copper or brass?

did get a bunch of cree led
whitch should be on a full copper pcb
http://www.cutter.com.au/proddetail.php?prod=cut1859
but when open the box it looks like it is brass instead of copper

do somone know if it is somthing special whit it?

i wantet copper före the better heat resistance 398 W·m-1​·K-1 instead of aluminum 238, but if its brass it only has 111

i have used lots of brass and lots of copper, but i newer have seen yellow copper

will take photo of it, but i ned the right ligth and som brass an copper to

Scrape the thin edge with sandpaper and dip it in lemon juice. Copper will tarnish very quickly. Brass will not. That said, the thermal resistance is usually Energy per Kelvin. The LED is around 2.5C per Watt (At 10W, the XP-L die will be 25C hotter than the contact pad on its heatsink). The flashlight is around 5-10 C/Watt (A 5-watt flashlight will get 25-50C hotter than the room). The metal choice is almost never the limit on thermal throughput in LED design......................(Line breaks escape me).............LED = 2.5C per watt, Star = 2.5C per watt... Your 10W XP-L is already going to be 50C over the flashlight heatsink. Regardless of whether the star is brass, copper, gold, or titanium.

Approximating a useful area of 4mm x 4mm, and a thickness of 1.6mm, the brass star would drop 22C at 6W, while the copper one would drop about 6. That's a difference of 16 degrees. Nothing to sneer at.

The stars probably are actually copper, just oxidized in a way that makes them look yellowish. Mine looked funny when I got them too. All you have to do is scrape away enough to see the underlying metal, and you should be able to tell easily if it is copper colored or yellow.

AnAppleSnail said:

......................(Line breaks escape me)..............

Click to expand...

I have lots of trouble (especially line breaks) with CPF using Internet Explorer under Windows7. Works great with Chrome.

I was able to copy a line break from Notepad and paste into the CPF editor, and it works.

did get them uncut from the board and did take a scrap bit and it looks like copper inside, so its ok, they probebly have coated it after it vas cut, thats fooled me

vill take a larger scrap bit and try som other things whit it

i havent calculated or tested eh copper k/w thing whit led, but i know that when i did try whit peltier fore many years ago it was much better to have a heat spreader betwen the peltier and a aluminum heatssink
and if you can buy better things whit no or litte more monye , why dont do it?

ok, its copper, did test it now, did mill a scrap pice to rectangular size and bournd off the pcb , weight it and measured it, 8.79 gram /cm3

thats good enoght fore me