Don’t underestimate the heat SINKING properties of aluminium compared to copper.
You can put much more heat in a given mass of alu than in the same mass of copper, before it actually gets hotter / warmer.
I have tried to explain that one before, but there is the widespread misconception that more mass means more heatsinking. If you compare copper and aluminium by volume (that is what you do in practice when you swap aluminium parts for copper parts) the copper part does win for storing heat, but only by a factor 1.4 compared to aluminium (while it is 3.3 times as heavy).
I didn’t know copper is better per volume as a sink !?
Thanks.
1.4 correlates well enough with this data.
I don’t think we should emphasize mass too much, volume is the factor is most cases, unless you’re flying it to space or something. So copper still have the edge hands down in most applications.
Copper pills are highly overrated. Unless you believe in them. There seems to be many believers though. The measured differences are usually between zero to minor depending on the current in a typical XM-L2 hotrod build.. In a fully hotrodded MT-G2, there is more gain, due to having up towards 3-5 times as much heat going through the MCPCB and into the pill, but even then. Not really noticeable by eye..
If id had not been for the copper hype here on BLF, the difference between the best copper and aluminium MCPCB would`t be as shocking to some..
'Copper is better than ___!!!' has turned into some kind of cargo cult.'But I build all my lights with copper everything, and they are all really bright, therefore if you want it to be bright you have to use copper!'
The numbers just don't back up what you find in those thermal conductivity charts. They're irrelevant.
We've kind of blasted brass as being the worst thing possible, now sinkpad uses a 135W/m.K rated aluminum for those boards, most likely 5052 which is the most common specified alloy in alu MCPCBs, now we have the "poor" common brass at 125W/m.K....
Is there a chart anywhere that shows how many lumens per W/mK? No? Why not?
"My dog thinks that if he barks at a telephone he can make it stop ringing. Since the phone does eventually stop ringing, that proves he's right."
Outside flashlight world, brass is considered a high thermal conductivity material actually. Also I remeber 7075-T6 aluminum which is a really strong alloy also being kind of blasted for being only 135W/m.K rather than 160W/m.K like 6061-T6.
“My dog thinks that if he barks at a telephone he can make it stop ringing. Since the phone does eventually stop ringing, that proves he’s right.”
lol!
So never mind the artificial diamond then, the kind that conducts heat several time better than copper, yet does not conduct electricity.
I forget how it’s called…
It’s not even that expensive though.
No, if you're talking about what's right below the tiny little thermal pad of the LED, that's different. Much smaller area, so the material (or presence/lack of dielectric layer) does make a difference. But the contact area between MCPCB and pill, and between pill and light, is so much larger by a factor of whatever, that the thermal performance of the materials really makes very little if any difference.
It’s called CVD
You can even buy small discs via AliExpress.
No dielectric layer needed as it’s an electrical isolator.
The cutter MCPCB being discussed earlier uses a DLC layer to bond the copper traces on top (which will readily accept solder) to the aluminum substrate (which will not readily accept solder). If the base material can be soldered to directly, there is no need for a dielectric or any other kind of layer inbetween.
Is this a quote from somewhere?
Yes, but I can't remember from where. It's one of those things I stuck in my 'stuff I might find useful someday' text file and I didn't include the source.
google had no clue, buts it applies to so many things in life that i want to quote it elsewhere
For some reason BBC's 'Surviving Progress' keeps popping into my head, but I'm pretty sure it's not from that but something similar.
edit: No, scratch that. I went back and checked where that line was in the list, and it most likely was a comment from some anonymous person on a post at Wonkette.
I’m looking for info on Sinkpad2 Rebel boards — I got a few 20mm samples (they’re aluminum), but have been wondering if I can cut them down to 16mm rounds without blowing up anything important.
(or of course if there’s a simple answer — 16mm boards to fit Rebel emitters)
EDIT: I might’a’known someone already tried carving down a Sinkpad; I’m guessing this will work for the Rebels also: SOLD: RGBW SinkPads for Color XM-L and Luxeon Rebles <---- They are here!!!!
As long as you dont cut the trace between the 2 little foot pads for the battery + and -.
If you leave part of the outer square + and - pads ( like if you only cut the board down to 16mm) it should be ok.
Or if you do have to cut in deeper for like a 12mm. Then you would need to expose the traces that come from the smaller foot pads so you would have something to solder the wires to.