Broke the "3rd" Bond Wire on XP-G2 "de-dome", Still Illuminates the Same, Though.

matt304

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Broke the "3rd" Bond Wire on XP-G2 "de-dome", Still Illuminates the Same, Though.

I'm a little confused here. I have the weirdest luck with de-doming. Some XP-G/G2s, the lens peels off just fine with an exacto razor knife. Others, I get broken bond wires. I'm still learning I guess you could say. The XP-Es, those are hard for me to get one correct yet. I always take the razor, and peel up and back, from the exact opposite side of the two main bond wires. So I'm pivoting the lens more on the wires than putting the razor near them.

Anyways, here's one that gave me a question to ponder. What is the duty of the "3rd" bond wire, the one that does not travel to the chip-die, but across the bridge on the side of the Cree XP-G2 die? That is the bond wire that broke on a de-dome, and when I powered the light back up, it appears to have the same output power, still.

What is this extra bond wire, and what is its duty? Will I harm the LED by operating it without this extra wire?

Lastly, how do you de-dome? Someone said gasoline. I don't like that idea, it sounds dangerous to saturate a porous chip structure with an oily solvent. But the razor blade method seems to work about 50% of the time, telling me, "hey, you need a better idea".

There's obviously the lens, the silicone filler, and then a solid glue ring base of the lens on-chip. If the glue is touching a bond wire, that seems where it basically fails. So technically, I do need to soften that glue, I just don't know if there is someone's hidden quick trick to de-doming around here.

Thanks for the help.
 

alpg88

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Re: Broke the "3rd" Bond Wire on XP-G2 "de-dome", Still Illuminates the Same, Though.

Someone said gasoline. I don't like that idea, it sounds dangerous to saturate a porous chip structure with an oily solvent.
Thanks for the help.

it may sound dangerous, but many did that and it works out just fine. it is proven to work.

but if you still insist, take a thin sheet of plastic, or anything else, drill a hole same diameter as the dome in the bottom (the widest part) put the sheet over the dome, and cut off what is sticking out with a razor, but make sure you slice it, not just push the blade into it. thickness of the sheet is the hight of silicone you will have left on the led. you will have to practce so the cut is smooth, it took me 3-4 leds. you want sharp blabe and do it in one slice.
 

RoGuE_StreaK

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Re: Broke the "3rd" Bond Wire on XP-G2 "de-dome", Still Illuminates the Same, Though.

What is this extra bond wire, and what is its duty? Will I harm the LED by operating it without this extra wire?
That's the ESD diode. It'll work without it, but you won't have ESD protection

how do you de-dome? Someone said gasoline.
91 octane petrol. 100% success rate (of one XM-L de-dome)

I do need to soften that glue, I just don't know if there is someone's hidden quick trick to de-doming around here.
Some apply current without a heatsink for a few seconds, supposedly the dome pops right off leaving a silicone layer.
 

matt304

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Re: Broke the "3rd" Bond Wire on XP-G2 "de-dome", Still Illuminates the Same, Though.

Thanks for the help guys. I like the idea of using both methods... That is, soak in gas, dry quickly, heat, and pull. That sounds like a good combination trick. Thanks

I dismiss the plastic sheet idea not because it sounds like a bad idea, but only because for me, I would rather have a more, "complete" removal, if you will. If I arc the blade at all, or say it exceeds the glue strength, I could still end up moving the dome very slightly, I would imagine. Still possibly pulling a wire. You may say no way, as you may have it figured out, but I think first for me, I will try attempts at a glue-softening removal technique. Though, I do give credit to your method of the plastic sheet, as it would probably leave the bond wires quite intact and protected after the center of the lens is gone and a ring of lens is leftover. Might have to experiment with all 3 methods in the end. But we all know, heat likes to soften polymers.
 

LEDealer

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Jun 23, 2013
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Re: Broke the "3rd" Bond Wire on XP-G2 "de-dome", Still Illuminates the Same, Though.

At the risk of sounding like a LumiLEDs fanboy (which I'm not), why don't you gentlemen and ladies just use something like a LUXEON Z ES?

Is it because you're trying to retrofit something and the pad layout is different?
 
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