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Presence of Copper

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Presence of Copper | 9 October, 2012

Put on your Chemical Thinking Caps.....

We are ablating the mask of a PCB which was over a copper layer. This exposes copper.

Outside of an electrical test (no can do) how could we use a fast non-destructive test in order to determine that copper (an not a minuscle layer of mask on top) is exposed. We have to run through 50K boards and will be using a sampling plan.



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Presence of Copper | 9 October, 2012

Hi Bob

Ideas to consider are: * Use your handheld XRF * Swab vinegar on the copper and watch it brighten * Use the following procedure

Nearly all copper minerals can be dissolved by melting with a mixture 1:2.5 of ammonium chloride and ammonium nitrate on a magnesia furrow. This melt is dissolved in a rather concentrated solution of ammonium carbonate, a deep blue colour indicates the presence of copper. Even small amounts are detected in this way if the solution is transferred to a small test tube; by looking in the axial direction from top to bottom the colour perception is independent of the height of the solution column. Identification is impaired by the presence of Ni, because Ni also causes a light-blue coloured solution with ammonium carbonate. To avoid any uncertainty some of the blue solution is brought to an acid reaction by acetic acid, and a solution of potassium ferrocyanide K4Fe(CN)6 is added. A brown precipitate indicates the presence of copper. Zinc ferrocyanide paper may be used instead. It should be mentioned that many secondary copper minerals are soluble in ammonium carbonate solution, e.g. malachite, azurite, all basic sulphates, phosphates, chlorides, and the copper silicates chrysokolla and dioptase. The dissolution rate of Cu-silicates is enhanced by the addition of ammonia solution. [Quick assays in mineral identification: A guide to experiments for mineral collectors and geoscientists in field work, Walter A. Franke, retired Professor of Mineralogy, Freie Universität Berlin, Germany]

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Presence of Copper | 10 October, 2012

"a brown precipitate" Now that's a term I understand.

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Presence of Copper | 10 October, 2012

a brown precipitate is something you get after eating a beefy bean burrito.

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Presence of Copper | 11 October, 2012

Remember when the whole 'lead-free' thing first hit us in the stomach? Companies were selling swabs that could detect the presence of lead, which we purchased in hopes of determining if the solderability protection on components was not leaded.

I did a quick google search, but couldn't anything like that for detecting copper. It seems like there should be.

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