That's about it. Generally speaking, what's used to attach the emitter to the PCB?
Usually it’s not directly attached. It’s attached to a pill which is connected to the PCB with wire.
if you're asking about a Cree emitter and a star PCB, it's usually reflow soldered with solder paste and a reflow oven. it can also be done with solder paste and a hot iron under the PCB, but if you do that you have to be careful you're using the right amount of heat. not enough and it won't flow properly, too much and you'll damage the emitter.
I only ask because farting around with a drop in I manged to detach the emitter by accident and I'm curious if I can reattach it to the MCPCB. I don't know what the little rectangular board the emitter is attached to, or if that is technically part of the emitter. Everything else is still attached. It's just the emitter that plopped off.
Unsolder and remove the PCB. Reposition the LED on the PCB. Hold the PCB with a needle nosed pliers and carefully heat the other side with a butane lighter. When you see the solder on the mounting pads melt, the LED will self align on the PCB. Immediately and carefully place the hot PCB on a damp sponge to cool.
I have overheated emitters and had them desolder you can use a butane torch like flash pilot said a hot iron or the easiest way I have found is to put the emitter in a frying pan and heat it on your stove until you see the solder liquify then let it cool and if its aligned properly it should work. I have an XML I overheated and fell off that I reflowed almost a year ago and it is still going strong.
I was just heating the pill with a soldering gun and it eventually plopped off. Mind you, I was using a 150w - 400w heavy duty gun. Also, I'm about as novice as you get with soldering :D I was only playing around with it because it's the under driven, 1-mode U2 drop-in I don't really have a use for. I had no idea reattaching the emitter is so complicated.
i want to see a pic : )
butane torch is a good idea . i used a propane torch it took less than a second , scary. cooled it down with a wet paper towel not pretty but it works. the excessive heat damaged the boards terminals and gooified the top coat. better than 12 bucks
I'm not sure I have the skills or materials to make this work.
When it came off it seemed like there was barely anything hold it on to begin with. It seemed like a sticky glue substance, but barely any.
you probably should have removed the led/pcb from the pill before heating the pill.
seeing a pic would be helpful in figuring out exactly what's going on.
if the emitter came off cleanly, you can just do the butane torch or frying pan thing and you should be able to reattach the LED no problem. the procedure would be to remove the pcb from the pill, apply a little flux to the pads on the pcb and the emitter (just a little bit), then heat the pcb until you see the solder flow, set the emitter onto the pcb (make sure it's properly oriented), then remove from heat. let it cool and then test. it should work as long as the emitter isn't damaged.
you can also take a 25-40 watt soldering iron and place it under the pcb to get it hot enough. the trouble there is finding a way to keep the pcb level for when you set the emitter on it.
I have reattached them all 3 ways frying pan is the easiest. Don't doubt yourself you can do this just make sure your wife doesn't catch you cooking flashlight parts on her good pans.
I have had two emitters fall off of their stars. Both KD U2?Dropins. I removed the star from the pill, cleaned all the paste from it, replaced the emitter and set the star on a hot frying pan. Slid it off in a few seconds and the emitter was soldered back on. First try I didn't leave it on long enough and it didn't stick. About four seconds worked. Have not had a problem with then since. No idea what the temp was. There are youtubes on this.