What type of solder is best to use? I'm using a rosin base solder with 24ga. solid copper wire. No matter what I've tried, my solder will not stick. I'm refering to my Canon Owl PF shutter and common leeds. I've had no trouble with soldering the MS20. Yes, I've scratched off the green off the traces and tried wicking and tining the wire just won't stick to the shutter board. Please help... any suggestions?