On Monday, April 19, 2021 at 12:24:56 PM UTC-4, Peter W. wrote:
Well, to tell you the truth, I used to not worry about it either in the
days when I could get true 60/40 solder from Radio Shack, but those days
appear to be long gone.
60/40 solder from any source is wretched stuff. From China or not.

What you want is true eutectic solder, 63/37. Accept no substitutes. Plenty of US sources as well.
Peter Wieck
Melrose Park, PA

Just bought three pounds of vintage (BOW) 63/37 from ebay. $45 for all three including shipping, about as good as I can find.