I use the thinner gauge solder. I also use flux as well. The solder I use has some silver content as well.

 

For electrical work, a rosin core solder is what you want, NOT AN ACID core. You could also add some rosin flux to what you are soldering.

 

Do not use acid flux. Get thin rosin multi core. Kester "44" .031" diam -https://www.amazon.com/KESTER-SOLDER-32117-24-6040-0027-Diameter/dp/B00068IJPO?th=1

 

I recommend this solder.

Kester 44 Rosin Core Solder 63/37 0.80mm (0.031 inches) 1 lb. Spool

63/37 is a eutectic alloy of tin/lead, and has a slightly lower melting point, (183 °C or 361 °F). However, more important is the fact that it goes immediately from a liquid to a solid at that temperature, this reduces the possibility of a cold solder joint.

 

I prefer the thinnest rosin core solder that I can find. Also I prefer to set my iron to 20 watt. Less likely to melt something other than the solder that way.

 

IMO, setting a soldering iron to a power setting as opposed to a temperature setting is far from ideal. The best solution is a temperature controlled soldering station where you can read the actual temperature of the tip and set it to the job at hand. Having a wattage setting will allow the temperature to be all over the map, based on the actual item you're soldering.

As far as the solder size, I use .020" diameter for PCB work and the .031" diameter for general wiring. One size doesn't necessarily fit all.

 

I agree with that for temperature. Unfortunately I have a set of two irons. One is set at 10 or 20 and the other is 15 or 30. They do the job so I never bought an more expensive station. Had the same irons as long as I can remember. Only changed the tips after years of use.

 

So happy the O.P. posted this question as I was going to ask the same one soon.

I couldn't imagine how long it would have taken me to use a 1 lb spool of solder so I tracked down the suggested Kester solder in a much smaller "beginner" quantity here :

https://www.cmlsupply.com/wire-solder/

Again many thanks again. Love this forum !!

 

I go through a roll within a year, so I always have one in the drawer ready for action.

 

Well, they've been working for you for years, so I can't argue that point. I just do a lot of PCB work, and some of the stuff is pretty small and delicate, so I need better control.