I use plain old radio-shack solder, rosin core, lead-free, in the narrowest diameter they had without silver in it. It works pretty well. I also keep the larger size on hand.
For tricky soldering jobs, like where I'm soldering fine pitch SMD parts, or if the solder just doesn't seem to be wetting, I use "no clean gel flux". Tack part in place (soldering a corner or something) put a little on the pin and trace where you're soldering. Works miracles. This stuff: http://www.amazon.com/QuickAlloy-Flux-30cc-Syringe-Nozzle/dp/B00DAN3XHQ/ (note - there are other brands that are probably just as good. Also, the "single use only" on the syringe is not relevant - that's boilerplate on plastic syringes, since they're manufactured with medical applications in mind. It sure does raise eyebrows when people see the syringe, with blunt needle pointing up, sticking out of my pen-holder on my desk).
Despite the nice big pads, I found the bluetooth module to be surprisingly hard to solder onto the Espruino; I'd use the flux with it if I was doing that again, especially if I wasn't experienced with soldering.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
I use plain old radio-shack solder, rosin core, lead-free, in the narrowest diameter they had without silver in it. It works pretty well. I also keep the larger size on hand.
For tricky soldering jobs, like where I'm soldering fine pitch SMD parts, or if the solder just doesn't seem to be wetting, I use "no clean gel flux". Tack part in place (soldering a corner or something) put a little on the pin and trace where you're soldering. Works miracles. This stuff: http://www.amazon.com/QuickAlloy-Flux-30cc-Syringe-Nozzle/dp/B00DAN3XHQ/ (note - there are other brands that are probably just as good. Also, the "single use only" on the syringe is not relevant - that's boilerplate on plastic syringes, since they're manufactured with medical applications in mind. It sure does raise eyebrows when people see the syringe, with blunt needle pointing up, sticking out of my pen-holder on my desk).
Despite the nice big pads, I found the bluetooth module to be surprisingly hard to solder onto the Espruino; I'd use the flux with it if I was doing that again, especially if I wasn't experienced with soldering.