HDS Systems
Page 3 of 3 FirstFirst 123
Results 61 to 88 of 88

Thread: Experiments in LED encapsulation

  1. #61
    Flashaholic*
    Join Date
    Dec 2008
    Location
    Sydney, Australia
    Posts
    1,064

    Default Re: Experiments in LED encapsulation

    *BUMP!*

    Hi Saab, you're probably busy with making Deft FTPs, but have you had the time to experiment further with these?
    Finning does help dissipate heat. This is why the fins are removed before cooking fish. Otherwise it will throw off the heat and not reach the proper cooking temperature. --Duglite

  2. #62

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by Th232 View Post
    *BUMP!*

    Hi Saab, you're probably busy with making Deft FTPs, but have you had the time to experiment further with these?
    No I have been pretty focused on the DEFTs of late. I have some ideas I want to try so I am not done with this thread. Will update when I can get to them.

  3. #63

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by saabluster View Post
    Even if you remove the silicone gel from off the top of the phosphor the phosphor itself is not coming in contact with air. The phosphor is suspended in a silicone elastomer that acts as a binder.
    1. Am I right in thinking from the above, that the LED can exist happily (or happily enough) without a dome and the silicone gel if hidden behind a lens and mount?

    2. Do you or anyone have a domeless & gelless emitter with lots of hours on it, if so, OK?

    3. I have a damaged dome on an XP-G where an XR-E would have been a better choice. Do you or anyone know of anything about an XP-G (other than wasn't the best option to start with) that might be an issue, if I remove the dome and gel rather than replace it?

    Quote Originally Posted by saabluster View Post
    You may notice that relatively few people come down here to the LED section. It is a place for LED geeks of which group I claim to be a part. Few people here truly understand the magnitude of what's been accomplished here but I'm fine with that. Thanks for noticing.
    Awesome.

    Started with LED MR16 plug ins...and in a few months, I'm thinking of modding an LED to get the beam I want.


  4. #64

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by BrianMc View Post
    1. Am I right in thinking from the above, that the LED can exist happily (or happily enough) without a dome and the silicone gel if hidden behind a lens and mount?

    2. Do you or anyone have a domeless & gelless emitter with lots of hours on it, if so, OK?

    3. I have a damaged dome on an XP-G where an XR-E would have been a better choice. Do you or anyone know of anything about an XP-G (other than wasn't the best option to start with) that might be an issue, if I remove the dome and gel rather than replace it?



    Awesome.

    Started with LED MR16 plug ins...and in a few months, I'm thinking of modding an LED to get the beam I want.

    Although I haven't done the thousands of hours testing that would be needed to qualify parts to be sold without the outer layer of encapsulation on XR-Es I have not seen any issue in the tens of hours. I have not spent any time tearing down the XP-G however and I am not sure how the phosphor is applied so really have no basis for whether or not it will work without the dome.

  5. #65
    Flashaholic panicmechanic's Avatar
    Join Date
    Nov 2009
    Location
    Germany
    Posts
    130

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by BrianMc View Post
    Started with LED MR16 plug ins...and in a few months, I'm thinking of modding an LED to get the beam I want.
    ...and you'll be reading stuff like this

    Pity they haven't analysed the XP-G yet.

  6. #66

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by saabluster View Post
    Although I haven't done the thousands of hours testing that would be needed to qualify parts to be sold without the outer layer of encapsulation on XR-Es I have not seen any issue in the tens of hours. I have not spent any time tearing down the XP-G however and I am not sure how the phosphor is applied so really have no basis for whether or not it will work without the dome.
    Thanks. Had to ask in the off chance you had.

    No point in going where someone has found it to be unwise.

    If the domeless XR-E's don't self destruct for at least 10's of hours I might get couple of months on flash in the day, a couple of weeks of night rides. Sounds worth a shot but AFTER I have an XR-E or three on hand, just in case.


    Great stuff. I'll be watching.


    Anyone else reading this, had any experience running domeless XP-G?

  7. #67
    Enlightened Neondiod's Avatar
    Join Date
    May 2009
    Location
    Sweden
    Posts
    73

    Default Re: Experiments in LED encapsulation

    I think this can be called a "throw job"

    Quote Originally Posted by clint357 View Post
    Do you think there is a chance that you could get a usefull beam from just an LED with the modded encapsulant? That would be awesome to be able to just stick a new dome on an LED and put it behind a flat window for a medium beam and then have the option to throw an aspheric in front of it for a laser.
    That's means back to basic 5mm led design.

  8. #68

    Default Re: Experiments in LED encapsulation

    A point of clarification:

    [QUOTE=saabluster;3315866]Although I haven't done the thousands of hours testing ...without the outer layer of encapsulation on XR-Es, I have not seen any issue in the tens of hours. QUOTE]

    This infers that you have some XR-Es reencapsulated as per your original post, and some "runnnin' 'roun' nekid" (domeless) with a some tens of hours of run time? No issues means no tint shift either?

    Is so, VERY interesting....

