How do i solder a XHP70 emitter to a massive copper bar

I have 4 pcs of XHP-70 emitters without the star/heat sink.
The easiest way to solder these to a solid copper heat sink by myself?
One solution would be a 12V XHP-70 on a 10mm copper base but i could not find that.

I don’t think you’ll be able to. The copper star has what amounts to a circuit board on the face of it and there are specific traces for current to flow through the LED. I think you may be out of luck trying to whatever it is your trying to do. Any way you can get a bigger copper heatsink?

I think an option would be to buy some DTP PCBs, then trim them to fit if needed, and solder the PCBs to the bar and then reflow the emitters.

I would drill/tap screw holes in the bar to keep the PCBs from floating during the reflow process. Also keep some ice/water handy to quench the heat asap, as reflowing on so much copper would require a LOT of heat…

Yeah there’s no way around a star. You’ll just short the emitter, especially with the way the pads are on the XHPs

After you get a pcb, flow the led with high-temperature solder paste, then solder the star onto the copper with the lowest temp solder paste you can find. If you use something like a toaster oven, you should be able to melt the low-temp stuff while keeping the LED firmly on place, and more importantly, below it’s maximum junction temperature for the long time that much copper takes to cool.

I found some stuff that melts at just under 300 F, which is like 140C. The LED should survive in theory.

Isn’t it easier to put the LED on a star and screw that on the bar with a little thermal paste underneath?

Yeah. But If you just really wanted to solder it……

sure you can do it, i do not see why not, people have been soldering many leds to copper pipes. this is not that different.

if you wire them all parralel, it is even easier, you can use the bar as negative, or positive “bus”, iirc heatpad in xhp70 is electrically isolated.
even if you wire them in series you can use the bar as 1 conductor.
thou they will be wired for 6v, not 12

however i do think, going with individual stars will be more convenient and practical, sure heat transfer will be not as good, but it still should be good enough