I have a small table vise. I stick a wooden clothes clip in the vise and then put the star in the clip. I hold my 40w soldering iron tip to the underside of the start until I see the solder melt. Then I gently lift up the emitter with a tweezers gripping the sides of the emitter.
Usually before reflowing an emitter onto a star, I’ll check to make sure there is enough solder. If not I’ll use toothpicks to apply a bit of solder paste.
When done, simply use the tweezers to hold the star, while releasing the clothesclip. Then move the emitter onto the vise’s anvil. It should be cool enough to touch within 1 minute.
Been using this method for years with 100% success rate. Zero burnouts.
It’s a very late reply but I eventually found time to try this.
It was much easier than expected. I put the MCPCBs in a vice-grip, heated the underside with a cigarette lighter and just popped the emitters off and on with a tweezers. It was very simple and the emitters kind of ‘sucked’ onto the center of the MCPCB when the solder was hot enough. Both lights work after the swap and I don’t think I encountered any issues or damage.
I did it that way at first, but switched to using a piece of copper as a ‘hot plate’ because the cigarette lighter left black soot on the bottom of the MCPCB while heating. Now, it leaves the soot on the bottom of the copper ‘hot plate’ instead! Copper transfers the heat very well anyway. Plus, it’s quick and easy to move the MCPCB to the heatsink for cooling. I don’t want the heat to stay in the MCPCB or the LED too long.