  9. #69
    Flashaholic
    Join Date
    Jan 2008
    Location
    Michigan USA
    Posts
    466

    Default Re: Experiments in LED encapsulation

    Looking at these experiments a few questions comes to mind. There has to be a difference in the index of refraction between the three materials present here. I would like to think that the acrylic optic lens has a lower number than the dome or the silicon encapsulant. I also notice that the over all height profile of the emitter is slightly shorter with the acrylic optic lens in place. The photons have less material of possibly a lower index of refraction than original. I think you have changed the degree of dispersion is a desirable way. The real scary thing is you got it in your first try. Have you any information on the index of refraction of the three materials? Is the silicon encapsulant you used as good as the original dome material? Looking at the last two photos in post #38, the projected image does look brighter but also a bit smaller. Just wanted to confirm that the distance was the same between light and target. Thanks for sharing your results, very interesting stuff.

  10. #70

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by BrianMc View Post
    A point of clarification:

    This infers that you have some XR-Es reencapsulated as per your original post, and some "runnnin' 'roun' nekid" (domeless) with a some tens of hours of run time? No issues means no tint shift either?

    Is so, VERY interesting....
    The only tint shift I have seen occurs immediately after de-doming the LED. I have not seen any addition shift in my naked XR-Es with time on them. One thing that can be a problem though is that with next to nothing covering the die some pieces of dust that may land on top will burn due to the intensity of the light so close.


    Quote Originally Posted by Fulgeo View Post
    Looking at these experiments a few questions comes to mind. There has to be a difference in the index of refraction between the three materials present here. I would like to think that the acrylic optic lens has a lower number than the dome or the silicon encapsulant. I also notice that the over all height profile of the emitter is slightly shorter with the acrylic optic lens in place. The photons have less material of possibly a lower index of refraction than original. I think you have changed the degree of dispersion is a desirable way. The real scary thing is you got it in your first try. Have you any information on the index of refraction of the three materials? Is the silicon encapsulant you used as good as the original dome material? Looking at the last two photos in post #38, the projected image does look brighter but also a bit smaller. Just wanted to confirm that the distance was the same between light and target. Thanks for sharing your results, very interesting stuff.
    I do not know what product Cree uses so it would be kind of difficult to know what was better or worse. I also will be keeping the specific material I used to myself for now. Yes that second shot is both more intense and smaller which was what the aim of this project was.

  11. #71
    Flashaholic
    Join Date
    Jan 2009
    Location
    Bristol,UK
    Posts
    144

    Default Re: Experiments in LED encapsulation

    Just thought I would chip in here after being pointed this way by BrianMc.

    I've been running a couple of (unintentionally) de-domed Rebels in one of my bike lights for more than a year. They still work fine, BUT I haven't done any other testing other than checking they still come on and look bright.

    For other (intentionally) de-domed Rebels, it is possible, if one is careful, to shear the dome off just above the LED die and still leave a small covering of silicone over the die, so in theory at least, the die should still have some protection from moisture etc. I'll try to get some pictures to show this.

    The die uncovered die is 1mm x 1mm, where as the covered die appears ~1.4mm x 1.4mm. In projected images, the uncovered die provides a proportionally smaller image, with slightly better definition - noticeably brighter.

  12. #72

    Default Re: Experiments in LED encapsulation

    How much brighter? It's clear that more light will be TIR trapped.

  13. #73
    Enlightened Neondiod's Avatar
    Join Date
    May 2009
    Location
    Sweden
    Posts
    73

    Default Re: Experiments in LED encapsulation

    Hello!

    I want to do the opposite. I want to mount a dome on a PLCC6 package to focus the beam a bit. I think of cut of the top of a generic 5mm led and glue it with epoxi on top of the PLCC6. When I saw of the top of the 5mm it will probably be an uneven surface. Do you think this will be a problem or is the epoxi going to fill out the grains and make the package look clear?

    TIA
    Last edited by Neondiod; 03-19-2010 at 08:14 AM.

  14. #74

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by Neondiod View Post
    Hello!

    I want to do the opposite. I want to mount a dome on a PLCC6 package to focus the beam a bit. I think of cut of the top of a generic 5mm led and glue it with epoxi on top of the PLCC6. When I saw of the top of the 5mm it will probably be an uneven surface. Do you think this will be a problem or is the epoxi going to fill out the grains and make the package look clear?

    TIA
    It very well may be a problem if you cannot find an epoxy that has a refractive index that matches the epoxy dome. It will reduce the output of the LED. You could use the lens off the top of an XR-E which is glass and relatively smooth on the back side.

  15. #75
    Flashaholic*
    Join Date
    Oct 2009
    Location
    Seattle,WA
    Posts
    2,470

    Default Re: Experiments in LED encapsulation

    Interesting thread.

    I don't think this question has been answered directly but maybe it has...would removing the dome from a XR-E and doing nothing else improve throw noticeably in any light with an aspheric lens?

    For instance, with the DX flood-to throw that everyone is familiar with what effect would just removing the emitter dome of that light have?

  16. #76

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by gcbryan View Post
    Interesting thread.

    I don't think this question has been answered directly but maybe it has...would removing the dome from a XR-E and doing nothing else improve throw noticeably in any light with an aspheric lens?

