Back when the XPG3 came out and we were trying see if the dedomed or sliced version had good performance, I was learning about the structure/architecture of LEDs better in order to understand the connection between dedoming and light recycling. See here for an explanation.
In this article , some details of different architectures are discussed. It mentions one strategy for increasing light extraction efficiency, light recycling, in which there is a reflecting silver layer below the LED junction. Photons that don’t escape the LED package are reflected down past the junction and reflect off of the silver layer, getting another chance at exiting the package. I think the luminance increase we see from dedoming has to do with this reflecting layer.
As we have noticed, there are some LEDs that don’t have bond wires on top. This is an architecture called “flip-chip”. Both the positive and negative contacts are on the bottom. My hypothesis is that the flip-chip style LEDs do not benefit nearly as much from dedoming as the traditional architecture with visible bond wires because of a difference or absence of the reflecting layer under the junction.
For example, the XP-G3, which is a flip chip style, did not have good performance when sliced or dedomed. The Nichia 219C which also is a flip chip style without visible bond wires also did not have good performance when sliced. The XM-L2, XP-L, and XP-G2 experience a ~1.9x increase in luminance upon dedoming, while the flip-chip style experience a ~1.3-1.5x increase. Another example is the third generation Oslon Square, which has visible bond wires. Although this LED is apparently difficult to dedome, user FmC has had some success, and the luminance increase is on par with the XPG2.
Well….we will test it for dedoming anyway, XPL wont be discontinued any time soon, and i am pretty sue there are more emitters to come from Cree, so dont give up hope
XPL HI can be dedomed too ( pretty easy though) and when they announce the XPL2 Hi version we will dedome it ( i hope easy again )
I tried a XPL HI dedome using ZEP Aerosolve II, after 18 mins all around the phosphor loosened up, but the shiny surface coating of the phosphor looked rock solid. On an older XM-L2, Aerosolve II popped the dome off in 12 minutes. This is my first time testing dedoming with this stuff, so dunno all the details (testing the LED, etc.), but it's a big time saver and lot less odor than gasoline.
I'll try it in a tuff LED, like a XP-G3 or XPL V6 0D to see how it does, but doesn't sound like it will work on them.
On the new XP-L2, reviewing the specs is somewhat disappointing - rated lumens is slightly less than XP-L specs at all bins, plus still listing "only" V6 as the max bin. Lower Vf is darn nice though, and "temperature coefficient of voltage" looks improved, which I think that means under heat, it will have less loss of voltage, therefore more output.
Careful look'n at those specs. I forgot where, but I think at Mouser, I went through all the available bin/tint offerings on the XP-G3, and this is also confirmed by offerings from other sources -- you pay the price in CRI for high bins, high output. The "tint" issue is getting more and more blurred. You can get high/max bin CREE LED's in neutral tints now, but the CRI is no better. Neutrals are available now in higher and lower CRI's, but the higher CRI's seem to always only be available only in lower bins.
You can't make assumptions anymore that warmer tints mean higher CRI - you have to carefully look at the full specs of the LED.
With the XP-G3 it took only a month or so before Cutter started selling a few 70CRI versions. and it took 3 more months for the 90 CRI ones hit the market. So with the XP-L2 perhaps you can expect a very limited selection soon
The search function does weird things every now and then, some very interesting threads never show up, even you search for the title literally. I think in the Google search there is a huge priority for often visited/edited threads, so if the thread you search for is fairly new, or is not visited often, and has keywords that resemble those frequently visited threads, it is never found, or sometimes as far as at page xx of the search.
Interesting, I am sure most of us will try one or 2 but beyond that I will wait and see how they perform before diving in. Not a big fan of domed LED’s period honestly but also hate dedoming. So XP-L HI’s are what I use almost exclusively.
The thing that bugs me about that dome the most is the poor quality color blending. Every Cree LED made in the past 8 years has had better color blending around the edges than what XPG3 has. Lower VF will be nice though I suppose.
EDIT: In fact the color rendering period with XPG3 has been poor in my opinion. Even the high CRI neutrals to me don’t look nearly as good as equivalent emitters from another series.