Role of the silicone on led core

[ergotelis]

Hello, a simple led question, what is the role of the silicone on the core of the led?
I have a Cree P4 with silicone removed and it is still working.Am i going to have any kind of problems?Is it going to die gradually?
The beam profile changed as i noticed.

 

[cdosrun]

Hello ergotelis,

I think the silicone is used for a number of reasons, it prevents contamination/oxidation and other damage to the phosphour coating (and I think some phosphours coatings can be toxic so this may also be a reason). I think it has a role in spreading the heat out a little around the phosphour to prevent greater degradation of some areas and then it also forms the primary optic of the LED to focus the light into the pre-defined area (around 70 degrees in the case of a Cree XRE).

There may well be some more reasons and I am sure someone else will mention them soon. However, I think the summary is that, yes, you will suffer from degradation of the LED of a quicker period than with the silicone coating.

Andrew

 

[ergotelis]

Hello ergotelis,

I think the silicone is used for a number of reasons, it prevents contamination/oxidation and other damage to the phosphour coating (and I think some phosphours coatings can be toxic so this may also be a reason). I think it has a role in spreading the heat out a little around the phosphour to prevent greater degradation of some areas and then it also forms the primary optic of the LED to focus the light into the pre-defined area (around 70 degrees in the case of a Cree XRE).

There may well be some more reasons and I am sure someone else will mention them soon. However, I think the summary is that, yes, you will suffer from degradation of the LED of a quicker period than with the silicone coating.

Andrew

Thanks ANdrew for the answer, really helpful!
The only thing that worried me is the fact that it is toxic, by what way is the phosphour toxic, by smell, touch etc?Could it be dangerous? Should i throw it away and replace it? That is the only really important that i didn't know and i am worried about it. WHat should i do?

 

[cdosrun]

I think the toxicity is from the heavy metal components of the phosphour. Ingestion or inhalation of the powder would be required if there was going to be a problem (assuming it is slightly toxic).

Personally, I wouldn't be concerned about one LED other than the practical aspects of severely reduced life expectancy and altered beam pattern. If it is still working then carry on with it until it dies or the output becomes too low for your use. What is the LED in?

Andrew

 

[ergotelis]

It is not on an expensive flashlight, it is a mod, a really nice one, will post some pictures later.I bought sku 3383 from dx, put on a cree reflector+an old cree P4 replaced from another flashlight and i made a really nice flashlight!Not something expensive, though light output is great, assuming that the led it is driven about 400mA(much better than jetbeam CL-E V1.2, about like fenix p1d on high) with a nice runtime , with a one minute charge it lasts for 10 minutes about on the highest setting and i guess some hours on the lowest mode.

Thanks again for your interest! :thumbsup:

 

[SemiMan]

It is not so much for focusing as it is for assisting with light extraction. It provides an optical interface between the die and the air around it. Without it, more of the light reflects back into the LED as opposed to exiting the surface.

For the CREE and others, it also protects the bond wires.

Semiman