# 1 MC-E vs multiple XR-E which needs more heatsink?



## lightime (Jul 2, 2009)

If you have a single MC-E vs an array of 2, 3 or 4 XR-E Q5 running at the same mA, lets say 1000mA... which needs more heatsink the single MC-E or the team of XR-E?

Would there be any difference at other mA levels at all or would one option need consistently more heatsink?

Thanks in advance for any guidance.


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## yellow (Jul 2, 2009)

I d think the quad needs more sinking, because the heat comes from just a single spot, while the four leds are spread over the mounting sheet.
... no matter what current.


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## PaulH (Jul 2, 2009)

I agree with Yellow.

I have a 4 x XR-E (R2) set-up, running at around 1000mA per LED (with one of Download's multi-sinks). This seems to run on high quite a bit cooler than 1 x MC-E at 2800mA (700mA per die) - with a brightlumens heatsink.

As for efficiency, then that is going to be a slightly different matter.


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## mds82 (Jul 2, 2009)

which ever one has more power going to it will require more heatsinking.

4 XR-E @ 1000ma = 4000ma total
1 MC-E @ 2800ma = 2800ma totla

the 4000ma will require more heatsinking.

if its the same ma total for both, the heatsinking will be virtually the same.


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## 2xTrinity (Jul 2, 2009)

mds82 said:


> which ever one has more power going to it will require more heatsinking.
> 
> 4 XR-E @ 1000ma = 4000ma total
> 1 MC-E @ 2800ma = 2800ma totla
> ...


lighttime specified the same current would be flowing through each. That is, 4 XR-E @ 700mA, or 1 MC-E @ 2800mA. Also, assuming similar Vf for each (that is, same total power consumption)

The MC-E will require better heatsinking all else equal because the power is concnetrated in one spot. This is the very reason why the MC-E is only rated for 2800mA total, NOT 4000mA (like 4 XR-Es)


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## lightime (Jul 2, 2009)

This is the way I was thinking.... assuming same current through each. I thought the mc-e would require less heatsink the higher you went up in current where you'd be pushing the xre-'s harder. But say at 350 mA and 500 mA for example where they are all still pretty much well within specs what would the heatsink requirements be then...who would need more heatsink a lone mc-e or a couple (2+) xre's? Oh, and the team of xre's would be sharing a heatsink.



2xTrinity said:


> lighttime specified the same current would be flowing through each. That is, 4 XR-E @ 700mA, or 1 MC-E @ 2800mA. Also, assuming similar Vf for each (that is, same total power consumption)
> 
> The MC-E will require better heatsinking all else equal because the power is concnetrated in one spot. This is the very reason why the MC-E is only rated for 2800mA total, NOT 4000mA (like 4 XR-Es)


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## phalanx (Jul 2, 2009)

lightime said:


> This is the way I was thinking.... assuming same current through each. I thought the mc-e would require less heatsink the higher you went up in current where you'd be pushing the xre-'s harder. But say at 350 mA and 500 mA for example where they are all still pretty much well within specs what would the heatsink requirements be then...who would need more heatsink a lone mc-e or a couple (2+) xre's? Oh, and the team of xre's would be sharing a heatsink.


 

Heat transfer is partially a function of the area of the physical interface between two materials. The larger your surface contact area, the more heat (in Watts) you can transfer. If total power between multiple XREs and a MCE are the same, you will be able to transfer heat at a higher rate from the multiple XREs due to the larger overall contact area. This means your XREs will be cooler than the MCE.


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## Marduke (Jul 2, 2009)

And total light output will be higher due to the lower junction temp.


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## ergotelis (Jul 2, 2009)

Both need the best possible heatsinking.But because of the fact that in a small area mce is puting out a lot of heat, it needs better heatsinking. Of course,4 cree need too, but the fact that the 4 seperate dies are not that close, it helps the heat to be spread out better. If you have to choose between MCE and 4 cree, i would go with 4 cree. You won't have to care at all about donut holes and output will be a bit more. 
Also,in a future update of your leds, i guess that a SST90 would not be as much efficient as 4 XP-G!


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## lightime (Jul 2, 2009)

Looks like everyone pretty much agrees. Makes sense to me after reading your posts and thinking about it a bit more. Actually sounds more like common sense now. 

