A Perfect Dedome?

[Lightbringer]

@18sixfifty

However, consider this. A while back I bought a hundred XP-G2’s from the same supplier of the same bin. I de-domed around 90 of them successfully using the same method and each and every one of them had the same tint once de-domed. I remember them in particular because they came out with a rosy tint after de-doming them and I loved it.

Ooh, what bin?

@18sixfifty

I think there is a lot more consistency than you think when it comes to bins, so that it should be possible to find out if different chemicals change the tint or not. Wouldn’t you say that If I had de-domed half of this batch with Gas and got rosy tints and half with nitro and got green that it would in fact be the nitro that is the culprit?

Absolutely. That’s why we need the Scientific Method™.

If someone is going to dedome 100 LEDs, all from the same lot, maybe split them 50/50, gas one and nitro the other. Or whatever solvents you’d use. First spot-check the LEDs before dedoming to see if they hold up as far as being close in CT and tint.

Then compare the results. If one solvent gives a nice color and the other gives a horrid green tint, then we absolutely know that the solvent makes a difference.

@18sixfifty

Also considering that dozens and dozens of members here have all reported back on their results and have agreed that some Bins are nice after de-doming and others are not, wouldn’t this also suggest that Bins are fairly standard? Different people around the country get the same results from the same bins so that certainly makes it seem that the bins are fairly consistent to me.

But some get their LEDs from FT, others from KD, others from MTN, etc.

And an LED could be on the ansi-white chart on the rightmost edge of a 3A, and another on the leftmost edge of a 3D, yet look almost identical, despite different labels of “3A” vs “3D”.

Similarly, a bunch of 1Ds might be alllll over that patch that qualifies a 1D, one close to 1A, the other close to 2A, an other greener one close to a 1C. That’s what I mean about a range of CT/tint within a particular bin.

[Sledgestone]

Good find, Jared! :+1:

[JaredM]

That wouldn't be a bad experiment except for someone needing to use so many LEDs and taking so much time.

I think the simplest test to get a clue in on the question of certain solvents causing a green tint would be to sacrifice one or a few hot dedomed LEDs with a good tint and soak them in the 'bad' solvents like gasoline, then determine if the tint changes upon removal.

[Sledgestone]

I agree, that would be a definite way of telling if it makes a difference to the tint or not.

Now we just need to find someone who’s willing to do it

[Lightbringer]

@JaredM

That wouldn’t be a bad experiment except for someone needing to use so many LEDs and taking so much time.

Forgot who, but someone here mentioned doing a whole bunch at a time.

[MRsDNF]

@Sledgestone

How is the tint Djozz?

+1.

[Jerommel]

I have experienced a dedomed XP-E2 shifting to green quite a lot…
But then i remembered i didn’t rinse it with alcohol.
So i put it in the dedoming solution i had (terpentine, benzine, thinner, kerosine, petrol (gas) iirc) and after that rinsed with alcohol (i used bio ethanol).
It turned out better than it was.
But i have no pictures or measurements.

[Jerommel]

But shouldn’t we be looking for the best silicone remover?

[Sledgestone]

Well, that’s exactly what we’re doing

And right now my best bet is Toulene.

[Jerommel]

@Sledgestone

Well, that’s exactly what we’re doing

And right now my best bet is Toulene.

Thing is, toluene is found in what we call ‘thinner’ here, so why should we look for ‘nitro thinner’ if it’s the toluene we’re looking for?

[djozz]

@Sledgestone

I guess that you have a good point there, Lightbringer.

How is the tint Djozz?

I have not checked the tint, but it is a random cool white led from the spares box, the tint is relevant if I would have known the tint that I started with…

Edit: FWIW, I checked tint anyway: pretty good actually, not ugly green, must have been a tint on or under the BBL before the dedome.

[18sixfifty]

OK so the experiment with the solvent I had on hand didn’t work. Or should I say it was no better than hot gasoline or using acetone. So I broke down and bought some toluene and will try that and report back. I’ve got 50 of the SST-40’s showing up soon to experiment on. I’m making a TR-J20 for a member here and want to make sure that he gets 12 perfect de-domes in there.

On the bin that turned Rosy, that was quite a while back, I bought them on sale for cheap on one of the big aliexpress shopping days. That was back when XP-G2’s had just come out so for that time they were great but they wouldn’t be high bin enough for today, not compared with the S4 2B’s. Still I liked them a lot and wish that more of them would de-dome that color. They actually reminded me a lot of a nichia. The problem with ali-express buys are that you never really know exactly what you are getting. You might get lucky and you might not. So I haven’t bought from them in a long time.

[Sledgestone]

@Jerommel

@Sledgestone

Well, that’s exactly what we’re doing

And right now my best bet is Toulene.

Thing is, toluene is found in what we call ‘thinner’ here, so why should we look for ‘nitro thinner’ if it’s the toluene we’re looking for?

Mainly because Nitro thinner apart from toulene also contains several other chemicals that removes silicone. And also because there have been reports of very little green tint shift.

[MRsDNF]

Thanks djozz.

Your 50 x SST-40 order makes my order of 4 feel slightly insignificant.
Good luck.

[18sixfifty]

The toluene took the dome off very clean. I did slice the dome off pretty close to the bottom before soaking. I didn’t boil the emitter on a hotplate. I used the boiling water instead like I would with gasoline. It’s VERY clean. Perfect. Now I’ll build a light with it in a while and report back on the tint. And I’ll compare that tint with the tint from the Hot high octane de-dome.

So far so good, keep your fingers crossed for me.

[18sixfifty]

@MRsDNF

Thanks djozz.

Your 50 x SST-40 order makes my order of 4 feel slightly insignificant.
Good luck.

Thanks Steve. Well the toluene worked perfect and the tint change was minimal. I didn’t see any green in it at all.

[khas]

@Sledgestone

How much did you heat the mcpcb? Just enough to melt the solder under the LED or longer than that? And did you use a hot plate or iron?

I use this re-flow block I made for my soldering iron :

I really haven’t had time to redo the experiment but maybe one/two minutes in total ?, it was more or less trial and error if it was still green I gave it some more heat

@18sixfifty

The toluene took the dome off very clean. I did slice the dome off pretty close to the bottom before soaking. I didn’t boil the emitter on a hotplate. I used the boiling water instead like I would with gasoline. It’s VERY clean. Perfect. Now I’ll build a light with it in a while and report back on the tint. And I’ll compare that tint with the tint from the Hot high octane de-dome.

So far so good, keep your fingers crossed for me.

Great news thanks, twelve de-domed SST-40’s ? that’s going to be some kind of monster.

[Sledgestone]

@18sixfifty

@MRsDNF

Thanks djozz.

Your 50 x SST-40 order makes my order of 4 feel slightly insignificant.
Good luck.

Thanks Steve. Well the toluene worked perfect and the tint change was minimal. I didn’t see any green in it at all.

Good work! Luckily we have straight toulene to buy here in Sweden, so I’ll probably order some today. The thinner I use now is 80% toulene and 15-20% acetone and the dedomes I’ve done with it turned out too green. I’m suspecting that the acetone is the culprit as I’ve read that it might eat some of the phosphorus when used.

[Barkuti]

Been on a local supermarket a while ago. They now sell a “turpentine simile” whose composition is: C7 and C9-C12 alkanes in n-alkane, isoalkane and cycloalkane forms. Looks good to me, gonna get a bottle tomorrow. Half a litre for €1.60.

[Mitko]

Well, i hate to say it but Cree has changed the dome`s sillicone again……hard times for dedoming are comming folks…XPG2 and XPL are already affected but the change