This 5W COB (Chip on Board) LED has a circular layer of phosphor impregnated jelly poured over the array of LEDs. It's very obviously yellow, so it's possible the LEDs are blue or UV. Is it possible to peel back the phosphor and reveal the LED colour?
By Julian
Youtuber, shed dweller, solar charge controller aficionado
The LEDs are dying because the manufacturing process attaches the top side of the chips with a micro-wire, and pulling the phosphor off rips off the wires.
Why would they use a blue for the white LED instead of the ultraviolet one?
looks dumb
Ok folks he is onto something, you need to start using your own mind, get a blue laser and any fluorescent yellow material. if you use a uv laser , you will need blue and yellow fluorescent. the more powerful the laser, the brighter the light. now take this old but new found knowledge and create something.
Usually it's royal blue LED's. If the die is big enough you can try to remove one of the dies from the phosphor and light it up with sharp multimeter probes against the pads using continuity/diode mode on the multimeter.
Utterly horrid! Who is this bloddy idiot! First disconnect the two 9V botrreys (how the Brits pronounce batteries, BTW…). Then yew (how the lil people across the pond pronounce 'you') take acetouuune (that's acetone in Brit speak) to the epoxy resin to weaken it. Afterwards, a short blast of high-pressure air remeuuuuvs the phosphor coating that had been weakened by the acetone, leaving all SMT components perfectly in place. A nice and clean result that would take less than 30 seconds of YouTube time.Did it, done.The American way. ;p
the peak on the spectral curve shows the excitation wavelength of around 450 nm
They are blue. I recently saw a teardown video of a led bulb where the yellow phosphor was in 4 parts that clipped around a central hub of blue leds. The phosphor coating on the plastic surround then glowed when the blue wavelength of light hit it.
Good idea – but I'd need a microscope!
You could try to contact one led chip with a needle after removing the phosphor.
I agree.
Should be blue
I'm sure you're right. I didn't really expect this to work – but it'll be fun trying. Power control will have to be constant voltage. If I use constant current and one series string fails, the others will go over current and fail too – a cascading failure.
I'm going to try again – by letting the LED overheat in the hope the phosphor will either melt or burn away. Should be fun!
You never know till you try. Bad luck.