I don’t know if this has been brought up before or if it’s common knowledge but it’s somewhat of a community announcement.
I recently bought a few led’s from kaidomain and most of them arrived on copper stars. I took off an sst-50 to mount on something else and thought since the star is not in use why not check it out. Just as I suspected the copper is just a direct replacement for aluminium and is not a sinkpad, there is an MCPCB layer over the whole star. Whilst it might transfer the heat a little better than alu it cannot be compared to a sinkpad so don’t be fooled. Kaidomain is actually one of my preferred chinese vendors and they don’t claim these to be sinkpads but it is easy to make the wrong assumption.
If these pics show up properly you’ll see the copper solder pad ring around where I scratched it. In the second shot I circled where I scratched through to the copper star.
FastTech sells these too and some lights ship with them. Awhile ago, I bought a couple just to see. You can grind/sand off the layer and get a cheap SinkPAD style, but then you have to fill that hole back in with solder. I've had troubles reflowing this setup -- can't get the LED to sit down even. Either too much solder or too little - dunno, I found it very hard to get right - don't think I ever did. I never compared head-to-head against alum and SinkPAD's, but the most common opinion is it's somewhere in the middle.
SinkPAD (SinkPAD.com) rates their aluminum direct path XML star for thermal conductivity of 135.0 W/m.K, while the copper direct path XML is rated at 385.0 W/m.K. Not sure what this means in "real world" use for us...
A dielectric layer on top of copper or a dielectric layer on top of aluminum, I think it's probably a waste of good copper. You could put a LED and a dielectric layer on pure diamond and it still wouldn't help.
These types of stars are why I hate when people suggest that manufacturers put their LED's on copper stars. That's worthless unless it's a direct bonded copper star, and that really needs to be said when these suggestions are made. Direct bonded copper or don't bother.
SinkPAD's site (http://www.sinkpad.com/what-is-sinkpad.php) says the average star is 1-4 W/m.K, and the aluminum SinkPAD is 135 W/m.K, then copper SinkPAD is 385 W/m.K, so the major improvement is removal of the dielectric layer.
In their presentation (http://www.sinkpad.com/sinkpad-presentation.php) interesting in that they identify a "thermally conductive" dielectric. They call it MCPCB Type 2. So it appears there is difference in the stock aluminum stars out there, and even if they have a dielectric layer, it could be a "good" one or "bad" one.
Everything I see on their site is saying the aluminum SinkPAD is the same exact design as the copper one, just different base metal used.
Since comfy frequently brings up how copper pills don't work any better than aluminum pills, I wonder if the same would be true with direct bonded mcpcb's. I'm betting testing would come up with the same results for both aluminum and copper direct bonded mcpcb's, but I'm rooting for copper.
Since comfy frequently brings up how copper pills don’t work any better than aluminum pills, I wonder if the same would be true with direct bonded mcpcb’s. I’m betting testing would come up with the same results for both aluminum and copper direct bonded mcpcb’s, but I’m rooting for copper.
Using copper on a PCB definitely shows output improvement, mostly because the heat density is much higher compared to a pill. Match’s tests:
But is that improvement from the copper or from the elimination of the dielectric layer… that the improvement exists isn’t the question.
Whoops, that’s true, sorry about that.
I vaguely remember a discussion that concluded that copper PCB’s with a dielectric layer was similar to an aluminium PCB rather than a SinkPad/Noctigon.
I have 10 sinkpads that I got as free samples, some aluminum and some copper. Does anyone want a copper XM-L and an aluminum XM-L bare sinkpad for some testing? Shoot me a PM, and I’ll try and hook you up.