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Copper oxide

yngwie

#25320

Copper oxide | 31 July, 2003

I faced problem over connecter's pin that were hot air soldered. This connector has 168 pins ( similar to the straddle connector ). The process is to apply the flux onto the connector's J-leads, and the hot air pencil were then ran thru' the leads to melt the pre-deposited solder ( attached to the connector ). Solder joints were perfect but there was a greenish colour residue built up after a few days on the unsoldered leads near the body. I suspect this came from the high soldering hot air temperature setting. I think this it is the copper oxided ( base matreial for the connectors are copper ). I'm not sure, when my customer told me that this could be a corrosion. Could any of you guys tell me what exactly is this greenish thing ? The flux we use is NR330 no clean.

Inputs are welcome.

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#25325

Copper oxide | 31 July, 2003

Q: Could any of you guys tell me what exactly is this greenish thing ? A: No, but is not copper oxide. Copper oxide is brown, the color of a penny [here in the US] or an untreated copper laminated trace on a board. Many copper salts are greenish in color (especially in the presence of water). It could be copper sulfate, copper nitrate or copper chloride. A chemical analysis can show what salt is on the pins.

So, aside from being green, what is the texture [ie, smooth, glossy, crusty, etc] of this residue?

This residue could be from: * Residual materials on the connector as it came from your supplier. * Using flux other than the expected NR330 no clean * Appling the expected NR330 no clean flux with a snow shovel.

Returning to the identification of this green residue issue, corrosion-doctors.org say, 1a Pretty Patina * Copper Oxide, Cupric Oxide, Cuprous Oxide: (red, brown or black). Cuprous oxide is generally reddish in color and tends to form first. It quickly converts to cupric oxide which is dark brown or black in color. Virtually all ancient bronze coins have at least a thin layer of brown copper oxide directly on the metal surface. * Copper Sulfate or Sulfide (green to black) * Copper Carbonate (accounts for most green patina and occasional blue). Copper carbonate is a reaction to copper oxide, not to copper, so it will only form on top of the brown or red copper oxides. Because copper oxide is more stable than copper carbonate, the green can sometimes be selectively removed leaving the red or brown. * Copper Acetate (green, occurs frequently with copper carbonate) 1b Destructive Patina * Cuprous Chloride and Cupric Chloride (pale green powdery spots on the surface of a coin or artifact). While there are generally a number of reactions occurring on the surface of a coin at any given time, the presence of chloride ions is the most destructive, since they produce hydrochloric acids which eat your coin thus producing more Cuprous Chlorides to... etc. until there is no artifact. * Reddish Warts - we are not sure what this is, but its bad. This is scaly bumps usually 3-7mm high that form on the metal. It can be removed but is extremely destructive, leaving large pits and destroying most details. Bronze that shows this type of degradation is frequently unstable and soft even in the areas not directly affected by the warty encrustations themselves. I personally will not buy pieces with this symptom as they tend to look bad and do not respond well to cleaning.

As an arguably logical extension, for discussion on the causes of the color on archaeological bronzes: http://www.cci-icc.gc.ca/whats-new/news21/bronze_e.shtml

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Yngwie

#25335

Copper oxide | 1 August, 2003

Thanks Dave, the residue appeared to be similar to fungus. First, I thought it could come from water soluble flux but, our plant only runs no-clean. So, can I concluded that this greenish "fungus" looking staff is not initiated from high hot air temperature setting ?

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#25338

Copper oxide | 2 August, 2003

Q: So, can I concluded that this greenish "fungus" looking staff is not initiated from high hot air temperature setting ? A: Your temperature setting could have increased the growth rate of this crunchy looking stuff, but we wouldn't start there to find it's genesis.

Places we'd start are: * Residual materials on the connector as it came from your supplier. * Using flux other than the expected NR330 no clean * Appling the expected NR330 no clean flux with a snow shovel.

Performing a chemical analysis to show what salt is on the pins could be useful.

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