Hello, I am writing because when I soldered a resistor onto a PCB, it left a stange yellowish-brown coloured stain. Is this normal? I carried out the procedure of soldering properly and i noticed a few of my peers also had the same conclusion. Any help would greatly be appreciated. Is this an issue, if so how do i solve it? Many Thanks, legendary29
Most solder has a core of flux. Flux is a yellowish brown colour. I have soldered millions of things for more than 50 years and I have never removed flux on a pcb.
Since moving away from 60/40 tin lead solders, some flux residue can create problems. Even "no-clean" or the "water soluble" varieties can, and do provide a path for leakage currents... it can cause big problems with instrumentation circuits. It also depends on the environment in which the "device" will be used. I've seen cases where the flux wasn't removed properly and the “device” was potted with a particular potting material and a chemical reaction formed Sulfuric acid and "ate" copper etch and wires. Strange things can also happen in environments where fossil fuels are burned and the byproducts have interactions with the flux.
Yellow Residue?
Posted - Dec 08 2008 : 2:33:48 PM
