LED test / review
EN
Cree XLamp CXA1304 (9 V variant)
CXA1304-0000-000C00B40E1
In the meanwhile the market for LEDs is big – very big. There are many types and designs available, and not all LEDs are looking like that in our flashlights. Another big market are changeable LED bulbs and special high power modules for interior / exterior / large area lighting, downlights, and for this usecase there are COB LEDs (Chip On Board) used often.
COBs are not the same like the ‚classical‘ Lateral / Flip Chip LEDs we use in flashlights. These emitters must be soldered on a MCPCB / LED board, which is in turn mounted on a heatsink to ensures efficient heat dissipation. COBs doesn’t need a MCPCB, the LED dies are soldered directly on the substrate which is mounted on the heatsink directly.
Sounds like fun? Maybe! This test I had planned for some time and I always found that interesting to think about alternative LED (designs / technologies) in flashlights. So now I do not only want to test this LED, but also demonstrate the design and LED chip configuration and shows you how good such a COB LED performs in a flashlight optic.
And yeah, the classic overcurrent test is also included here. :)
Technical data
Tj 85 °C / If 400 mA
Order code: CXA1304-0000-000C00B40E1
Type: COB
Binning: 410 lm (457 lm @ 25 °C Tj)
Rated voltage: typ. 9 V (max. 10.5 V @ 25 °C)
Max. forward current: 1,000 mA
Viewing angle: typ. 115°
Color temperature: typ. 6500 K (color kit E1)
Thermal resistance: not specified in datasheet
Junction temp.: not specified in datasheet, Cree recommends a maximum LES temperature of 135 °C
I purchased this emitter at Mouser a few months ago.
You can find the official datasheet here (Cree website, pdf)
First appearance and LED chip
A COB does not look like the classic LED. The white substrate is square shaped and measures 13.35 x 13.35 mm (0.526 x 0.526 in). The so called Light emitting surface (LES) of the CXA1304 is 6.00 mm (0.236 in) in diamater, and the outer diameter of LES (white border) is 7.50 mm in diameter.
The marking ‚1304C‘ doesn’t exist on all CXA1304, though. Some of my other samples are marked, other not - like those in my teaser picture. The solder point left to the marking is needed for thermal sensor to measure Tsp (temperature solder point).
In general, the design and appearance of COBs are relatively equal to each other.
The whole LES is covered with yellow phsophor, unless well known LEDs like XP-G2 or XM-L.
Even without power the LED up the total of 12 single LED dies are easy recognizable.
Between the single chips the area lights up in yellow color which not does not represent the color temperature specified by manufacturer – a feature already known from newer Cree XLamp LEDs like XHP70 / XP-L2.
One of the LED dies is 1.00 x 0.65 mm (0.0394 x 0.0256 in) in size, so one chip is 0.65 mm² (0,0010 sq in) each, which amounts a total of 7.86 mm² (0.0122 sq in).
Behavior in optics
For this test I choose the reflector of a Nitecore SRT7 (first pic) and an unknown low-budget 1 x AA flashlight (second pic).
The single dies can be easily discerned, even in the reflector. At this point I expected a weird light pattern, and – yes, that was it.
The light color is not uniform, yellow and blue areas are visible and are very annoying if the light would be moved also on uneven surfaces. Also this problem is known from XP-L2 and other LEDs, too but these doesn’t show such a clear behavior.
To fix this issue, the use of self-adhesive film (d-c-fix or similar) or frosted lens is basically inevitable. To demonstrate this I used a piece of d-c-fix Milky static which was mounted in front of the reflector:
After this the beam quality and color consistency is greatly improved.
The yellow and blue spots disapperead, the whole light is mixed and the tint get close to the stated 6500 K. Unfortunately (for thrower fans) the beam ist extremely floody, and there is no throw at all.
All reflectors I testes were SMO. But the using of OP reflectors makes no significant difference, the ugly beam pattern is still there but at least something weakened. For some users it could might be ok.
Power and overcurrent capabilities
25 °C Tsp, unless noted otherwise
I mounted the COB package on the heatsink directly.
