2025-11-29
- Type: single die, lateral
- Bin: G1
- Color group: BA-BB (6500 K)
- Voltage: 2.5-3.1 V @ 1,500 mA
- CRI: typ. 70
The SFT-42R tested here was purchased from Convoylight in mid-September. A data sheet can be found here.
In general the SFT-42R is similar to the SFT-25R. The biggest difference is the larger light-emitting area and the associated larger footprint. The metal frame on the substrate, familiar from many earlier Luminus emitters, has been replaced by a frame made of solid silicone, presumably to reduce manufacturing costs.
The chip is connected with 8 bonding wires. There is no clear silicone layer on the LED chip.
The LED measures 5.00 x 5.00 mm. Thanks to the familiar 5050 footprint, the SFT-42R is compatible with all standard 5050 boards.
The luminous area is approximately 5 mm2. Despite the 4.3 mm2 specified in the data sheet, the luminous area appears larger because the phosphor has been applied to a larger area than the LED chip and the light shines through the sides to some extent, which can be seen from the yellow edge. This reduces the luminance.
If the current is too high, the LED will be destroyed. This was the case at around 20-22 amps, although it should be noted that such high currents are unlikely to be reached when using a FET driver and an 18650/21700 due to the Vf. In this case, the phosphor layer burns and/or the bonding wires burn through, although this only occurs at high voltages. The LED chip is similar in design to the SFT-25R and other round-die LEDs.
- Maximum reached at 13 A, at this point 3339 lm @ 3.62 V
- Power at maximum 47.1 W
- Efficiency at maximum 71 lm/W
Data for 25 °C Tsp (at 85 °C the luminance values are around 13 % lower).
The SFT-42R is about as efficient as an SFT-70 with the same CCT and CRI. In addition, the performance of the SFT-40 is in a similar range. In principle, the SFT-42R is an SFT-40 with a round chip and slightly increased efficiency.
The Vf is quite high at over 3.6 V at maximum current, which should allow operation with direct drive FET drivers.
The round chip probably has slightly poorer heat dissipation, which could be due to the size of the chip – the maximum current is lower than for the SFT-40, despite the same footprint.
The luminance of the SFT-42R is very high, at least at maximum possible current. The SFT-40 has a lower luminance. At lower operating currents (3 A, for example), however, the SFT-25R or an LED with an even smaller luminous area is preferable as long as luminance and thus throw are important.
There are no surprises in the spectrum; the SFT-42R delivers typical cool white light with low color rendering. Typical YAG:Ce3+ phosphor is used.
The tint is greenish and lies just outside the ANSI color space, measured here at 350 mA. As the current increases, the duv decreases slightly, but there is no noticeable tint shift.
The beam is good and the SFT-42R can be used in reflectors without any problems.
- Ra: 69
- R9: -39
- CCT: 6855 K
- duv: 0.0057
The SFT-42R is the performance-enhanced version of the SFT-25R and is basically the same as the SFT-40, except that it has a round light-emitting surface. The beam is good and the luminance is high, at least as long as the LED is operated with the highest possible current.
As long as the slightly greenish tint and low color rendering are not relevant, this LED is perfectly suitable for higher-power throwers.
Thank you for reading this test. 
. Noteably, even at higher current, like Convoy M21E with