Hi Guys,
I know, that copper has double the thermal transfer ability (don’t know if its the right name for it) than aluminium, but does that make such a great difference for flashlights? Are there any tests on that or is it just common knowledge, that a copper mcpcb will always have x less degrees celsius, compared to a aluminium? Also, how big is the difference in light output and efficiency, if the emitter runs above mentioned x degrees lower?
I am sorry if this is a dumb question, but i am a newbie to flashlights.
Greetings from germany, Devryd
The main difference why copper is preferable for a PCB is that you can solder to it, on the direct thermal path (DTP) boards the thermal pad of the led is directly soldered to the core of the board.
But Sinkpad made a series of aluminium DTP boards that at normal led powers (I tested them at 10W a few years ago) perform virtually identical to the copper variant.
For abnormal led powers copper will be a bit better than aluminium.
One nice thing is that copper DTP boards are now industry-standard for most mid and high end flashlights. Only the cheapest lights seem to still routinely use aluminum PCBs.
To add to djozz’s comment: In case you were not aware, whether the MCPCB has a direct thermal path or not is typically more important than the material. I think most Al MCPCBs you see are not DTP (unless they are sinkpad brand) and so would typically not perform as well.
But if I would use this LED (https://www.fasttech.com/products/6094902) in a normal, single 18650 flashlight, I still should be fine?
I mean, I would have better thermals with a copper mcpcb, but it should be usable.
how do I know, whether it has a direct thermal pass?
that is easy to check, heat pad and bottom of the mcpcb have to have continuity.
Sorry, could you explain this again? I don’t understand, what you want to tell me here.
There is not an easy way to tell from the picture and it doesn’t say in the description. It is prob not DTP. If you stay below about 3A there shouldn’t be a problem.
the highest amp driver I ordered has about 2.8 amps, so it might be close. How do I know, whether it is too hot?
It will be uncomfortably hot to hold. Warm or slightly hot is fine. But when it is about to hot to hold you have to remember there is a battery inside that’s getting hot also.
We use to use 3 amp lights all the time before DTP came out, so you should be fine at that level but I would still be a little cautious about laying it down in high.
Different lights will react differently with the heat, so its best to get a feel for the light knowing how your particular light will cope with the heat in what mode you use.
There are also some very good alu MCPCBs from Virence and Led4Power. They are not DTP but performance-wise they are almost there, good enough even for hotrods. And they weigh less. 
Use DMM to check short-circuit between central led pad and pcb bottom.
For low powered LEDs there is no significant difference.
If you’re pushing an LED at high currents for max lumens or throw then yes copper makes a huge difference to the die temperature, because all the heat needs to leave the LED through a small pad area only a few square millimeters big.
You will always loose Lumens even at 2.8A a XPL might loose 5-10% because it runs significant hotter on non DTP boards
Good to know kiriba-ru!
Just how big is the difference between the two? I am planning a custom mcpcb for a FWAA, supposed to run 3 519A at approx 1.5A each (until thermal stepdown of the host kicks in). Would that still be feasible with alu, or would me LEDs overheat and get damaged before the host can even try dissipating the power?
Alu vs DTP copper is ~ a factor 10-20 in price…
Just an opinion, havent tried it, but I guess you should be fine. 1.5A per emitters Isnt that much current and its spread out over a bigger space than with one emitters at 4.5A so I think Aluminium should be fine.
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mpcb copper, tutti il resto è meglio alu
praticamente il rame porta via meglio il calore ai led, però quando poi è il momento di raffreddarsi è bollente e ci mette un secolo a raffreddarsi (mentre l’alluminio anodizzato si raffredda prima)
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The host will be alu, I’m just modding an existing light. The question is just if I can get away with alu for the LED PCB or not. Alu costs 4$ for 5pc, copper 50-100$ for 5pc depending on how exactly jlc bills me for PCB with frame.
If I can get away with alu without frying my LEDs, that’d save me a ton of money.
Since FWAA can only sustain ~300lm without overheating, and I don’t want to go super crazy on turbo (my cell can’t supply over 4A) I hope alu will work.