Peter has adressed Lumileds about the "farkle" problem.
From the same thread where the pic came from:
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Gransee said:
Klaus- I hope you don't mind me using your picture. I hosted this copy so it doesn't use your bandwidth.
I too was very concerned for the health of the LED when I first noticed the farkle. My thinking was that the silicone was obviously placed there for a reason and moving it might affect the delicate parts inside.
I spoke to alway helpful Sal Cassirino at Lumileds about this and this is what I learned:
- The material is a silicone gel. It is two part and does cure from a liquid to a gel. It is placed inside the dome to facilitate optical coupling between the die and the dome lens.
- It is normal to find a small amount of residue on the outside of the black bezel. Pressing on the lens may cause a very small amount of oozing (Sal said he observed it with a microscope) but should not be appreciable.
-Pressing on the bezel certainly should not cause any silicone to ooz out of the dome. The bezel is designed for relatively large loads and transfers any pressure past the dome, die, cup and aluminum slug directly to the PCB.
Btw, All Arc LS designs do not apply any downward pressure to the dome of the LED. We press the NX05 optic firmly against the bezel only.
- If some how some of the silicone was removed from inside the dome, a bubble would result near the edge that would interefere with coupling in that area. It would not damage the die.
- Clean up of the residue is fairly difficult because of it's oily, sticky nature. Care must also be taken with the nearby dome. Lumileds is looking for solutions we might use to clean this area. We (Arc) have also come up with several methods that reduce (but not elimenate) the amount of residue.
See my notes above for other farkle thoughts.
Hope this helps.
Peter Gransee
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