Due to missing 9 - 12 V LED tests I can compare this COB with the XHP35 HI (highest bin E2) only.
Within official parameters
- At 1,000 mA (max rated current): 1,024.0 lm @ 10.77 V
- Power at rated maximum: 10.77 W
- Efficiency at 1,000 mA: 95.1 lm/W
- At 400 mA (binning current, but 25 °C Tsp): 538.0 lm @ 9.43 V
Overcurrent:
- Maximum at 1,750 mA (1,289.3 lm @ 12.23 V)
- Power at maximum 21.40 W
- Sweet spot at 1,200 mA (1134.7 lm @ 11.18 V)
- Power at sweet spot 14.36 W
- Efficiency at max 60.2 lm/W, in sweet spot 79.0 lm/W
Interesting facts
- In power profile, this COB performs like a XM-L2 / Osram Oslon Square. The power dissipation is almost the same as mentioned emitters. The die size is almost the same.
- The XHP35 HI has much more power! It almost reaches their 3,000 lumens at max 3.00 Amperes, at 15.14 Volts.
- The possible gain of the CXA1304 in light flux is negligable overall. The light flux just rises by 265.3 lm (approx. 20 percent). The reason for this could be the (low / mid power) dies which aren’t suitable for high power LEDs.
- At maximum current, one of the twelve dies delivers around 107 lumens of light.
- I do not recommend to drive this COB above the rated maximum current.
- The Vf of the CXA1304 reaches it’s 12 Volts. In some special cases it might be possible to drive this COB with (boost) driver to use with 12 V LEDs but also 9 Volts.
Now it gots weird.
The official Cree binning B4 for the CXA1304 states a light flux of 410 lm at 85 °C Tsp. For 25 °C measurements, this value is approx. 13 percent higher. In my test however, I got 538.0 lumens (!) at 25 °C Tsp. This equals to 476 lumens at binning conditions and this means also that the bin of my samples is also higher than B4, but C4!
So the thread title should actually be ‚CXA1304 C4‘ and not B4. ;)
I double-checked this result with some other COBs of same series, but other color kit and bin, and these LEDs follow the stated manufacturers specs. LEDs other manufacturers have also expectable results.
Maybe I got higher binned emitters erroneously, because of a mistake by packaging at Mouser? My test procecdure is reliable and proven and the results are congruent, in almost 40 measurements with the most different emitters. Some time ago with the XHP70.2 (English test in TLF here) I experienced the same phenomena.
Conclusion
I started this test with the question that COBs are usable in flashlights at all. The answer is: in principle yes, but… - with some very big compromises.
First, the package size is a problem. The most flashlights expects round MCPCBs, so the COB case has to be modified to fit in a flashlight correctly. A really important and problematic thing are the missing (custom) flashlight driver to power such an LED. Maybe the use of driver for 12 V LEDs (XHP35) is possible for this LED, but I hasn’t tested this yet.
The overcurrent possiblities of the CXA1304 are limited. The increase in light flux was only around 20 percent, despite my very good heat dissipation of my setup.
On the other side there are some very interesting COBs available with very unusual spectral bandwidths, like the Lumileds COB with Fresh Focus technology (specialized for lighting up certain food like fish, meat or bread, unfortunately the Vf is very high). Of the CXA1304 there is also a CRI min. 93 variant available, with nominal CCT 5000 K. With this LEDs in principle it’s possible to build portable lights with ultra high power AND light quality.
Use COB in flashlights?
Pro:
- Very special spectral characteristics possible
- Very high light quality at big amount of light possible
- With some COB series extremely high light flux possible
- Nice floody beam patterns possible if using certain optics
Con
- Size not suitable for flashlight
- in most cases changes in flashlight construction necessary
- In most cases very high Vf (more than 28 V are widely common)
- Not suitable to use in overdriven state (Hint: not sure, because I have only the CXA1304 tested!)
- Special electronics needed
I hope you enjoyed this 'test' and explainations. :)
Greetings, koef3
Mistakes and suggestions are best sent via pm.