Positioning of the Cree dome (lens).

After reading a few posts about Cree domes coming off, I managed to dig up 2 patents from Cree about the their Xlamp series LEDs:
7,279,346
7,326,583
Use http://patft.uspto.gov/ to search the above 2 patents.
Here's a picture from 1 of them:

Indeed, the only thing holding the dome in place is the encapsulating gel (18), so it's not difficult to knock it off if you're not careful . Another interesting observation (from the picture and my own inspection of an XR-E), is that the diameter of the dome is smaller than the internal diameter of the metal ring. This means that there is some play involved when positioning the dome during assembly. What will happen is that you may occasionally get a Cree that has the dome off-centered in relation to the LED die (the die itself is centered within the metal ring though). I've confirmed this visually with one of my Cree Q5, the dome was slightly off to one side.
I'm not sure how much this will affect the beam when used in a flashlight but I think it does play a role, especially when there is an off centered cree-ring/corona yet the LED appears perfectly centered within the reflector. What do you think?

Interesting, but how did you get pictures to show? I only get text.

Thanks for the patent search. That is good reading. I do not know if they still use the first quantity of encapsulant material #14 and then go back and put in #18 but they may. I have noticed that the #14 stuff sticking to the die seamed like it almost had a harder gel texture to it than the #18 stuff.

I have measured the tolerance of the dome fit and in my samples the part #5 ID is about .005" larger than the dome. So the farthest the lens could be offset is 0.0025".


Cheers
Dave

Also it is very curious that they do not want the lens to come in contact with surface #22, but to float above it.

Unfortunately I know how easy it is to knock the dome off the emitter . You only have to put a little bit pressure on the dome so you squeeze it into the gel and damage it. That's how I did it with one emitter. After this the dome fell off .

rayman

After they finish encap the lens, the leds will go for auto test. So output(leds) only for in spec range(bins). I was in the assembly line before.
Die it self have different output.

zzonbi said:

Interesting, but how did you get pictures to show? I only get text.

Click to expand...

see here ==>
http://www.uspto.gov/patft/help/images.htm

install the AlternaTIFF viewer


Cheers
Dave