Today was "Round 2" of the Osram Oslon 3rd Gen De-Doming trials.
It was a long day, full of fumes, danger, trial & error. Again, there were five lucky candidates, but unlike last time, all of them are still working after the de-dome.
I started the day by purchasing a spare fire extinguisher, as I had planned to add some heat into the equation today, along with some Prep-Sol, Thinners, & Petrol.
Here are the five candidates laid out prior to starting;
And here is the test setup I used. Hot air re-flow station, with tip removed;
I had no idea how it would perform, but at least it was adjustable, & there was no naked flame....
Test #1 was the Prep-Sol (Preparation Solvent), which is generally used to wipe down a surface directly before applying paint to it. The LED was not altered/cut, & was immersed into the hot liquid.
In it goes;
The setup worked very well - I was able to quickly bring it to the boil. There was also a little turbulence as a result of the boiling. I monitored it with an IR thermometer, & kept it around the 120 DegC mark.
I kept it in there for an hour, & periodically removed it to check progress. After ~15 mins, I noticed one side of the dome had separated. The dome appeared to open up gradually, like a clam-shell, but never fully separated. I had to top up the fluid several times, & ended up boiling off around 200ml.
I decided to put it aside, keeping it in the fluid, & move on to test #2.
Test #2; Enamel Paint Thinners.
This was probably the most likely to go up in flames...
The second unmodified LED was boiled for over three hours in the thinners, with periodic checks, & many top-ups. I went through about 700ml in this test.
Similar to #1, the dome separated early, but never came completely off. I was tempted to give it a prod, but I kept hearing "keep your mitts off of it" in the back of my mind....
After three hours, it was clear that it was not coming off by it's self. I could see that the dome had completely separated from the phosphor over the die & bond wires, but was still attached to one edge.
During this time, I decided to put LED #1 into the thinners as well, so it ended up being in for 1.5 hours.
Both LED's were in the same "Clam shell" state, so I carefully removed the dome off the last edge of them both;
LED #1 & dome;
Ignoring the left-over phosphor around the perimeter, it came out fairly well.
LED #2 & dome;
Not so good; a large patch of phosphor is stuck to the dome. This was not done by me removing the dome - it had already occurred during separation in the fluid.
Test #3; Petrol.
The unmodified LED was submersed in the boiling petrol, & after ~5mins, the dome was starting to lift at the edge.
It was in for a total of only 14mins until the "Clam" had opened, again leaving the dome attached at just one edge.
Here's how it looked;
Again, some phosphor has stuck to the dome during the separation process in the petrol.
Test #4; Powered LED in room temperature petrol.
This is the method that I hinted at in a previous post; Applying power to the LED whilst submersed in petrol.
Here's the setup prior to adding the petrol;
Cell used is a Samsung ICR 28A @ 4.0v.
The plan was to observe it using the auto-darkening welding mask.
This was a little intimidating - I really didn't know what to expect when I hit the power button....
The LED lit up, & within a few seconds, there were bubbles coming from the dome. I cycled it a few times, & checked it, but there was no apparent change yet.
When I was pretty sure it was not going to explode, I grabbed a photo through the welding mask;
After that, I let it run for a while, when all of a sudden it let out a 'pop'! I had my finger on the button, so let it off immediately.
I regained a little composure, & inspected the LED - there was a black bubble in the center, but it did not look like the dome had been breached.
The LED still worked, but I figured it was toast, so I put it back in, & this time hooked up a 25R to it. It bubbled away again, a little more vigorously this time. I realized that with the low voltage of these LED's, I had applied too much power initially.
When I was taking pictures after all the testing, I noticed that this one had turned from black to grey, so I decided to flick off the dome;
There was a crater inside the dome, but the phosphor was still surprisingly in tact, albeit a little burnt, possibly from being over-driven?
Test #5; Powered LED with dome perimeter cut, in boiling Prep-Sol.
Last test of the day, & I wanted to combine the best results so far. I used the Prep-Sol, as it appeared to have the cleanest result so-far, & I carefully used a razor around the perimeter of the dome, cutting in from the edge.
This time, I used a weaker battery, @ 3.65v.
The dome lifted, & "Clam shelled" as before, but still refused to come off completely by it's self.
This is probably the 2nd best effort, with #1 being the best of the bunch.
I'll install at least #1 into the Courui test mule, to see what the numbers are.
In the first round, I almost hit 400KCd, so maybe will be better this time. I'm not sure what can be expected in this setup out of the "new" XP-G2, but I'm guessing it's less than that, so already we may have a new thrower "king" by default.
The hurdle to overcome here, is that the phosphor is stuck to the dome almost as well as it is to the die.
I still have another five of these emitters, so will "sleep on it" for a while, before going in for the 3rd round...
:beer:
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Update; Installed LED #1 into the Courui, & after a bit of fiddling with shims, it was able to produce 410KCd.
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