A Perfect Dedome?

coleman fuel?

Oh Oh, it was me who suggested Coleman I'm afraid . Can you make a macropicture of the led?

I am beginning to love pictures of damaged leds, here is one of a damaged, but working xpg2 :

The XRE that I de-domed was actually an XLAMP-7090, the first gen XRE. The led die is covered by the dome material and then a hard plastic lens. It looks like the phosphor is mixed in with the dome material and not a separate layer on top of the die. Remove the dome and you remove the phosphor…

I just reflowed a XPG2 die back onto the substrate(!), and the damn thing works. It got overheated during the first reflow and the middle of the die looked burnt out so I tossed it in the gasoline just for entertainment, found the die no longer attached which is why it acted just like one that's running too hot. Put a tiny tiny tiny little dot of solder paste on the substrate, carefully folded the die back down, and hit it with hot air from the butane torch. And the damn thing works now!

You should ask Cree to hire you, you would lower them the rejects rate :D

P.S. I dunked one XP-G R5 into medical gasoline for about 3 hours but I must have damaged the wires when removing the dome. Damn thing is sooo small, need a microscope to see what am I doing...

I use a 10x lighted loop - it's not too bad with one hand holding the loop, and the other doing the tweezers. Got the loop from FT - they call it 30x but it's really about 10x and 2 LED's in it throws a lot of light. You have to have both - magnification and light, at least for me...

Ill take a led that sits on a mcpcb, put it in a little glass jar with petrol, and a lid. Let it stay there for 4+ hours.
Usually, the dome have fallen of, if not I just “shake” the glass a little bit carefully sideways. When the MCPCB hits the glass, the dome will fall off if its not already off.
So far, I never had to even touch the dome. I always make sure the led/dome points upwards…

I thought to get one of those USB "microscope" cameras! it's easier to work when you have 2 hands at disposal :)

For me in the gas, the dome is always off or lifted, so not a problem with the dome. What I do is remove as much silicone material around the emitter as possible with tweezers without touching or getting close to the wires, but the emitter phosphor surface itself always comes out clean. I'll squirt iso. alcohol all over it before the work and after when all done.

Thanks for all the tips guys. I’m now an official member off the dedoming club after successfully using the petrol (gasolene) method on a poor little XP-G2. Theres a big brother XM-L in the tub as we speak.

Congratulations MRsDNF! It is good fun to find out what dedomed leds can do !

Apart from being a flashlight snob I used to collect microscopes, so I use one of these to see what I am doing when dedoming:

(the famous Olympus SZIII zoom stereo microscope, introduced in the sixties, still widely used)

Thanks djozz. I put the XM-L in a P60 today and what a dismal failure. There was shadows everywhere. having a look under the magnifying glass there was a couple of remnants of the dome left which were dispatched with. Back in the light there was not a lot off difference. I machined the edge of the pill down to try and tune the reflector better but l could not get a nice beam at all with it. Drilling the hole out for the led also made little difference. Another type off reflector was tried to no avail. I cant see any remnants of the dome left but there must be. I will have to try it in a bigger reflector when the motivation returns.

If you didn't already, try it with the thinnest possible insulator, or none at all if you can do so without shorting anything. They really have to be poked way up in there to throw a halfway decently tight spot.

A dedomed led is focussed best when it sits just a bit deeper behind the reflector than when the dome is still on, because a dome (=positive lens) makes a virtual image of the die that is sitting 'deeper'. I don't know how to explain it better, sorry.

Perhaps that is what is happening here?

Another trick to get it focused, since on a conventional MCPCB you can't raise the LED any higher than just where it goes, is to machine off some of the flat base of the reflector, the part that normally contacts the centering ring. That has almost the same effect as raising the LED (but not quite, as there's still no reflector surface 'behind' the LED). Also has the effect of enlarging the hole, due to the internal shape of the reflector surface. If you just bore that hole larger it's 'bout guaranteed to make the beam worse. (been there done that, way too many times)

Thing is that compared to a domed led, a dedomed led should sit not deeper inside the reflector but rather more backwards, so you need not machining the reflector down but use an extra spacer.

I have found the exact opposite. But there are many different variations in p60 reflectors - some have a rather wide flat area/'shelf' around the emitter hole, some a narrow shelf, some a smooth taper all the way to the bottom. Who knows how many are properly designed and how many are just poor copies of copies of another design...

Thanks for the advice guys but believe it or not I tried all the above, hence the lack off motivation right at this point in time. The lathe does come in handy for machining pills and the back off reflectors. Its got shadows in the hot spot which makes me think that it must still have part off the dome on the emitter that I cant see. I’ve added some nightshots of the XP-G2 here at the end off the first post which I’m really happy with.

Oh boy, the smallest light I used a de-domed emitter in was a C8, but got about 100 kcd with it, so doubled the kcd - it's a XM-L2 U2/SinkPAD running at 3.85A I believe. I haven't noticed any issues like that in the beams of all the de-domed lights I did, quite a few now. My biggest is my TN31 which is doing 347 kcd - pretty sick for under $10 in parts, posting in this thread: https://budgetlightforum.com/t/-/17637.

I'm thinking the XM-L2's de-dome easier/better - pretty much all my de-domes, accept the very first, are XM-L2's.

And all of my dedomes thusfar (exept for 1 test) are xpg2's and xpe2's I did them all hot, without the gasoline by the way.