Oxidation when soldering

Discussion in 'General Electronics Chat' started by Dritech, Jul 16, 2016.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    Hi all,

    I am doing some experiments to check the effect on resistance after the soldering process.
    Does oxidation happen instantly after soldering? what methods can be applied to prevent oxidation after soldering? (withough applying any protective spray or something of that sort)
  2. dl324

    Distinguished Member

    Mar 30, 2015
    Oxidation will begin immediately after soldering. Metals used in typical solders aren't prone to excessive oxidation; that's why copper wires are often "tinned" with solder.
  3. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    Store the soldered item in an oxygen-free environment.
  4. Tonyr1084

    Well-Known Member

    Sep 24, 2015
    Free oxygen? All the oxygen you can breathe for free?

    Sorry Blocco, just had to pierce in and be silly.

    Oxidation is the worst during soldering IF no flux is used. Nearly all solders have a flux core of some sort. Some are "No Clean", others are "Water Soluble" to name a few. "Rosin Core" is another, but this one you want to clean with some sort of flux cleaner. Depending on the exact chemistry of the flux it can be anywhere from very mildly corrosive to rather aggressive. And if you fail to clean it off it can deteriorate your work.

    When you heat and reheat solder it dries out (so to say) and can appear as if it were a cold solder joint. That's because without flux oxygen begins to oxidize the surface (where oxygen contacts the molten solder) forming solder dross. Dross is the unwanted byproduct of hot solder. The purpose of flux is to replace the oxygen in the immediate location where the solder is being applied so it doesn't oxidize. It has other purposes as well, such as cleaning the surface of the copper pad to aid in solder wetting (adhesion of the solder to the copper).

    As for storage of electronics - which the computer you're working from right now - has solder joints that were made some time ago. So no real application is necessary to prevent oxidation. However, an unprotected copper trace can become oxidized rather quickly if it comes in contact with something like the oils found on the human hand. It can tarnish - or if worse, it can corrode its way through the traces. For many years electronics were built without the aid of solder mask and conformal coating.

    Solder mask is a protective coating on the board meant to protect all the areas of the copper traces that solder is not intended to be applied to. Conformal Coating is a clear coating (spray type is most common and is applied after the board is complete) is meant to protect the board from moisture. Some conformal coatings are very good at sealing a board and in such cases the board can be submerged in water and not suffer any ill effects from contact with moisture.

    As for concerns over oxidation during storage - I wouldn't worry about it.
  5. SLK001

    Senior Member

    Nov 29, 2011
    If your joint is oxygen free (meaning that you did it properly), then the effects of the surface oxidation will not be detectable in your measurements.