I thought the MC-E handled a lot more power than the "poor little" 4 XRE's because In my mind I was thinking the MC-E handled 2,800 while the XRE handled "only" 1000 so the MC-E had more headroom....but I overlooked the fact like 2xTrinity mentioned that we are talking 4 x 1000 with the XRE!! So it's actually 2 strikes against the MC-E when up against a set of 4 XRE:

1) each corner handles max 700mA (2800max vs 4000max)
2) Not as much area to transfer heat with the single MC-E

Thanks for clearing all this up guys!! :twothumbs


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## Gryloc (Jul 3, 2009)

Hey there again! So, yes 4 XE-E emitters are better than 1 equally matched MC-E. I just wanted to poke in to tie this to your other thread, lightime. I mentioned the MC-E solely because it would be more efficient to run MC-E at the required power to produce, say 150 lumens, than a single XR-E. This is because the current is split by 4 so the forward voltage of each die would be slightly lower. 

In your above scenario, you have to consider that you are dumping more than 10W of energy into either a single MC-E or four XR-E emitters, even if they are mounted to a large heatsink (1A per emitter or die means around 14W total according to jtr1962's measurements). At these higher power levels, then the way that heat is concentrated means everything.

However, if you consider the scenario in your other thread where the tiny heatsink/heatspreader (1" dia by 0.5" deep) can barely handle more than 3W, then the effect of dumping 3W into a MC-E will have little difference compared to doing the same with 4 XR-E emitters (the effect is not as dramatic). The heatspreader will struggle with dissipating nearly 3W of heat regardless to how the heat is concentrated by the emitter(s). Either of the two types of emitters will be running hot at 3W mounted on a heatspreader that is nearly saturated with heat.

Sorry that I am tying these threads together, but I just want you to make sure you understand the difference. If you are thinking about another project idea, then ignore this post. 

-Tony


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## yellow (Jul 3, 2009)

while it is now clear, that the basic question has the 4 XR-E "win", 
lets look at why the MC-E/P7 is used mainly now:

cost, difficulty of production, size
with just one quad, You save mounting+focusing of three additional led.

You have to find Your tradeoff!
(f.e. with a nice, thick aluminium mounting plate and a smaller housing, the quad also works nicely)


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## saabluster (Jul 3, 2009)

yellow said:


> while it is now clear, that the basic question has the 4 XR-E "win",



Sorry but I disagree. The answer to the OP's question "1 MC-E vs multiple XR-E which needs *more* heatsink?" is XR-E. Even if we assume there are 4 XR-Es to the one MC-E(best case senario) the MC-E still wins. If the exact amount of power is going to all the dies the MC-E dies due to the current density will be running hotter and therefore their Vf will be lower and it will be more efficient from a power standpoint. Therefore it will make ever so slightly less waste heat. That means the XR-Es needs more heatsink. However if the question had been which needs a _better_ heatsink than the win would go to the XR-Es.


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## lightime (Jul 3, 2009)

Tony, thanks for chiming in again...you have been very helpful and I appreciate it very much. I am still going with what we decided in the other thread for that application. Now I am just trying to figure out other applications where I can use this type of emitter. By the time I'm done I will probably have them all over my house, shop, and cars!!!!!!!!!!

So the other application in the car with the space constraints will still be using the single XRE we talked about, most likely with 700 or less mA.  BTW, I would still be interested in your input on the other thread regarding the optimum vs easiest way (I know there will be some trade off) to drive that single XRE in the other thread.



Gryloc said:


> Hey there again! So, yes 4 XE-E emitters are better than 1 equally matched MC-E. I just wanted to poke in to tie this to your other thread, lightime. I mentioned the MC-E solely because it would be more efficient to run MC-E at the required power to produce, say 150 lumens, than a single XR-E. This is because the current is split by 4 so the forward voltage of each die would be slightly lower.
> 
> In your above scenario, you have to consider that you are dumping more than 10W of energy into either a single MC-E or four XR-E emitters, even if they are mounted to a large heatsink (1A per emitter or die means around 14W total according to jtr1962's measurements). At these higher power levels, then the way that heat is concentrated means everything.
> 
> ...


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## John_Galt (Jul 3, 2009)

This has been a question I have been pondering over for my various designs for bike lights, etc. How does one calculate how much heat dissipation you need from various sources? And is there an equation of the amount of surface area needed to dissipate a certain level of heat? Please give me more time, I have more questions, and have to switch computers momentarily...


