All depends on budget most irons 25w or above will do the job. But knowing how to solder is the key. Always wet the sponge wipe the tip of the iron clean on the sponge and tin the tip of the iron with a small ammount of solder to give good heat transfer, then tin both surfaces you want to solder. Leaded solder is best (non rohs compliant) if you can still get some try and stay away from using a flux paste, If you really want to use flux then use a flux pen and then clean off the joints with motor cleaner once the soldering is complete. Flux is nasty stuff and will eat away at components over time if its not cleaned off. Hope this helps
