SDG #079 What's the best solder for electronics? Expensive or cheap?

Solder wire is the one consumable every hobbyist buys repeatedly, and the price spread between a no-name reel and a branded one from a company like Multicore or Kester is large enough to be worth questioning. This comparison puts cheap online-marketplace wire, including Mechanic-branded leaded solder and Pro’sKit wire, up against established names such as Multicore 502 and 362 and Kester, to find out where the extra money actually goes.

The important variable is not really the alloy. Most of these wires are conventional 60/40 or 63/37 tin-lead, and once molten the joints they form are broadly similar. What separates them is the flux core: how much of it there is, how consistently it is distributed along the wire, how aggressively it cleans oxidised pads and legs, how much spitting and spatter it produces, and how sticky or corrosive the residue is once the joint has cooled. Cheap wire often has flux voids or inconsistent flux percentage, which shows up as joints that need reflowing, poor wetting on older through-hole components, and residue that is harder to remove with isopropyl alcohol.

Microscope inspection of the finished joints makes the differences easier to judge than eyeballing them at the bench, and the residue left behind is examined after cleaning as well. For most general repair and prototyping work, mid-priced wire in a decent diameter around 0.5 to 0.7 mm is the sensible purchase; the very cheapest reels are a false economy when a bad joint costs you diagnostic time, while premium branded wire mainly buys consistency and predictable flux behaviour rather than a dramatically better joint.