OSRAM IR SFH 4715AS + Luxeon IR short output test - Cu MCPCB vs. mosX

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led4power
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OSRAM IR SFH 4715AS + Luxeon IR short output test - Cu MCPCB vs. mosX

On BLF there are tests available for pretty much every white LED and even some UV/color LEDs, but I didn't see someone actually test IR LEDs, so I did short test of  relative output and forward voltage of OSRAM SFH 4715AS.

I used standard 1010 luxmeter which isn't the best choice for measuring IR LEDs, but if it's close enough to LED,it's able to detect IR light just fine. I can't measure absolute light output in mW with this luxmeter and method, only relative output (actual mW output vs. current still can be calculated from datasheet), but this is still very useful to see the limits of this LED.

Forward voltage was measured with 4-wire Kelvin method, to eliminate errors due to wires voltage drop.

I used two LEDs on two different MCPCBs; first one is non-DTP XP copper MCPCB mostly used for this LED among flashlight modders because it showed best performance:

https://www.fasttech.com/products/1611/10018154/3741200-20mm-copper-base-plate-for-cree-xp-series-led

OSRAM LED has footprint that's different form XP, but it still fits OK. Because ORSAM LED has thermal pad that is not electrically neutral, isolated MCPCB must be used.

Second MCPCB is mosX (short for MOSLED EXTREME), an aluminum board with thin ceramic (chemically grown aluminum oxide) as insulator:

https://led4power.com/product/mosled-extreme-mosx-ceramic-insulation-osram-oslon-mcpcb-20mm/

Footprint matches OSRAM LED footprint.

Test results are in table:

Lux values for second LED are scaled/corrected so that lux values are identical at low currents for both LEDs, this helps with comparing LEDs at higher currents. Correction factor is calculated from measurements at 0.4A and 0.6A.

Form test results it's visible that up to ~1A there is little difference in light output, but after that much lower thermal resistance of mosX board causes lower temperature rise of LED die and output declines slower compared to LED on Cu XP MCPCB. At 2.8Amps LED on mosX has ~15% higher light output compared to LED on Cu MCPCB.

2.8Amps is close to max. safe current for SFH 4715AS, both LEDs survived, but long-term LED reliability is not known.

What's interesting is that performance difference between two boards is quite visible for LED that has very large thermal resistance of 9 C/W, both boards have fraction of that, but when LED die reaches high temperature, it seems every additional C has significant negative impact on light output.

____________________________________________________________________________________________________________________________________________________________________________

Edit: 11.06.2018. Luxeon IR vs OSRAM SFH4715AS test

 

I finally tested Luxeon IR LED, specifically L1I0-0850090000000. Specifications look very similar to SFH4715AS, same typ. output, footprint is completely the same, biggest difference is much lower thermal resistance - 2.5K/W, OSRAM SFH4715AS has 9K/W. This should mean slower output decline at higher power due to lower chip temperature increase.

LUXEON IR is available with three different lenses, 60,90 and 150 degrees. 150deg version could be useful for reflector an TIR applications, while 60 and 90deg are more useful for lens lights.

I tested 90deg, because 4715AS is also 90 deg, but lens on Luxeon IR is quite bigger, and radiation patterns are not the same, so I used correction factor to match relative output (assumption is that radiation outputs are the same, as datasheets say).

Here are test results for OSRAM SFH4715AS vs. LUXEON IR on mosX (lux numbers for Luxeon IR are scaled to match OSRAM at low currents, where difference in thermal resistance has negligible effect on output):

I tested OSRAM up to 4,0A this time, so both LEDs can handle impressive amount of current without failure. Also after 4,0A test, I checked lux numbers at lower currents again, to see if there is damage due to high current, and both LEDs had same lux numbers as before 4,0Amps, so there is no short term damage from high current,at least not on mosX board.

Form test results it's visible that up to ~1.4A there is little difference in light output, but after that much lower thermal resistance of Luxeon IR board causes lower temperature rise of LED die and output declines slower compared to SFH4175AS.

This test confirm that 2.8Amps is close to max. safe current for SFH 4715AS, over that there is almost no gain, and output even starts to decline over 3,20Amp.