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## Marduke (Jul 3, 2009)

John_Galt said:


> This has been a question I have been pondering over for my various designs for bike lights, etc. How does one calculate how much heat dissipation you need from various sources? And is there an equation of the amount of surface area needed to dissipate a certain level of heat? Please give me more time, I have more questions, and have to switch computers momentarily...



No real easy formulas since every problem is unique, but you can start with a free online thermodynamics book of your choosing.


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## SemiMan (Jul 4, 2009)

Lot's of guessing and NO ONE reading the data sheets!

MC-E: 3C/Watt

XR-E: 8C/Watt

MC-E has 4 die, so that 3C/watt equates to 12C/watt per die. If you are running each die at 2 watts, then each die is going to run 8celsius higher.


In terms of basic heat transfer, 4 XRE will also have an advantage assuming they are spaced out. The 4 XRE will have greater cross-section to spread heat into the heat sink. If the heat sink is highly conductive, i.e. thick copper, then the advantage may not be high. However practically, I could see another few C/watt advantage for the 4 XRE.

Easy advantage to 4 XRE. The biggest advantage is just at the package though.

Semiman


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## saabluster (Jul 5, 2009)

SemiMan said:


> Lot's of guessing and NO ONE reading the data sheets!


I wasn't guessing. If you check the data sheets you will see that the Vf of the MC-E is already lower than the XR-E. Now factor in the higher die temps of the MC-E which reduces the Vf even more and you will find that it takes less energy to power the MC-E than the XR-Es as the MC-E is more energy efficient. Less energy in= less heat out. Now go back and reread the OP's question. The answer to that question is XR-E not MC-E.


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## yellow (Jul 5, 2009)

the majority of ppl not necessarily must be right,
but in general it is



while besically there might be a tiny - measureable - difference speaking for the MC-E, it remains that its four dies are backed on such a small space, that the thermal plate MUST be considerably thicker to get the heat away there, while the single emitter ones are spread and nearer to the housing.
Do You build/mod You led lights? (as most other posters do?)


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## saabluster (Jul 6, 2009)

yellow said:


> the majority of ppl not necessarily must be right,
> but in general it is
> 
> 
> ...


 I am being rather pedantic I know but the OP's question was about which needs _more_. Everyone has given answers based on what would be a much better question. "Which one needs _better_ heatsinking?" That is what should have been asked.



yellow said:


> Do You build/mod You led lights? (as most other posters do?)



I am OMG Lumens. See my sig line.


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## yellow (Jul 6, 2009)

I have to admit my english might no be good enough to understand the difference?
:thinking:


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## lightime (Jul 6, 2009)

Isn't it the same question from a different perspective? I want to know which needs less heatsink because I am limited by space. Whichever one needs less leaves the other one needing more or "better" as you say 




saabluster said:


> I am being rather pedantic I know but the OP's question was about which needs _more_. Everyone has given answers based on what would be a much better question. "Which one needs _better_ heatsinking?" That is what should have been asked.
> 
> 
> 
> I am OMG Lumens. See my sig line.


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## saabluster (Jul 6, 2009)

lightime said:


> Isn't it the same question from a different perspective? I want to know which needs less heatsink because I am limited by space. Whichever one needs less leaves the other one needing more or "better" as you say


As I see it.

More=quantity 
Better=quality

More "can" be better but not necessarily. The outside of your light can only shed so much heat for a given set of conditions. You could add _more_ metal on the inside to extend the amount of time the light could be on before overheating the LED or you could improve the _quality_ of the materials used. Improving the quality can allow you to run the exterior at higher temps while still keeping the die temps low enough. Just adding more of a lower quality material will not appreciably add increased steady state performance but can increase short term performance.

You say you are limited for space. I am not familiar with your application but if your limit is one of of diameter I would go for the MC-E. If it is of depth go for the XR-E.


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## Frozen (Jul 7, 2009)

I have 3 bike lights, each made by two DX housing sku.13741. The first one is driven by quad XR-E R2 and two are MC-E from Cutter. Design, driver Maxflex, battery, and other materials are almost same.
Quad R2 run 1 minute longer (5'30'') than MC-E before Maxflex get 60°C and switch to low mode.


