I was ordering a few parts and saw that Mouser also happened to have the newish Lamina Atlas in stock. I figured I'd pick one up and see what it's made of.
The Atlas is basically an improved version of the BL-4000. It's spec'ed to output more than the BL-4000, with improved efficiency. Let's check it out:
Here it is next to what it competes with in terms of specs - the Luxeon V star. They are about the same size. Both use a quad-die, series-parallel configuration, resulting in nominal current level of 700mA, and typical Vf at that current level in the 7V-ish range. If you're familiar with the BL-4000, then a couple of differences are immediately apparent. If not, here's a picture of the BL-4000 so you can compare:
The Atlas has a silver ring around the optical dome (which is made of clear silicone). The optical dome is also substantially taller. This ring may be to allow optics to rest on the Atlas without the risk of damaging the part, and the taller dome may improve performance with certian optics as well. Finally, you can easily see the individual dies of the Atlas, so it appears that they are also using a conformal phosphor coating, which provides better off-axis color quality.
You can see how widely spaced apart the dies of the Atlas are, especially compared to the tightly packed dies on the Luxeon V. This will mean that the Atlas will not focus well in normal sized reflectors - if you thought the "donut-hole" problem was bad with a Luxeon V, it'll be much worse with the Atlas.
Here is a close-up of the 4 dies with only fractions of a mA of current flowing:
Close up of the two top dies:
You can see that each die is using two bond wires on each contact. There are no less than a dozen bond wires holding things together electrically. In addition, you can see the top contact pattern on the LED dice. This contact pattern is unlike any I've seen so far between all the LEDs I've worked with, including the XR-E/Seoul P4, Luxeon I/III/V, or K2/Rebel. It would be interesting to know who they're sourcing their dies from.
Let's see what this thing's made of...
First, beam profile:
Pretty average beam profile. From a distance, pretty much equivalent to a Luxeon V. Of course, up close things will be substantially different.
Here's the raw performance data:
Next, the Vf curve:Code:Current (mA) 0.1 30 130 310 670 980 1260 --------------------------------------------------------------------- Vf 2.5* 5.29 5.79 6.32 7.08 7.61 8.07 Watts 0.75 1.96 4.74 7.46 10.17 Lumens 49 106 193 248 285 Lumens/W 65 54 41 33 28 *No light was produced, which is unusual. Every other LED produces some small amount of light at this current level. The low Vf is probably a result of current jumping across the junction without actually producing light.
The series-parallel arrangement already assures a Vf higher than the single-die devices we're used to. However, these dies don't maintain a low Vf very well at higher current levels. This significantly reduces efficieny at higher current levels.
Next, luminous output:
While the Atlas is outputting more at a given current level than these other LEDs, keep in mind that it (like the Luxeon V) requires twice the voltage and thus twice the power to do so. So while the output might seem good, the efficiency really isn't that great. I've had poor luck with Lamina products taking high levels of overdrive without suffering damage, so I didn't bother pushing it past about 1.2A.
The Atlas is hanging out in Luxeon V territory for efficiency. Notice the efficiency dropping off faster than a Luxeon V at higher current levels. This is due to the Vf which increases dramatically at higher currents, vs. a Luxeon v who's Vf stays relatively flat as current increases.
The efficiency of the Atlas drops of a lot more than comparable LEDs. Even the Luxeon V maintains its efficiency much better. And when you consider that each die of the Atlas is receiving only half the current of the single die LEDs (like the Rebel, XR-E, Seoul P4), you can see that the dies in the Atlas have a pretty big performance deficit.
So, are they worth it? For me, no. The Atlas costs about $16, but only offers (at best) previous generation efficiency. The widely spaced quad dies in the optical cavity make it hard to focus in small reflectors. You can get almost the same level of output (close enough to not matter) from an XR/E, Seoul P4, or Rebel-100; each of which will be over twice as efficient, have a much smaller source size making optics and reflectors perform better, for less cost (even for the premium bins). Plus, the Atlas only comes as a "star", limiting the use in certian smaller form factor applications. We are also starting to see fierce competition in the multi-die, high output LED market from competitors like Edison Opto, Osram, and even Seoul, all of which offer higher output levels in the same package size, and better efficiency.