    For instance, with the DX flood-to throw that everyone is familiar with what effect would just removing the emitter dome of that light have?
    Yes it should improve throw. Maybe... The problem with the XR-Es is getting it to pop off cleanly. All too often the gel will tear and then you start losing lumens fast like. I would guess you could have up to a 40% increase in intensity if it was removed perfectly. Just a guess.

    The end result of this in a reflector would be a smaller and more intense hotspot with a dimmer spill.

  17. #77
    Unenlightened
    Join Date
    Nov 2011
    Posts
    1

    Default Re: Experiments in LED encapsulation

    Hi everybody, very interesting.
    Can someone tell me a good and not expensive optical grade silicone?
    fdrk

  18. #78

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by fdrk View Post
    Hi everybody, very interesting.
    Can someone tell me a good and not expensive optical grade silicone?
    fdrk
    None, not trying to be a nay sayer, but Ive looked long and hard and couldnt find anything, its pretty much dow corning or bust. and the dow corning silicone is $400 for 1L part A, and $400 for 1L of part B IIRC. Ive toyed with some optical epoxy from expoxies.com, and it was looking like I was going to have CTE problems, or long term bonding problems.

  19. #79

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by fdrk View Post
    Hi everybody, very interesting.
    Can someone tell me a good and not expensive optical grade silicone?
    fdrk
    You can have good or not expensive but not both. Here is some that is as cheap as you will find anywhere.

  20. #80

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by saabluster View Post
    You can have good or not expensive but not both. Here is some that is as cheap as you will find anywhere.
    Hey, thats pretty new, I was all over smooth-ons website looking at other products for the longest time. Neat find, wonder how it compares in layers that arent just a thin coat.

  21. #81
    Flashaholic* bshanahan14rulz's Avatar
    Join Date
    Jan 2009
    Location
    Tennessee
    Posts
    2,765

    Default Re: Experiments in LED encapsulation

    Saabluster, in your testing of these LEDs, did any of the LEDs' phosphor layers seem to be more resiliant and resistant to self destruction?

  22. #82

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by bshanahan14rulz View Post
    Saabluster, in your testing of these LEDs, did any of the LEDs' phosphor layers seem to be more resiliant and resistant to self destruction?
    What form of destruction are you referring to?

  23. #83
    Flashaholic* AnAppleSnail's Avatar
    Join Date
    Aug 2009
    Location
    South Hill, VA
    Posts
    3,912

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by saabluster View Post
    All too often the gel will tear and then you start losing lumens fast like.
    I have heard rumors that domes come off more easily with a heated LED. Do you know if this is true? Should I plug in my own toaster oven and start testing?
    My biggest light-hog is my camera.

  24. #84

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by AnAppleSnail View Post
    I have heard rumors that domes come off more easily with a heated LED. Do you know if this is true? Should I plug in my own toaster oven and start testing?
    I haven't noticed a dramatic effect but yes heat does help soften the rubber a bit. With the elastomer type anyway. No heat necessary for the glass/gel type like the Luminus and XR-Es.

  25. #85
    Flashaholic* bshanahan14rulz's Avatar
    Join Date
    Jan 2009
    Location
    Tennessee
    Posts
    2,765

    Default Re: Experiments in LED encapsulation

    I was wondering if you knew if one line of LEDs' phosphors are more robust than others, in such a way that the package fails (bond wires, emitter die damage) before the phosphor does (blackening).

  26. #86

    Default Re: Experiments in LED encapsulation

    Quote Originally Posted by bshanahan14rulz View Post
    I was wondering if you knew if one line of LEDs' phosphors are more robust than others, in such a way that the package fails (bond wires, emitter die damage) before the phosphor does (blackening).
    Your not being specific enough in the conditions you are referring to. Are you talking about in an overdriving situation or physical destruction methods such as removing the dome? The Cree gel/glass type packages do not seem as robust as the newer full elastomer silicone packages. The burnt phosphor seen on many overdriven XR-Es is in actuality the gel burning not the phosphor.

    Here's some pictures to show you what I mean.



    Notice that the burnt part extends past the boundaries of the die itself?



    Here you can clearly see that the gel itself is burnt.


    To know for sure it it the gel and not the phosphor we need to remove the gel over the die.

    I didn't get it completely clean but you can clearly see the burnt part is primarily in the gel. I have yet to see this type of damage on the newer XP type packages. The elastomers seem to have better heat resistance than the gels.

  27. #87
    Flashaholic* bshanahan14rulz's Avatar
    Join Date
    Jan 2009
    Location
    Tennessee
    Posts
    2,765

    Default Re: Experiments in LED encapsulation

    This is great news! I was referring to overdriven situation, but now I see that really I should have been asking about both. It would appear that the optical potting fails before the phosphor in overdriving situations in the gel/glass pictures. Those pictures are just what I needed. Looks like I'll need either an XP package, or a very-well cleaned XR.

    Thanks for those pictures, they do a great job of showing exactly where the damage was done.

  28. #88

    Default Re: Experiments in LED encapsulation

    Here is what seems to be new evidence of failure caused when potting contacts a silicone dome:
    http://www.cree.com/products/pdf/xla...mical_comp.pdf

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •