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How can I salvage LEDs that are welded to metal heat sink? Answered

I have a light fixture that used to be an street lamp, and the 350mA 240V constant current ballast failed. The LEDs appear to be welded directly to thin insulated metal sheets which as somehow bonded to the large metal heatsinks. I think the LEDs are Cree XR-C's, and there are 6 of them on each module, and there are I think 6 modules in total.

I have some ideas, but how would I get the LEDs off the modules, if they are even worth saving at all? They are according to CREE they produce 78lm @ 2W, and are a pathetic 39 lm/watt. If I can get them off the aluminum heatsink easily enough, I might be able to use them for prototyping purposes so I do not kill $$$ XM-L LEDs, and do not kill 3mm white LEDs either, since I tend to kill those quite fast too by overdriving them or too much voltage.

It is amazing to think how far technology has come, that XML led sitting next to the module outputs more than double the light, with less 20% less power!!! I have always thought that LED technology still has a WAY to go before becoming practical enough to justify the higher costs, but if a company has installed this Piece of Sh*t light fixture back when these LEDs were 'state of the art' than I wonder when metal halides go obsolete!

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Vyger

Best Answer 4 years ago

There is a thermal epoxy I used to use for mounting little heatsinks on individual chips. It is both an epoxy glue and a thermal compound. I would not be surprised if they used the same kind of thing on this. So removing them without damage might not be possible. I have to wonder though, that is quite a heat sink, do they get that hot?

I would think about cutting the heatsink into sections with the individual LED's still mounted to them. It would be easy to solder some leads onto the contacts. And that way you have a built in heat sink for each one. Aluminum cuts pretty easy so even a hand saw should have no trouble getting them apart.

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-max-Vyger

Answer 4 years ago

I think what I will plan to do is make a lamp above my workbench that will illuminate everything. I will need to develop another constant current source that can deliver 100W. I might use a ZVS driver to generate the voltages and current. I find those are pretty reliable, efficient, and powerful!

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-max-Vyger

Answer 4 years ago

I am not sure, but considering that this draws 12W at full power, I'd imagine that heatsink is necessary since the majority of that power is being converted into heat and it is in an enclosed in a small fixture. There are 8 of these that make up what looks like an upside down octopus, and the heat I suppose rises creating a draft from the convection. There was no cooling fan, so it was a completely passive system.

Interestingly, there is a control board that turns the ballast on and off and it what appears to be a 900MHz antenna. There were apparently plans to make the light flash when 911 was dialed, acting as a beacon to emergency vehicles! It was never fully implemented though. I can see how that would take into advantage the benefit LED lighting has, and that was probably the selling feature, considering these LEDs would have been less than 40 lm/w when similar metal halide lighting is above 80 lm/w! (Of course not taking into account the optical design and deterioration and dirt buildup over time.)