2024-02-25
The SST-12 was tested about half a year ago. In contrast to most other emitters in the low-power class, this LED has an LED chip with a round luminous surface.
The Luminus SFT-12 has only recently become commercially available. In principle, the SFT-12 is an SST-12 without a dome. However, as with most Chinese emitters, there is no precise information or data sheet for the SFT-12. The test will show exactly how this LED performs in comparison.
The emitter was purchased from Kaidomain in January 2024 and was provided by BLF user @1stein. Many thanks for that!
Tj --- °C, If --- mA
- Type: single die, lateral
- Bin: F4 (?)
- Color group: BC (?)
- CRI: 70
- Rated voltage: — V
- Max. Forward current: — mA
- Max. Peak current: — mA
- Viewing angle: — °
- Thermal resistance: — K/W
- Max. Temperature Tj: max. —°C
Important note: An official data sheet is not available. Information in the course of the test is taken from Kaidomain’s product description and may therefore be incorrect.
The design of the SFT-12 is similar to many other Luminus emitters. The white silicone around the yellow illuminated surface is also surrounded by a metal rim, although this is silver-colored instead of gold.
There are two bonding wires which ensure the connection of the anode. In contrast to the ‘YLX N3535B’, which can be found here in the test and possibly uses the same LED chip, the SFT-12 only has two bonding wires, although the LED chip has contacts for four bonding wires. However, the pattern on the luminous surface is different on both chips, which could indicate that the round chips are made by different manufacturers.
The footprint is fully compatible with XP and 3535 boards, but the individual contact surfaces protrude clearly from the gray substrate, which also applies to the thermal pad. This results in a supposedly “poor” soldering with “gaps”, although the LED is firmly seated on the LED board (see also the picture of the LED on the side). The cathode is marked with a notch in the thermal pad.
Such significant reductions in the heat dissipation surfaces should be viewed critically; they further reduce heat dissipation, which is already severely limited, especially in the compact 3535 format. A marking on the top or a beveled corner of the anode connection is more advisable here.
The round illuminated area is surrounded by a strange yellowish ring, which is presumably caused by phosphor applied to the side or light escaping from the side. The white silicone is opaque and should therefore improve the optical properties when using secondary optics.
The luminous area is 1.27 mm² in size. The name SFT-12 refers to the size of the illuminated area. Due to the weak light emitted from the side, it is very difficult to determine the exact illuminated area and is subject to uncertainties.
Within official parameters, as far as known:
- at 1,800 mA (official maximum current): 605 lm @ 3.22 V
- Power at official maximum: 5.8 W
- Efficiency at 1,800 mA: 104.4 lm/W
- Maximum reached at 5.0 A, at this point 1070 lm @ 3.89 V
- Power at maximum 19.5 W
- Efficiency at maximum 55.0 lm/W
Due to a lack of official information, the data from Kaidomain (peak current 1.8 A) was used for the official maximum values. It is therefore not possible to guarantee the accuracy of this information.
Interestingly, the maximum performance of the SFT-12 is significantly better than that of the previously tested SST-12, possibly due to lower thermal resistance. Due to the higher maximum current, the luminous flux is higher, by around 30 %. Otherwise, the characteristic curve essentially follows that of the SST-12.
The ‘YLX N3535B’ outperforms the SFT-12 by a huge amount. The Vf is also considerably lower. This is probably due to the use of 4 bonding wires and possibly to a different LED chip. Due to the higher luminous flux of the N3535B, its luminance is much higher. The 95 CRI ‘Yinding 5050’ LED is out of competition in terms of its size and significantly larger illuminated area, but despite its excellent light quality it can easily set itself apart. The Vf of this LED is also quite low.
Compared to other round-die LEDs, the SFT-12 definitely still offers potential for improvement, particularly by reducing the thermal resistance.
Data for 25 °C Tsp (at 85 °C the luminance values are around 13 % lower).
The luminance is high, especially compared to other (larger) domeless LEDs. However, the SFT-12 is nowhere near the luminance of the ‘YLX N3535B’, which is used in the Wurkkos TS12 and can convert its significantly higher luminous flux directly into higher luminance. However, the SFT-12 is ideal for small throwers where excessive current is not practical.
The beam in reflectors (SMO and OP) is perfect. There are no artifacts due to the round illuminated surface. Rings can occur depending on the reflector used. These no longer occur in OP reflectors anyway. There is no annoying tintshift.
The SFT-12 tested here is green. With a duv of almost 0.007, it is outside the ANSI color space normally used for the color binning of LEDs. As the operating current increases, the duv decreases, but the green tint is still clearly recognizable, depending on your own perception.
The spectrum corresponds to that of an LED with a typical 70 CRI and reveals no surprises. This LED is not suitable for applications where high color fidelity is required. The CCT is in the expected range of around 6500 K.
- Ra: 71
- R9: -35
- CCT: 6619 K
- duv: 0.0069
The SFT-12 offers good performance for throwers in the low to mid-power range. The light pattern is perfect, there is no tintshift. The Vf is quite high, although this is also manageable with classic linear drivers.
Less pleasing is the green light color and the lack of any official information. This LED is listed by dealers without providing any official information or publishing a data sheet.
It also shows once again what a good LED the ‘YLX N3535B’ (test here) from the Wurkkos TS12 is. If this LED were available, my recommendation would clearly go in this direction, the SFT-12 simply offers too little power.
Pro
- acceptable overcurrenting results
- very good beam
- standard XP/3535 footprint
Neutral
- Vf could be lower
- relatively high thermal resistance
Contra
- green tint
- no reliable information on the LED publicly available (as of Feb. 2024)
- only available in China or from Chinese sellers
Thank you for reading the test. 
