"Crack" behind 5W die, should I be worried?

\"Crack\" behind 5W die, should I be worried?

Ok, I got a colored (not white) 5W emiter. I haven't installed it yet. Just for grins I pulled out my 30x pocket microscope and was looking at it it. Then I noticed behind the grill looking LED dies, in the shiny part behind them there was a dark squigly line. It goes behind 2 of the dies (half of the emiter).

I can't tell if it's a crack or a microscopic hair...
Anyone seen one of these before.. I sure hope it doesn't fail after I mod it. With all the money & trouble I went through for this I will be extremely mad!!

Is it a go or no-go? Or a We don't know?
Any case I guess I will find out. What are everyone's experiences? I sure hope someone doesn't say "yep it's a dud" /ubbthreads/images/graemlins/icon15.gif /ubbthreads/images/graemlins/banghead.gif /ubbthreads/images/graemlins/mecry.gif

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That's normal.

Look:
http://myweb.cableone.net/evan9162/5wrb.jpg
http://myweb.cableone.net/evan9162/1wdie.jpg

A luxeon die makes electrical contact through tiny solder blobs on the bottom of the die. THis is similar to the BGA (ball grid array) packaging that components are attached to PCBs with nowdays. This is where they get the "flip-chip" name for luxeon LEDs.

On the silicon substrate (which is epoxied to the heat sink slug), there are contact patches. The die is electrically (and thermally) bonded to these contact patches through the solder blobs. The bond wires also are spot-welded to these contact patches. The "crack" you see is merely a break in the contact patch to electrically isolate them from each other.

There are 2 of these on a 5W, since it is a series-parallel configuration of dies. The outer contact patches are connected to the bond wires. The single inner contact patch serves to electrically bridge the anode and cathode of the dies together to complete the circuit.

These breaks in the contact patches are harder to see on the 5W white, since the phosphor covers up evidence of their existence. The color 5Ws more readily show their prescence.

A single break also exists on the 1W, but is harder to see since it is close to the edge of the hexagonal substrate the die sits on, and the 1W is just physically smaller than the 5W.

So it's normal, nothing to worry about.

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Hmm. I don't see them in your photos. I'm attaching a picture I made real quick to describe more accuralty where the "crack" is seen on mine. Let me know if this is what you are talking about...

\"Crack\" behind 5W die, should I be worried?

Only if a cop stops you /ubbthreads/images/graemlins/smile.gif

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hehehe. Well, if it works, then I don't think he'll be able to see it, or anything for that matter for a good while /ubbthreads/images/graemlins/grin.gif
I'm more worried once I get this built, that cops will come after me for disturbing the peace!!

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Bump. Oh yeah, I'm making that picture into a full blow emitter. I might make it shinning or something too. Photoshop is fun. I wish I had more time to get back to my huge files and projects. Can't wait until schools out..

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Issac,

I hope you don't mind, but I modified your picture to represent where the "appropriate" cracks are for a 5W.



From this, you should be able to see the corresponding lines in my 5W picture. The appropriate line in a 1W appears (relative to the die) in the same place as the top line I've drawn on your 5W graphic.

The crack you've drawn definitely looks like something else. If it is a crack in the die, I'd still say everything should light up properly, since the bottom of the die is covered in solder bumps, so there aren't any parts of the die not receiving electrical contact due to the crack (that's the way it appears to me, at least).

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Hmm. As long as it works fine, I don't care!
I'll find out soon. Then when I mod it I'll find out if it will affect it in the long term /ubbthreads/images/graemlins/icon15.gif

BTW do you like my picture? I think it came out close to how they look.. /ubbthreads/images/graemlins/grin.gif

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Very nice graphic. Compare it to the image on Craig's (Led Museum) page about luxeons.

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I actually made it in refernce to your picture of the 5w RB SE die. They look differnt colors in different photos but they all look like a mirror surface to my nake eye.
Craigs photo shows one die that has that dark squigly like line thing mine has. Maybe it's just discolorations..

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It powers up just fine. Haven't ran it yet as I don't have it installed or enough power for it. Hopefully it won't exploded after it warms etc... I don't think so, I think it's just a discoloration for some reason. I belive I can see it in other macro photos...