Luxeon IR has higher relative output over 1,40Amps, difference is about ~7% at 2,80Amps, and ~11% at 3,40Amps. Also Luxeon IR has considerably lower forward voltage over 2,0Amps.

Edited by: led4power on 06/11/2018 - 06:47
ggf31416
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IMHO this should be stickied. There has been several threads about IR and information was somewhat lacking.

Would you consider selling IR leds on your store already mounted on your boards? That would attract people who don’t want the extra work and risk of doing the reflowing themselves.

djozz
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Nice results. You get away pretty ok with a cheap non-DTP board but the Mosled Extreme board helps the output and probably also the lifetime of the led.

link to djozz tests 

“I used to think that top environmental problems were biodiversity loss, ecosystem collapse and climate change. I thought that thirty years of good science could address these problems. I was wrong. The top environmental problems are selfishness, greed and apathy, and to deal with these we need a cultural and spiritual transformation. And we scientists don’t know how to do that.”   (Gus Speth)

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Thanks for the testing led4power. Not knowing anything about IR Lights would this work well for a night vision scope?

My current and or voltage measurements are only relevent to anything that I measure.

Budget light hobby proudly sponsored by my Mastercard and unknowingly paid for by a hard working wife. 

djozz said "it came with chinese lettering that is chinese to me".

old4570 said "I'm not an expert , so don't suffer from any such technical restrictions".

Old-Lumens. Highly admired and cherished member of Budget Light Forum. 11.5.2011 - 20.12.16. RIP.

 

led4power
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ggf31416 wrote:
IMHO this should be stickied. There has been several threads about IR and information was somewhat lacking. Would you consider selling IR leds on your store already mounted on your boards? That would attract people who don't want the extra work and risk of doing the reflowing themselves.

I wiill consider this (I have several LEDs available now).

There is one interesting IR LED from Lumileds which is almost a copy of SFH 4715AS: https://www.lumileds.com/uploads/685/DS191-pdf

but it has much lower thermal resistance, 2.5K/W vs. 9K/W, I will test that LED to when I find some time.

BTW, in that datasheet there is one interesting graph, which shows light output vs. temperature:

This graph shows IR LEDs output drops much more with temperature compared to white LEDs, around 0.5% per degree Celsius, white LEDs output drops 0.2~0.25% per C at >100C die temperature.

This explains why output gain with mosX is higher than what I initially expected (when LED has high thermal resistance such as 4715AS - 9K/W, board resistance in theory has less influence, because no matter how good board is, total resistance can't be lower than 9K/W).

In my test light output at 2.8Amp is 15% higher with mosX PCB compared to copper XP PCB, this means die temperature is about 30C colder with mosX PCB.

 

led4power
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MRsDNF wrote:
Thanks for the testing led4power. Not knowing anything about IR Lights would this work well for a night vision scope?

They are often used in IR illuminators for hunting, and for home surveillance systems.

djozz
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I have that Luxeon IR at home for months now, as well as the tiny L1IZ-0850000000000 version, but did not find the motivation for a test yet comparing it to the Osram IR leds. I would not mind if that task is taken out of my hands Innocent

Btw, annoyingly the 3535-size Luxeon IR led does not have an electrically neutral thermal pad, it is connected to the anode Tired

link to djozz tests 

“I used to think that top environmental problems were biodiversity loss, ecosystem collapse and climate change. I thought that thirty years of good science could address these problems. I was wrong. The top environmental problems are selfishness, greed and apathy, and to deal with these we need a cultural and spiritual transformation. And we scientists don’t know how to do that.”   (Gus Speth)

led4power
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Updated OP with Luxeon IR vs OSRAM SFH4715AS test.

djozz
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Thanks for the new test! This Luxeon led will not shake the earth, but is does perform a bit better than the Osram led and the 0.16V lower voltage at 3A keeps it in regulation a bit longer on a 8×7135 lineair driver.

link to djozz tests 

“I used to think that top environmental problems were biodiversity loss, ecosystem collapse and climate change. I thought that thirty years of good science could address these problems. I was wrong. The top environmental problems are selfishness, greed and apathy, and to deal with these we need a cultural and spiritual transformation. And we scientists don’t know how to do that.”   (Gus Speth)