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## SemiMan (Jul 10, 2009)

The difference in forward voltage is 0.1 volts approximately at typical operating currents, so call the typical forward voltage at 700mA 3.4 volts. The MCE has an advantage of 0.1/3.4 or roughly 3%.

In a typical flashlight, with each die running at 2.5watts, I likely want my thermal resistance to be on the order of 40C/watt or less. We could even call it 50C/watt or less.

The XRE has a 4C/watt improvement in thermal resistance. That gives it an advantage of 4/40 or 4/50 or somewhere in the 8-10% range or far better than any small reduction in forward voltage.

The increase in die temperature, 10C max on the MCE is only going to reduce the die voltage by 20-30mV, so maybe that 3% goes up to 4%, but since it is a closed loop, the effect is less. 25% of the energy going in is converted to light, but since the efficiency difference is at best slightly better for the MCE due to the low forward voltage... so I would be maybe at 3.5%*(1+3.5%).... want to call that 3.6% ...heck call it 4.1%.

Anyway you look at it, for the same overall heat sink, the 4XRE die will be running at a lower overall temperature. As one designs thermally to either minimize die temp to maximize output and life, and other designs for minimum heat sink for a given die temp, the 4XRE wins just based on bulk heat sink.

A practical implementation means the 4XRE will likely have a better thermal path to the bulk heat sink which means that the 4C/watt advantage may actually be 5-6C/watt or possibly 15% which will be vastly better than the MCE implementation. Let's not forget the 4XRE have a larger IC to board bonding areas so in most practical implementations that may be another 1C/watt or more... so now we are at 6-8C/watt.... getting up there on 20%.

So my analysis stands, the MCE will require more heat sink, and/or the XRE will require less heat sink to meet a maximum die temperature specification at a given current drive.

Semiman


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## saabluster (Jul 10, 2009)

SemiMan said:


> So my analysis stands,


And so does mine. I purposely left open that side of the argument just because I wanted to see your comeback. And I'm lazy. As a matter of fact there is quite more to be argued in favor of the XR-Es. As I mentioned before my point was to answer the OP's question and since everyone was jumping on the XR-E only bandwagon I thought I'd side with the poor helpless MC-E . I agree with most everything you said but it is always fun to be the devils advocate. We are both right depending on the conditions and variables, the end goals from a design perspective, and depends as well on the definition given to some of the terms. I do concede that the XR-Es win in the vast majority of circumstances. But not all.


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## SemiMan (Jul 11, 2009)

Someone doubles as a politician.......


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## saabluster (Jul 11, 2009)

SemiMan said:


> Someone doubles as a politician.......



I did *not* have sex with that woman!


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## csshih (Jul 11, 2009)

saabluster said:


> I did *not* have sex with that woman!


 
That's what _they_ all say.


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## WeLight (Jul 11, 2009)

My 2cents worth, caus I found two and it dont buy anything else

The MCE, M bin at best is a Q4 emitter x 4 so its already behind the eight ball, it uses a leadframe as part of its heatsinking model and does not sink the same way as XRE so it becomes difficult to compare. As a package it has some marked improvement over XRE in terms of density and if you could get 4 XRE die as close together you would still have Q4 vs R2 as a comparison so certaintly MCE will require more heatsinking just on comparable efficiency


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## saabluster (Jul 11, 2009)

WeLight said:


> My 2cents worth, caus I found two and it dont buy anything else
> 
> The MCE, M bin at best is a Q4 emitter x 4 so its already behind the eight ball, it uses a leadframe as part of its heatsinking model and does not sink the same way as XRE so it becomes difficult to compare. As a package it has some marked improvement over XRE in terms of density and if you could get 4 XRE die as close together you would still have Q4 vs R2 as a comparison so certaintly MCE will require more heatsinking just on comparable efficiency


The M bin MC-E is 430 lumens at 350mA per die. Divide that by four and you get 107.5 lumens per die at 350mA. That means the MC-E dies at minimum are averaging ever so slightly above Q5 minimum spec. That and the OP's question was comparing Q5 binned XR-Es. Still thats a good point. You could just as easily use R2s instead of the Q5s.


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## lightime (Jul 13, 2009)

Thanks SemiMan for the great explanation. I wanted to thank everyone for all their input. Tons of great info here. Very much appreciated folks. :bow:

Now it's time for me to start applying it. I have a bunch of Q5 XRE's and even a couple MCE's coming for me to mess around with. MANY more questions will follow


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