fact this all served to make gold more available to tech-- and many a gold/silver smith advanced science further, expanding tech applications. Metal's a different thing, easier to put just a tiny bit anywhere, so where it was desired by engineers, they were free to use it. I'm not that kind of engineer, but I realize that engineers don't as a whole don't project personal significance on their materials, not any mystical nor social significance when they're designing or building something that has no such significance. Yet this bs sort of changes what's available, because of cost. I hope I'm not bashing humanities or arts too hard, that is important, but not if it adversly affects our advancement in science and technology. Can I get... any more off topic? Tempt me, and I may be able to exaggerate further... only to spotlight the point: all things being equal the engineer chooses the best materials with the best characteristics for their purpose... but all things aren't equal for a lot of reasons. One of them is really annoying.


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## Bucket (Jan 3, 2015)

I'm with Gadget Man.

To the OP...

As simple as I can make it, the two main issues in the famous Al vs Cu debate are:

1. Copper is roughly 3x denser than Al, while it has 45% the specific heat capacity (roughly). Doing the math... 3 * .45 = 1.35 volumetric heat capacity (It's actually higher than that). A given volume of copper will absorb 35% more heat than the same volume of Al if no heat is transferred out of the system.

2. Copper conducts heat at a rate roughly 2X that of Al. I think this part is pretty self explanatory. Copper moves heat away from the die better, thus keeping it cooler.

I guess I should mention a third thing since I've seen it talked about in the thread and it is relevant. Flashlight surface temperature is very important since *heat transfer through convection to the air is driven by the difference in temperature* between the two bodies at the interface (body temp - air temp). A hotter body will transfer heat much more quickly than a cool one. This is where many people get confused when they hold a light that transfers heat well. The body should be warm. That's how the heat gets out. Without the difference in temp between the air and the body, there just isn't much heat transfer. 

Anyway, copper is better in both regards. It absorbs more heat per given volume and it better transports it to outside of the light where it can be convected and radiated away.

Regards


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## chillinn (Jan 3, 2015)

Bucket said:


> I'm with Gadget Man.



I'm with the copper group, myself. However, I don't have the phsyics, math, geology, to wonder... and if someond doesn't mind that knows, I'd like to see the comparison... if you'd accomodate my wondering... let's assume that diamond was common as water, and that it was as workable as metal. How would diamond compare to copper (re: density/heat capacity?) Just for fun, if its not too much trouble (you can flub the math if you're mathy and a reasonably accurate educated guesser). I'm hoping for an answer like "its twice as good at heat as copper, so the light could be x brighter with no harm to LED-- but remember this is impossible" or something along those lines...


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## Bucket (Jan 3, 2015)

Chillinn, I got all of the following from engineeringtoolbox.com. Lots of good stuff there.


AluminumCopperDiamondThermal Conductivity2054011000Specific Heat Capacity897385516Volumetric Heat Capacity242133841677Density2.78.793.25




Units are all SI.

So from the chart, diamond kicks *** transferring heat compared to either copper or aluminum. It's 5X better than Al and 1.5X better than copper.

From a volumetric heat capacity perspective it's not so good though. Last Place. So if the thermal path to the outside of the light is poor (Ti), a diamond HS would not be a good choice.


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## chillinn (Jan 3, 2015)

Bucket said:


> Chillinn, I got all of the following from engineeringtoolbox.com. Lots of good stuff there.



Gracias, amigo! Now I can sort of think about stuff that can't be... just for fun 


And thanks for the analysis! I'll shut up about diamond now.


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## gadget_lover (Jan 5, 2015)

chillinn said:


> FWIW:
> 1. LED's create lots of heat
> 2. diamond has good thermal properties
> THEREFORE: Diamond should be used for LED
> ...



That is a valid argument only in very constrained circumstances. In the real world you will never find a need that will justify the expense and added technologic problems. The question that has not been asked is this; Is there some value added by using diamond over other substances, based on something that it will do that other techniques / materials won't do?

The transfer of heat from the die to the air is only one of the limiting factors for making bright lights. If you get 100% of the 12 watts of heat from a high power LED to pass through the body to the hand of the user, the user will quickly stop using it. To get rid of that heat you still need a way to move that heat away from the light before if burns the hand and cooks the batteries. 

If I want to make a light as bright as a 3 watt light that uses a diamond based heat sink and body to allow higher drive, all I have to do is put a second LED in the head of an existing $10 light. 

In other words, you are pursuing an idea that is not only expensive, it's impractical and does not fill an existing need. 

IMHO

Dan


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## Bullzeyebill (Jan 6, 2015)

OK, it started in post 39, and lasted through the last post. SemiMan, and chillinn getting into it with impolite comments back and forth, taking over 23 posts, discussing what had already been confirmed as off topic. The thread was hi-jacked and is probably not worth saving. I removed those 23 posts for the record as they are CPF Rule 4 violations. Any responses to my action must be done via PM. Thanks,

Bill


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## 4rmless (Apr 20, 2015)

Are Copper and Aluminium the only choices? Are there alloys with similar properties?

For instance, I understand the magnesium alloys used in laptop casings are selected based on a combination of machinability, weight, durability and thermal properties. Magnesium has a very very high specific heat capacity and fair thermal conductivity, a good mix, though it isn't too dense. I've no clue what happens to those properties in alloys, anyone else?


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## precisionworks (Apr 21, 2015)

IMHO the best single source for all things metal is Metals Handbook Desk Edition. I have the first edition (1984) & there's a newer second edition (1998). Both are available through inter library loan in the USA. Very thorough coverage of all metals & alloys, about 1500 pages.


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