It’d be nice if it fit on a common Cree footprint so MCPCB’s were easy to come by.
Cree’s probably wouldn’t need a thermal pad at their rated specs either, but because they do we can overdrive them to the levels that make this hobby fun. Likewise I’m sure there is no need for a thermal pad at the Nichia’s rated specs, but it could have been much more fun if there was one. Time/testing will tell.
Direct XML swapping was in my mind…but I didn’t see that the Vf is 6V. It makes the swap more complicated.
Like DavidEF said, it’s more a XHP50 competitor
The 229A is 4.0mm x 4.0mm and ~3V. Not exactly XML size, but could be used for a swap. You’d need to replace (or mod?) the MCPCB anyway, since the Nichia doesn’t have the third pad in the middle for DTP.
There are ways for DTP with custom driver concepts:
a) Reverse the battery so that the body is + and can be electrically connected to LED+.
b) Use a high-side switch, i.e. a P-FET. These typically have a somewhat higher R_DS, but there are very good ones, too. LED- can then electrically connected to body (batt-).
So you would use short fat wires from the led into the copper star ?
And heat would go to the star ?
This would work with LEDs that also have a thermal pad. For turbo heat transfer.
Which would work better depends on which contact of the LED has better thermal connection to the die. It could end up an advantage, because packages like Cree uses must have internal insulating layers.
Djozz’s sketch would be great if the copper is thick enough.
A makeshift MCPCB shouldn’t be to hard for initial testing. Just use a Cree board whose anode/cathode footprints are close and grind out a little ditch where the thermal pad is with a Dremel, so there is no contact.
If they did a good design and uses the two main contact pads are the thermal conductors then the center pad should not be really needed. ( i guess most of us are used to having the center-pad on Cree emitters to match Noctigon stars, and like to over-drive LEDS to near burn-out. as long as the die, substrate, and two thermal/contact pads are designed well, and we have a good noctigon designed for these LED then where won;t be a problem.
So, if there is a dielectric layer under the electrical traces, how will a Noctigon help? This will be just like all the old Cree boards that have lesser thermal characteristics. The heat being dissipated through the trace pads will still have to go through the dielectric layer and as such, will be slowed down. This is ok if you don’t overclock, not at all conducive to most of us modifying flashlights.
Yeah, DTP stars are pointless if you’re not using the DTP! Best bet would be to make a board like djozz showed, with thick and large copper pours, and use the fancy nano dialectric layer that supposedly has a high thermal conductivity.
To simplify, 1D thermal resistance is a function of conductivity, layer thickness and conducting X-section area. If we’re stuck with using dielectric and copper, we can control 2 of those three variables.
Mitigate thermal bottlenecking by designing positive/negative copper pads as thick and wide as possible, instead of narrow traces. Heat flux can flow through larger cross section of dielectric layer.
Bottom layer is copper and thinner than than +/- pad layer.
For given dielectric layer thickness,
Larger X-section of dielectric -> smaller thermal resistance of dielectric layer -> smaller ∆Temperature across dielectric layer -> cooler temp @ LED die. It won’t ever be as good as true DTP but depending on PCB size it could approach DTP performance. Also, if it works well with 16mm board it will only do better at 20mm.