Hi Eric, I was not able to find this plummers pastebut as you see I figured something else out
The flux plumbers use can be found even at Walmart. Can't imagine any hardware store not carrying it. You change a hot water heater, you need it. Air Conditioning lines are another very common use. It's not recommended for circuit boards, since the traces are very thin, doesn't take long to eat through or weaken them. Guess it doesn't matter now, but you could have saved some time and money.