Experiments in LED encapsulation

[bshanahan14rulz]

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

 

[saabluster]

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?

 

[AnAppleSnail]

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?

 

[saabluster]

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.

 

[bshanahan14rulz]

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).

 

[saabluster]

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.

 

[bshanahan14rulz]

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.

 

[cpf user]

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