Dross characteristic

Always experiencing dross in pot with different characteristic such as color, shape, dry/wet etc. Any paper, wetsites provide the more comprehesive explanation on its characteristic

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| Always experiencing dross in pot with different characteristic such as color, shape, dry/wet etc. Any paper, wetsites provide the more comprehesive explanation on its characteristic | Dross is a mixture of various things. The obvious ones are metal oxides admixed with metal and this can vary in colour with temperature and composition - remember some intermetallic oxides can form at lower temperatures than the pure metals. Of course, the main component is tin oxide (black SnO and more commonly white SnO2). On top of this is a host of gunges removed from the PCB, such as flux residues, metallic salts (of all colours), sticky labels, etc., the organics generally becoming rapidly carbonised. There is therefore no "fixed" composition.

The interesting thing about dross is that an absolutely oxide-free solder will not oxidise readily to form a metallic dross but, as soon as there are minute particles of dross in suspension in the solder, these will seed the formation of dross in a big way. This is one very good reason to use a de-oxidised solder such as Vaculoy or Extrusol.

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| Always experiencing dross in pot with different characteristic such as color, shape, dry/wet etc. Any paper, wetsites provide the more comprehesive explanation on its characteristic | "Dross Myth Vesus Fact," R. Woodgate, SMT, 10/98

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