here's the list of good-quality 63/37 eutectic solder wires that will make your life easier when building and maintaining own builds (e.g., switches, leds, diodes, resistors). these brands and models produce good outcomes, based on my tests and experiments. my reference solder wire is kester with the stated specs below.

1. kester flux 245 core 58 0.6mm (flux % 2.2). it's the most expensive, with lesser flux remnants after work. still, it's better to clean it up with 99% IPA.



2. mechanic hx-t100 0.6mm (flux % 1-3). this one leaves excess of flux sometimes. (however it might be due to the way i handle it, e.g., feeding speed)



3. white monkey (白猴) 0.6mm (flux % 2.2). this one s not pretty in terms of packaging. basically it's just a green sticker with solder wire composition values stamped in red ink. however, it's one of the most recommended solder wires in mkb community in China. (sources: zf, bilibili, baidu)



they all have differences in smell and amount of smoke. none of them are pleasant. i don't go smell them so i have no comment. usually i use 0.6mm thick solder wires, because i'm used to it for switches and led. now i try to get used to 0.8mm also, for switch soldering. tbh, for this hobby, there is no need to get like the whole spool of 500g to 1kg. (unless you use them for other purposes that can consume them. solder wires do expire. while still usable, they're relatively not as good as new ones) 20g to 50g are sufficient for a few 60% builds. in this regard, mechanic and white monkey do come with smaller SKUs. just get a new one when they're finished.

yes, there are other alternatives, and some are more expensive options. however, for mkb modding, you don't need to go that far. also, you can choose for models that have less flux (like kester core 50, i.e. flux % 1.1) it's up to you.