I use Radio Shack # 6400005 (formerly known as 64-005) solder on coils and on circuit boards.
https://www.radioshack.com/products/snpb-60-40-rosin-core-solder?variant=31204770021446
6400009 is the bigger spool of the same stuff.
https://www.radioshack.com/products/snpb-60-40-rosin-core-solder?variant=31204769988678