good thermal materials for boards are available up to 7-8 W (m*K). Your board suppliers should be able to order in for you.
I am not aware of any other manufacturer using this type of method as it is more costly than
just bolting down a MCPCB. As those of you making your own flashlights, this is one method
that you might consider. The circuit board that we use is designed only for electrical connections.
Curt
Just to report back that I received the DX copper star XML a short while ago, just got some time to play with it.
The led was visibly lifted from the board, there's a visible gap on one end, bad news if one want to use it "As is", may perform worse than a well done alu. star due to the "gap". Cutter leds are usually re-flowed on to the star with better quality job.
So I proceeded to a re-re-flow, added a little bid of solder paste to the gap side,
used a heat gun & managed to "close the gap".
Tested it on a big copper heat sink running between 5-5.5 Amp, so far so good.
Good thing you noticed the bad mount. One thing to keep in mind when doing your own reflow work is to make sure you don't have too much solder under the LED. You can tell if you do by pushing down on the LED while the solder is still molten. If there is too much it will squirt out as a tiny ball. Any more than necessary will increase the thermal resistance. Just keep it held down until it solidifies and then knock the ball away.
Thanks. I use needle nose to grab the star with one hand & the other hand blow from under with my heat gun, so my operation won't allow fingering from above . But it still managed to spit out a tiny solder bead, I watched the youtube video a while ago a guy was showing the heat gun method. looks like the surface tension is squeezing the excess out when solder melted down to liquid form. When I was done, it looks pretty tight, lot better than before.
BTW, this wasn't my first time, my 1st time using this technique was trying to mount
triple SST-90 onto copper, I ended up killing 2 out of 3 SST-90s.
. . . So although I see some role for surface tension in the fact that the two parts draw to one another I have not seen this be of sufficient strength to overcome the application of two much solder. . . .
That's part of the plan.Now, saabluster, you just need to sand an XR-E down to the reverse-polarity diode and test again!
No that will not have any appreciable benefit as the heat does not really travel laterally through the ceramic.hi guys.
i can no longer do prac but am still engrossed by these threads.
its a shame that cree dont supply the led on a larger piece of ceramic.
anyway when you mount the ceramic (what you guys call reflow ), which is just under 1 mm thick? , would it help to build a bead of heat conducting goo around the edge the ceramic tile, effectively conducting some heat thu the sides of the tile ? being pretty close to epicenter and all. if that tile is 4mm by 4mm by 1mm thats 16 mm sqared on the base and 16 mm squared on the vertical border surface.
gee i hope this isnt already in this thread somewhere .
cheers
from a comparison I did.Did a comparison of the Cutter XM-L boards and KD XM-L boards. Mounted a U2 2S XM-L to one of each PCB (reflowing onto pre-tinned pads with RMA flux)
Screwed the pcb to a heatsink I pulled from an old mobo for the mosfets, using thermal compound(one at a time of course). Ran each LED at 3.73A for 10 minutes to reach a somewhat steady equilibrium. I recorded the Vf at the power supply and light output on a lux-meter 6.5" away, neither the clamp for the heatsink nor the lux-meter moved between tests.
Even soldering the wire leads to the PCBs with them mounted to the heatsink, I noticed the KD board was harder to solder. I also noticed the heatsink became hotter much faster with the KD compared to the cutter PCB (hotter faster is good!)
Results:
*The Vf was at the power supply, not at the LED, so there is ~6ft of wire that is probably a touch small for 4A between the LED and the voltage measurement.Code:KD Cutter Initial lux 11.65k 9.17k T+10 Lux 10.31k 7.47k Lux drop 11.5% 18.5% Initial Vf* 3.78v 3.73v T+10 Vf* 3.70v 3.63 Vf drop .08v .1v
I think the results pretty much speak for themselves, the KD boards are the better of the two