Crash-testing a XM-L2 and a XP-G2 on copper Sinkpads

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djozz
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Crash-testing a XM-L2 and a XP-G2 on copper Sinkpads

I promised that I was not going to do more testing on bare leds because I do not have the equipment to guarantee accuracy of the numbers.....

Ok, one more then, because I am really curious what the limits are for copper-mounted leds (mounted well and heat-sinked well), I can not find anyone who had tested that before, and as a modder I just want to know that .

I borrowed a bench power supply from work that can deliver up to 40A and decided to sacrifice a XM-L2 and a XP-G2. I had bought those before the nice neutral bins became available and they were not going into any flashlight anyway.

When I have more time I will put the results in nice graphs, for now you will have to do with two video's and my comments on them.

EDIT: I made the graphs, with some comments, see post #51

The first video is a test on a XM-L2 T6 1C bin (I believe I bought it from cnqg), reflowed on a 20mm Sinkpad, with a 49mm reflector on top to be able to do ceiling bounce lux-measurements. The set-up is similar to the MT-G2 test and the Nichia219 test I did recently, but with a different power supply. The left reading on the power supply is the output voltage (this voltage reading appeared to be a bit wacky, in the second video I added a separate voltmeter measuring directly at the led wires), the right reading on the power supply is the current going through the circuit (and therefore, the led). Again everywhere very thick copper wiring to minimize losses between power supply and led, and lots of aluminium under the Sinkpad to maximize heat sinking. Lux was measured 76cm from the ceiling, for a lumen estimate OTF of the reflector the lux-value that can be seen in the video should be multiplied by a factor 2.06. I forgot to put a glas lens on top of the reflector, to get a OTF number that includes a non-coated glass lens substract a loss of about 5.5%.

 

 

Second is a video of a XP-G2 R5 0D bin (from Fasttech I believe), mounted on a 20mm copper Sinkpad, with a 20mm reflector and a cheap AR-coated lens on top. I took a picture of the led-situation Smile:

As mentioned I added an extra volt-reading, to avoid confusion, here is what can be seen on the video:

So here's the video:

 

Discussion of the video's:

The first thing I wanted to know at what current and how the leds were going to blow. The answer is somewhere between 8.5 and 10 amps. This particular xp-g2 led could even handle a bit more current than the xm-l2, but I guess it will differ a bit between individual leds. Both leds just went dark when blown up, no turning blue or flashes or anything. A close look at the fried leds show in both cases damaged silicone around the bond wires suggesting those were burnt through. The emitting surfaces look undamaged, I guess the heat sinking on Sinkpads is so good that both in the xp-g2 and the xm-l2 the bond wires are the first to go, not the die. And because (it looks like) the thickness of the bond wires of the xp-g2 and the xm-l2 is the same, the current at which they burn through is about the same. Pictures of the fried xm-l2 and the xp-g2 (same magnification):

So what else can be seen in the video's.

Well, the maximum output for the xp-g2 is reached at about 6 amps, but there is hardly anything gained anymore above 5 amps, I measure a 'OTF' number of about 880 lumen at 6 amps (I have no integrating sphere, so I can not measure bare led lumens, but these 'simulated OTF' numbers do give an idea of what can be achieved in an actual flashlight).

The output for the xm-l2 increases without topping off right up to the current at which the led is fried, so the maximum output of the die of the led is not reached when the bond wires burn through. For us 'flashlight devotees' the xm-l2 could do with some thicker bond wiring! The maximum output (for what that is worth so near to the fatal current) is about 1870 'simulated OTF' lumen (in the situation with a non-coated lens on top of the reflector). It is 1630 lumen at a 'safe' 6A. Output is of course a bit better with a quality reflector and lens.

I haven't discussed the voltage readings yet. It looks like they more or less match the numbers measured by Match, only my Vf-measurements of the xp-g2 at the higher currents are significantly higher than Match's numbers. Could it be that his Fluke was faulty already then??

That's it for now, when I have time I will put the data in some nice graphs (EDIT: done that, see post #51). Until then I hope the video's will do. Thanks for reading.

Edited by: djozz on 06/24/2013 - 19:27
mattthemuppet
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awesome! There’s nothing a bit of science that’s both informative and destructive at the same time! I wonder if you dedomed those LEDs and bridged the bond wires with a dab of solder they’d work again? Might be fun to try out if you have some spare time Smile

djozz
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mattthemuppet wrote:
awesome! There's nothing a bit of science that's both informative and destructive at the same time! I wonder if you dedomed those LEDs and bridged the bond wires with a dab of solder they'd work again? Might be fun to try out if you have some spare time :)

I tried to repair a broken bond wire once on a dedomed xpe going wrong and I found it impossible to do. But well, these leds are a bit bigger so I'll give it a try Smile, just dumped them into some Coleman Fuel:

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Very interesting. Thank you for doing this test and reporting.

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You Sir is awesome Smile

 

Thank you for this!

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zeremefico
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Nice test!
In the title, I think it should be “an XM-L2”, with ‘n’.

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zeremefico wrote:
Nice test! In the title, I think it should be "an XM-L2", with 'n'.

