Visible phosphorus aging on cheap 10W COB LED modules.

     About a year ago now I tore down my old lab with the plans to rebuild it into something bigger and better. And today when cleaning up I found my old LED overhead light that I used to light up my workbench. When I looked at the LED modules I noticed something strange and decided to write a blog post about it. The strange thing I've noticed is what I assume is aging of the phosphorus gel used to convert the blue light from the LED chips to something more eye-friendly.

    The first picture below is one of an LED module that failed early (how typical of these COB's) and you can see that there's a little black halo around each of the LED chips but nothing more.



    Second picture is of an LED module that lasted much longer and you can see how the phosphorus has darkened and it almost looks like it has become more translucent. Also the dark area around each of the LED modules is much darker and bigger.

    In the third picture is the same old LED module just from a little further away for contrast. You can see that even with a very bright light the phosphorus is still very dark and in person looks more orange than yellow. Also there seems to be some corrosion spreading around the bondwires, unlike the lesser used LED module.

    This here shows that the phosphorus in these LED modules is subject to aging, although it took a couple years to get to this point.


Anyways, that's it for now and thanks for visiting my blog :)

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