Deceased Cree Emitter or not?

[wes_wall]

Ok, I am a newbie, but not a complete buffoon.

I read and followed advice on removing an emitter from a star and got a little clever; or so I thought...

I set up a redneck hot air reflow soldering station by mounting my heat gun pointing up. I tested it with my thermocouple hooked up to my multimeter and was satisfied that it didn't get too hot too fast. I then gripped the cree LED carefully by the little square PCB with a very large hemostat. I was careful not to apply crushing pressure. I held this thing attached to the star over the hot air flow heating only the star from underneath. The star fell free of the emitter after about 1 minute. It was delightful!

The emitter has been sitting here on my desk happily for a few days. Several times I picked it up always by the PCB to study it. Never anything more than holding it in my fingers until today.

I went to move it because I was rearranging something and the dome just snapped off. A better description is it slipped off.

Are these things really that delicate? I read about the potential for potting these things on one of the threads. I am thinking that may be necessary for a high stress use as in dive light and bike light.

Am I right? Do I possess superhuman strength? No one is responsible for destroying it except me or does it sound unreasonably delicate to you guys? Of course no one can tell what I did to destroy it, but do they require this extreme handling or does it sound like I had a defective one?

What if I bounce the dive light on the deck of a boat? while underwater? in the dark? Can it be repaired with the super-duper water clear epoxy or is this one fro the 'gee whiz' file?

 

[Myself]

Well, I just killed an XR-E because I was a moron. A pair of them, actually. I forgot about the "don't push the dome" stuff, and just clamped onto them to press their star modules down into the thermal glue. Everything looked fine at first, but ten minutes later when I removed one of the clamps I got a nasty surprise:

Needless to say, that's not what I intended! Oh well, good thing I have spares. More photos of the build (and its immediate predecessor, which is already completed) in my flickr: http://www.flickr.com/photos/myself248/

 

[Greg G]

Just get a new one. Yep, the domes are easy to remove. Best not to ever touch them. Pretend they're poison.


Also, just my opinion, but applying heat to an mcpb for an entire minute to get the emitter off is too long. increase the heat, shorten the duration.

 

[Greg G]

That'll teach you. :sick2:

 

[csshih]

Well, I just killed an XR-E because I was a moron. A pair of them, actually. I forgot about the "don't push the dome" stuff, and just clamped onto them to press their star modules down into the thermal glue. Everything looked fine at first, but ten minutes later when I removed one of the clamps I got a nasty surprise:
Needless to say, that's not what I intended! Oh well, good thing I have spares. More photos of the build (and its immediate predecessor, which is already completed) in my flickr: http://www.flickr.com/photos/myself248/

ouch... did the xr-e still work afterwards? just wondering :candle:

 

[saabluster]

Ok, I am a newbie, but not a complete buffoon.

I read and followed advice on removing an emitter from a star and got a little clever; or so I thought...

I set up a redneck hot air reflow soldering station by mounting my heat gun pointing up. I tested it with my thermocouple hooked up to my multimeter and was satisfied that it didn't get too hot too fast. I then gripped the cree LED carefully by the little square PCB with a very large hemostat. I was careful not to apply crushing pressure. I held this thing attached to the star over the hot air flow heating only the star from underneath. The star fell free of the emitter after about 1 minute. It was delightful!

The emitter has been sitting here on my desk happily for a few days. Several times I picked it up always by the PCB to study it. Never anything more than holding it in my fingers until today.

I went to move it because I was rearranging something and the dome just snapped off. A better description is it slipped off.

Are these things really that delicate? I read about the potential for potting these things on one of the threads. I am thinking that may be necessary for a high stress use as in dive light and bike light.

Am I right? Do I possess superhuman strength? No one is responsible for destroying it except me or does it sound unreasonably delicate to you guys? Of course no one can tell what I did to destroy it, but do they require this extreme handling or does it sound like I had a defective one?

They are delicate but not that delicate. You do actually have to push on the dome to get it to come off. If it just fell off without you having touched it than that means you probably damaged it when you were removing it from the star. Even though you may have had the temperature right if the gel had moisture in it when heated it can expand and can cause the dome to become loose. Cree recommends that the LEDs be baked for several hours(more info in their data sheets) to get rid of the moisture before reflowing. I'm not saying that was definitely it but its probably the most likely if you are positive nobody messed with it. As long as all the precautions are taken when soldering them there is no need to worry about the lens popping off even if you drop your light.

 

[Myself]

ouch... did the xr-e still work afterwards? just wondering :candle:

Yup, both of 'em light up just fine. I might repurpose one as a flood or nightlight, since only the optics mounting seems to be damaged.

Actually I bet the radiation pattern isn't even that screwed up, since only some of the goo got out. I might just throw one of these suckers in a light and see what happens.

Hey, speaking of bake-moisture-out requirements... presumably the same damage could happen if the emitter were inadequately heatsunk and the poor thing got itself up to 100C, right?

 

[tx101]

Reading this post has me really concerned
I need to remove the stars from 5 Cree R2s
I was just going to hold them upside down and heat up
the back of the star and just let the emitter drop off

Now I am scared of damaging my emitters

 

[olrac]

+1 to what saabluster said. very likely you steamed off the dome. With Cree emitters I bake them in the oven at about 200 degrees F for about 4 hours when in doubt about moisture content and then promptly remove them from the star and reinstall right away. If you don't reinstall right away the emitter can pick up moisture from the surrounding air and you can wind up with the same problem and have to bake a second time. I have never had a dome come up doing it this way.

 

[wes_wall]

Yes, she will light up! All I can see just now is a big green blob floating around in front of me!

Thanks for the quick response. I am glad to know about the preheating thing. I did not do that. That piece of knowledge cost me $5. A cheap lesson really when you think about it.

 

[Myself]

It's always a good idea to read the datasheet for each part you're using, even if nothing seems immediately relevant, you'll learn little details that will inform your future work. Start here:

http://www.cree.com/products/pdf/XLamp7090XR-E.pdf

Curiously enough, the datasheet doesn't mention "don't push on the lens!". I know I've read that somewhere. Oh well! Mine was a $10 mistake because I don't build a lot of single-emitter lights. Could've been $15, if the body on this one was larger!

Edit: Soldering and handling is here: http://www.cree.com/products/pdf/XLampSolderingandHandling.pdf

The Cree.com product page is a good place to start...

 

[collector]

In some really heavy duty lights I had built, I had this happen twice to me already. If you have a light where the reflector sits on or around the metal ring of the Cree, and with nothing else holding the driver-board on the top side, it is bound to happen. The light itself is durable as H*LL, the these lights were used to getting banged around, I also showed of by hitting it agains a wall or trowing it across a parking-lot and such.

The funny thing is, they do keep on working, even if the dome snaps. I removed it from the dome from the head and replaced the lens. At medium (indoor) ranges, with sanded McR reflectors, the beam is TIGHT ! However, with no lens, it's a different focus all together, so for longer ranges, it's off... The other difference is that the tint also shifts toward the LuxI type of cat-pee yellow-green... I had the same happen in both cases...

My $0.02...

Cheers !!