Only if the letter X starts with an E! Silly

jmpaul320
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those are some really interesting numbers – sinkpads go along way Smile

Would you mind keeping the wrong flashlight?
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Thanks you very much for this info. It was exactly what I have been looking for. I’m planning to spend next months flashlight budget on direct copper bonded emitters and I really was interested to see how far I could push them and at what point I would see diminishing returns as well as failure.

Excellent information and timely too. Smile

I’m a junky, I mod lights so I can sell lights so I can buy more light to mod so I can sell lights to buy more lights to mod.

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Thanks for starting the next round of discussions and for the effort in doing this for the membership. Cheers.

 

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relic38
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Excellent work djozz! Looks like direct-bonding emitters will allow 6-7A drive for flashlight use. I’ve had a few running in the 5.5A territory with no issues. Looks like the die itself is very safe.
Anyone got (access to) a wire-bonding machine? J)

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texaspyro
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relic38 wrote:
Anyone got (access to) a wire-bonding machine? J)

I sold mine a few years back. It had a really nice microscope on it…

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Would be nice to rebond dedomed emitters for 8-9A operation J)

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Thanks djozz for the information!

My gratitude to those who are willing and able to help others (in whatever way you can)! Being human is more than just existing for yourself. Smile

comfychair
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I've resoldered a XPG2 die back onto the substrate, but never tried to mess with the bond wires...

bdiddle
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Care to try an XML? I wonder if the three wires will raise the ceiling…..

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Why are your PS and DMM voltage measurements off by a volt?

Nice testing, thanks for your efforts! Smile

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DENGOH
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What an experiment. I am more confident to do 3A for XPG2 now. Thanks.

cool i'll see you when you get there

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Awesome test! Very informative djozz. I wonder what would happen if you stuck a piece of dry ice under the heat sink Shocked

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holy cow.

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DENGOH wrote:
What an experiment. I am more confident to do 3A for XPG2 now. Thanks.

Yes.

Tonight I stuck an XPG2 neutral on a Noctigon inside a Sipik 68. I replaced the driver with a Nanjg 105c with 3 extra regulator chips attached for 4 amps total, running on IMR 14500.

It’s bright, but unfortunately, the focal length is wrong for the new star. I’ll need to file down part of the outside of the pill in order to make it focus properly.

djozz
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ryansoh3 wrote:
Why are your PS and DMM voltage measurements off by a volt? Nice testing, thanks for your efforts! :)

 As said, the volt reading of the power supply is a bit wacky, in the video it is too low for a while when the actual voltage is higher, then suddenly starts displaying a correct voltage for the rest of the experiment.

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Whoops, sorry missed that part. Smile

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Nice. Thanks for sharing. Looking forward to graphs..
I killed an XP-G2 yesteday. Mounted on 20mm Sinkpad attached to a large piece of aluminium. It was de-domed. About 5A and it was dead. Instant kill.. Silly (no worries only a cheapo CW from FT)
Im pretty sure others have used them at that current. Id guess my de-doming job had weakened one or both wires (a bit strange since I don’t touch them and never had issues with de-doming in the past).

I have a driver (from STL- V6) that I can easily resistor mod from about 2,8-5A as I wish.. Modded it to 4,7A yesterday, but did not to dare try it on an XP-G2 after I had fried one at 5A with another driver. Dialed it down to 3,7A just to keep it moderate. 0:) Im already feeling inspired to go higher now.. J)

Do you think emitters are killed more easily if they go from cold to instant high amps? Im a bit surprised they managed all those amps, especially the XP-G2.

Do you feel like doing MT-G2 if you get some funding from several members?
Ill donate 2,5 bucks for the sake of science (killing and MT-G2 and getting some numbers out of the process). Im sure some other members would contribute too.
Or maybe just contact Hank (IOS) and see if he is feeling generous. 0:) Worth a shot…

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RaceR86 wrote:
Do you think emitters are killed more easily if they go from cold to instant high amps?

What do you mean by cold? 20-25C (room temp) or 0C. You want to thermally shock the LED?

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Room temperature…

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Slim Pickens
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I wonder how an LED like the Luxeon T would perform on a Sinkpad board.

djozz
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Slim Pickens wrote:
I wonder how an LED like the "Luxeon T":https://www.google.com/url?sa=t&source=web&cd=1&ved=0CDQQFjAA&url=http%3... would perform on a Sinkpad board.

I'd love to see the Luxeon T for sale on a Sinkpad, it seems excellent for flashlight use and I understand it has very low internal thermal resistance. It is just that it has a very different solder pattern and needs its own Sinkpad.

djozz
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RaceR86 wrote:
Do you feel like doing MT-G2 if you get some funding from several members? Ill donate 2,5 bucks for the sake of science (killing and MT-G2 and getting some numbers out of the process). Im sure some other members would contribute too. Or maybe just contact Hank (IOS) and see if he is feeling generous. 0:) Worth a shot...

I have been thinking about it, but apart from the costs I only have one at the moment and I have other plans with it. Maybe later.. (or someone else Innocent)

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I would like to see an MT-G2 being fried too:) and would like to donate some money toward the emitter as well.

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They don't pop or even turn blue at 9 amps, though based on my one sample I can't say it puts out more light at that much current.

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