When removing a led and re-using the pad, is there a process to doing this? Should the old solder be removed before re-flowing it? For example, I was attempting my first re-flow the other day. All went well but it was slightly crooked on he copper sinkpad. I heated it again and removed it. Flowed it again and it was perfect, except later on I realized I put the positive and negative on backwards. I attempted to heat it again but it was stuck. I eventually got it off but broke it in the process. I grabbed another led but it would not flow. I eventually got it but one side was sticking up still, like it didn’t melt. I tried getting it to flow but needed up breaking that one as well. $10 down the drain!
Mike, if there's enough solder already on the emitter and pad you just need to add some flux then attempt to reflow again.
Yes. Add a dab of flux and try again. If the pads look dirty, wipe them down with alcohol first, then add flux.
Ok thanks. I was wondering if maybe I heated iy to much and it melted something off the LED. Idk, ill try the the alcohol next time. Maybe that will help.
Been there on putting the emitter on backwards 
If you did not heat it enough and had to break/rip it off, there is a good chance that when you got it off, it took the + or - pad with it. If it did, then it's shot. I have seen that before. The + & - pads are not direct, but sandwiched thin copper strip and they can get ruined. I would remove all the solder, clean it and look carefully at it. You can flux it, heat each pad and wipe the solder off with a rag or paper towel, by wiping as you pull the iron off the pad.
A good close-up photo might help us.
I made a 3rd attempt with it. It was still fighting me a bit, but eventually got it to flow. Hope it works. Dont have a driver to light it up yet.
Take a weak battery 3.6-3.7vdc, touch the leads to the pads, it should light immediately and very brightly…just don’t hold it down…this will let you know if you got it right or not…a fresh charged battery isn’t good direct drive…but a weaker soon to be need charging and quick bump will at least let you know
P.S. Don’t look directly at the emitter, otherwise you will get glare blinded…ask me how I know
I’m welder, I know all about looking at bright lights when your not supposed too. Lol