Cree XD16 measurements

Those DIY board is very similar to my “twig-light”.

Based on my research with Jensen567, I predict the performance would likely to get worse in tight packed array.
E21A designed with sidewall reflector to minimize photon cross talks, big problem in general luminaire when one need to put arrays in very tight space. Even with those side wall reflector, I couldn’t close the gap narrower than 0,3mm. This phenomenon was urban legend to me until all those measurements revealed the ugly truth.

This XD16 doesn’t have any barrier (hence the blue side spill), the cross talks could be even more severe. I guess you’ll get increased luminance at the expense of much lower current capability. This should not be a problem if throw is what you’re after (hopefully it can beat the black flat). As long as the luminance gain vs. max. current net to useful numbers.

Let’s hope we have something better than XPL HI. I’m really curious about it too. Looking forward to see the result.

- Clemence

I’m not familiar with photon crosstalk. I looked at some of your tests. Do you just mean the edges are heated more and burn when two dies are next to each other? It seems to me that problem could be more to do with the construction of the E21A and it’s problem with phosphor cooling?

I don’t expect the XD16 to beat the black flat or XPL HI in luminance. I would expect up to a 15% increase from what I measured above, which doesn’t put it that high.

under the same setup the gapless design maxed in 4,8A (Jensen tested up to 5,5A). Spaced by 0,2mm made no difference. But using the alpha board spaced at 0,4mm it peaked very close to 12A.
250% max current increase.

No it’s not about phosphor cooling. Yes, the phosphor in E21A is indeed hotter than average but it still productive up to 3,2A/die. While in gapless quadtrix (4xarrays) max current was limited to only 1,2A/die.

- Clemence

This very well could be important for the XD16, but the extent of the effect is completely dependent on the chip design and phosphor heating. For example the edges of the E21A phosphor are probably more susceptible to burning because they are farther from the contacts leading to less cooling. I’ll keep it in mind during testing.

Thanks for the test! Interesting…

Could you explain what you believe is the mechanism causing this phenomenon then?

You’ll find most of the information here:

- Clemence

Interesting results but sadly about what I expected, in fact a bit better I would say. I only expected around 800 lumens max based on the info I had.

Although you also have a DTP mcpcb, which most could not do or use with flashlights. So expect performance to be worse in actual use with a normal mcpcb.

Sadly like many have said, not very interesting for flashlight use. Although I am surprised that it still suffers the tint shift issues, wasn’t that one of the big marketing points that it fixed the tint shift issues?

A single XD16 is not interesting, but a 2x2 or 3x3 array can have respectable performance (good output and no donut hole) with the possibility of being 3V. If my speculation is correct about the output going up by 15% upon making into an array then it can compete and even beat the XHP70.2 or XHP50.2. Of course the lack of proper MCPCBs would still limit the performance.

Are you going to run your set up in series or parallel?

If in series this would be similiar to the XHP35.

I’m planning a 3x3 array all in parallel. Should have a 4.8mmx4.8mm light emitting surface.

A progress shot of my 3x3 XD16 parallel MCPCB.

Interesting looking, and not simple lol.

I would say “simple, but not easy” :wink: :innocent:

Interested in seeing the results! Thank you for your contributions!!

Yes, simple but time consuming. :sunglasses:

I just placed the dies on to see how it will look. The copper is about 20mm in diameter. When I light it up with my DMM the contact is intermittent and only some dies light up because they are just resting there, but I can see there is good “light sharing” going on. The dies surrounding a lit die light up evenly just from the light that was escaping out the side when it was alone. So I’m hopeful about a nice boost in efficiency/output when these are in array form.

When Clemence tested this with the E21 they burned the edges of the LED’s, so at higher currents it could work in reverse.

Although apparently if you put some clear silicone over the entire surface and make it thin enough to go between the dies, it will fix the problem? At least I think that was the idea.

Interested to see how this turns out.

Whatever happens, I salute you for the effort! :beer:

Cool! I know Clemence’s prediction but nothing beats an actual experiment! :slight_smile:

Good job with the file! I know it’s very time consuming but let’s do it.
If you can bond those sides using any kind of optically clear silicone then the photon cross talks should disappear.
EDIT: with optical bridge most of the photons will escape to the adjacent LED without being bounced back to heat the die it exited before. I had the same thought but not many people would want to carefully glue each module by themselves. I decided not to continue with the gapless design for some reasons:

- Gapless design as is (with no post processing) limits the max. output (limited max current)

- Cleaning the flux residue requires special method which would not be easy task for most people, let alone mass production.

- Designed for Nichia E21A. Gapless vs gapped design beam profile don’t differ much. Donuts with either SMO/plain TIR optics.

  • Boost drivers are getting widely available

With XD16 higher output capability, you might be able to overcome what E17A/E21A can’t do previously.

- Clemence

Thanks guys.

I’m not too worried about excessive heating of the phosphor due to “photon crosstalk”. The E21A has exceptionally bad cooling of the phosphor, especially at the package edges. The edges of the E21A burned first even when it was operated alone, so it’s not surprising that a neighboring die would exacerbate the burning. I wouldn’t necessarily expect the same results with the XD16.

The “light sharing” that I observed with the XD16 in array form is a different phenomenon than the E21A “photon crosstalk”. The XD16 flipchip design has the die exposed at the edges so the unconverted blue light escapes from the sides of the clear sapphire/SiC. When in array form I suppose this light enters the neighboring dies through their respective exposed sapphire/SiC edges. This results in the entire neighboring die being illuminated practically evenly, not just the phosphor near the edge. The resulting light collection/conversion efficiency looks to be much improved compared to the lone XD16 I tested. I assume this mechanism is part of cree’s design.

I am, however, concerned with flux residue seeping up the cracks and causing burns on the surface. Any special tips for cleaning the flux residue?