What to do with "broken" Cree Q5

[wildstar87]

So I got impatient and tried to solder one of the Q5s I got with a soldering iron tip that was too big. Long story short, I heated up the metal ring on the dome, causing the ring/dome to pull away from the board.

The LED still works, even though the ring/dome is separate from the board now.

I was wondering if anyone had any suggestions what I could do with this now... :sigh:

I don't suppose anyone knows how I could get the ring/dome back onto the board and if it would even be worth it at this point. It is interesting to see how much the dome MAGNIFIES the die. When I look at it on the board, it's TINY.

 

[DonShock]

I was building a multiple LED light and had a dome pop off. I didn't notice until it was finished and one LED was significantly dimmer than the others. I found the dome rattling around in the light head when I disassembled it to investigate. I had planned to just write off that one LED for the time being and replace it at a later date. But I decided to epoxy the dome back in place to protect against further damage. I was very surprised to find that just epoxying the dome back in place restorred the LED back to full brightness.

I used clear 5 minute set epoxy. I spread a very thin layer on a paper plate and then dipped the bottom of the dome in it to avoid glopping on too much epoxy. I don't know if it will work in your situation, but it might be worth a try.

 

[SteveDavis]

Apart from the obvious loss in brightness from re-epoxying the glass lens (which may or may not be noticeable) you also may have lower lifetimes when experiencing variations in temperature. You'll notice when a lens pops off that the encapsulant is much softer than even the softest silicone lenses on the market. This is so that the glass lens can float up and down as the package heats and cools, putting less stress on the emitter and the wire bond. Using a hard epoxy will limit the ability for the lens to float, so it could impact lifetime.

Other than that, if it works for you, go for it.

 

[Gryloc]

Be careful about having the cheap 5 minute epoxy from getting too close to the die, even if there is a little bit of original soft silicone surrounding the die. I used the typical 5 minute two part clear epoxy that I got from my local WalFart store, and the heat from the LED caused the clear epoxy to discolor. At first, things were clear during operation. It took less than 15 minutes of operation before a light brown spot formed over the LED die. After 30 minutes of operation, the brown spot got much darker. I feel that it may have hurt output a bit, and it put some warm, brown colored artifacts in the flashlight beam. I believe that the soft silicone around the die also acts as a medium to conduct heat away from the die. You may be hurting the heat transfer by using a hard epoxy. Has anyone ever tried the clear silicone adhesive paste that comes in a tube or a caulk tube? I wonder if this would act more like the original silicone material.

Of course, I used a small glob of the epoxy over the die (encased in a little soft silicone) and used the emitter after that. I didn't really put on the original dome.

Also note that the beam pattern may change. I am not sure how the change of mediums effect the refraction of the light. You could end up with a larger beam spot, a smaller beam spot, or maybe a beam with ugly artifacts.

I guess that you have to be careful and give it a shot. It wouldn't hurt to replace it down the road and toss this one in a less important torch. Luckily Q5s are getting cheaper and easier to acquire. Good luck!

-Tony

 

[LED Zeppelin]

I tried to re-silicone a dome back on, but couldn't get good adhesion with the particular silicone I was using, GE Kitchen & Bath. I weighted the dome while it cured, but with unweighting air pockets appeared. It very well could be bad silicone because I have since found that it is not curing properly. I'm sure the optical properties leave much to be desired anyway.

I'd recommend using the LED for something other than a flashlight you care about. It would be suitable for a fixed lighting project. I've unpackaged several new emitters that have air pockets under the dome. I'm saving those for such a use.

 

[richdsu]

Read here :-----

http://www.candlepowerforums.com/vb/showthread.php?t=175648