Thanks Johnkey, I borrow your pic here…
The copper board works unexpectedly way better than predicted. From many tests performed in BLF, we knew the tighter the LED pitch the hotter it gets. Not only because the copper trace surface area needed to shed the heat from the LED base reduced, but also due to the “photon cross talk” as mentioned by Nichia in their application notes. The LED takes and recycle the photon from the neighboring LEDs and the stored photon, instead escaping as light flux, trapped and heats the phosphor layer. The same phenomenon known as back scatter lights in undeveloped light guide.
Previous 16mm x 1,5mm nanoceramic aluminum PCB (VR16SP4) maxed out at 11,2A. And that was with LED pitch 0,4mm. The other 21mm x 2mm (0,25mm LED pitch) nanoceramic PCB (VR21SP4) peak output maxed at approximately same 11A but it’s thicker and larger in diameter. New copper based VR16SP4 v.2 with 16mm x 1,5mm (0,2mm LED pitch) maxed at 11A! I underestimated it, and expected no more than 8A. At first I couldn’t believe it, because VR16SP4 v.2 also has reduced copper trace area for mounting clearance. And then, it uses “standard” IMS technology with more than double (50µm) the thickness of the nanoceramic MPCB NC MCPCB (20µm). The thinner the dielectric layer the faster the heat moves away from the LED base to the heatsink.
Below you can see the big penalty in output just by closing the gap down to 0,1mm in VR16SP4m. With wider LED pitch, quadtrix E17A should be able to reach at least 7A instead of 5,75A. But this reduction in output means wider optics compatibility and more importantly, more control over beam shapes. With VR16SP4 v.2 you can’t go too narrow or there will be “donut” hole in the middle of the beam. And OP/textured reflector or microlens (honeycomb/peebled/textured) TIR has to be used for narrower optics. VR16SP4m can use lighter texture OP reflector or finer microlens surface TIR. It also produce higher intensity beam (brighter hot spot).
Same 1000mA total input. Note how E17A have much higher luminance for farther throw
Note:
Due to complication in maintaining relatively constant and cool MCPCB temperature using total loss water cooling, clamping jig, etc… I could not directly measure the output. Ouput measured once at 100mA briefly to prevent heating the LED and the rest of the output numbers derived using the plotted lux measurements (TASI 632A). Measurement done in my DIY light box using Maukka’s calibrated lights.
[Clemence]