Diode Degradation

I recently metered my A140 in my projector that was running at 1.8A. I have had it in the projector for about of year with medium use (for a projector). Over that year the diode has dropped almost 400mW in power.

I understand that diodes degrade naturally over time due to oxidization, temperature, light output and moisture.

Has anyone else had similar experiences with diodes degrading?

I also wondering just how much of diode degradation can be attributed to running the diodes at the high currents we run them at.

The A140 in my ancient but trusty Jarob 18650 kit was failing at about 400mW @ 1.7A ! , whacked in an M140 and it was doing 1555mW with 3 element lens an pushing 1900mW with the G-2 , from a single 18650 & flexdrive.

The A140 had been de canned a long time ago so I presume that sped up the degradation.

ARGLaser said:

I recently metered my A140 in my projector that was running at 1.8A. I have had it in the projector for about of year with medium use (for a projector). Over that year the diode has dropped almost 400mW in power.

I understand that diodes degrade naturally over time due to oxidization, temperature, light output and moisture.

Has anyone else had similar experiences with diodes degrading?

I also wondering just how much of diode degradation can be attributed to running the diodes at the high currents we run them at.

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There is also the problem of the beam damaging the diode window.
As the window burns, it blocks more of the light (and causes even more heating of the window)
A couple of members have actually had the beam burn through the window

ped said:

The A140 in my ancient but trusty Jarob 18650 kit was failing at about 400mW @ 1.7A ! , whacked in an M140 and it was doing 1555mW with 3 element lens an pushing 1900mW with the G-2 , from a single 18650 & flexdrive.

The A140 had been de canned a long time ago so I presume that sped up the degradation.

Click to expand...

De-canning itself should not be an issue.
The final coating of the die should stop any interaction with the environment
However, the exposure of the facet to the environment can lead to accumulated "crap" on the die face

Peace,
dave

Arglaser, I hope you don't mind me asking in your thread, I was wondering recently how much of a factor humidity is in degradation of diodes. For a while I had thought the lower the humidity the better and have my lasers stored in a container with jars full of rice to absorb moisture. However recently, (can't quite remember where) I remember seeing on a diode spec sheet or laser spec sheet a suggestion to maintain a minimum humidity above a certain amount. :thinking:

ElectroMagneticFreak said:

Arglaser, I hope you don't mind me asking in your thread, I was wondering recently how much of a factor humidity is in degradation of diodes. For a while I had thought the lower the humidity the better and have my lasers stored in a container with jars full of rice to absorb moisture. However recently, (can't quite remember where) I remember seeing on a diode spec sheet or laser spec sheet a suggestion to maintain a minimum humidity above a certain amount. :thinking:

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That's relevant to this thread, I always though the less humidity the better too. I store my diodes and lasers with silica gel as well, to keep out the moisture.
Could the lack of humidity contribute to diode degradation as well? :thinking:

You did use a C-WIND (chip-weevil instant negation device) in your projector, right? If not, you might need to clean the CW droppings from the lens

I used a new lens to test the power, so it would only be dust accumulation on the diode window and within the diode to effect the power.

1.8A is a good bit above what I was running A140s at when I was using them in my projectors, and mine lasted over a year with lots of weekend usage. In fact, one of them is still going strong at 1A to this day. My first guess as to the reason for degradation would be too much current, which you touched on in the OP..

How much of the degradation can be attributed to the high currents though? Would this have happened running the diode at .8A? I am trying to figure out what it is that makes these diodes degrade the most, and if it can be stopped.

No. 1 cause of degradation is too much current or transient voltages. Can these be prevented? Yes, but only by running at lower current and eliminating the possibility of transient voltages. Most quality drivers make transient voltage damage nearly (but not entirely) impossible, but with overcurrent it's up to you to set the current at a safe level. Compared to running an A140 diode at 1.8A, .8A would give a far longer life. .8A is probably lower than really necessary. I would say 1.2A on the high side for A140s for a nice long life.

The way diodes react to overcurrent isn't always linear, ie the higher current doesn't always give proportionally shorter life, the life could be WAY shorter for one diode or not much shorter at all for another. Since no two diodes are identical, neither is the way they respond to abuse. When manufacturers rate diodes, they conservatively rate based on a time period that ALL tested diodes prove they are able to reach. Because of this, we as hobbyists often have a little leeway in terms of how we run our diodes, but past the ratings there are no guarantees.

Since I was a bit vague, when I said before that my A140 diodes lasted over a year in projectors, I meant that they lasted until I upgraded. The diodes are still perfectly good, making full power. No measured degradation from new as of the time that I pulled them.

Thanks! That's exactly what I wanted to know.

Would it also be possible that running the diode over the rated current would burn up the diode window faster than normally as it's producing more light than it's meant to?

Quite possible, however it's my opinion that the burned windows you've seen and heard about were caused by dirt on the glass. It doesn't seem to me that it has happened often enough to be a common trait of 1W+ blue diodes with windows. Dirt can cause problems because depending on the composition of the particle or smudge it will be heated by the energy it's exposed to. When that happens it becomes hotter than the glass, which is coated so that heating is minimized. With such high power levels it's possible that the material can become hot enough to burn the anti-reflective coating and eventually melt the glass itself or cause the beam to melt the glass. This is just my theory though, so it's not proven and could be wrong, but it seems sensible to me..

Re: humidity, you minimize the likelihood of ESD at about 50% humidity. The cleanrooms where semiconductor wafers are made are typically held at 50% humidity for this reason. The environment is going to be oxidizing no matter what you do, so you mitigate that in other ways and control humidity to at least try to prevent ESD.

ESD is a huge deal in manufacturing. Cleanroom suits are actually slightly conductive and grounded to the conductive floor for this reason. Everything is grounded, even rolling chairs. Lots and lots of steps to reduce the chances of ESD.

Yeah, yeah, they get all the good toys, and all the fancy safety equipment to go with it. What we all want to know is, what does PBD's workshop look like? :wave:

I am curious what the biggest factor that causes long term power degradation is, that we may focus our efforts on the big elephant in the room, rather than the marmoset in the corner.

BShanahan14rulz said:

Yeah, yeah, they get all the good toys, and all the fancy safety equipment to go with it. What we all want to know is, what does PBD's workshop look like? :wave:

I am curious what the biggest factor that causes long term power degradation is, that we may focus our efforts on the big elephant in the room, rather than the marmoset in the corner.

Click to expand...

This reminds me of when the Chimp used to show his workshop and those completed 20,000.00 builds.:cryyy: