Copper dissolution-migration

Copper, however, is used in applications where purity is important. Copper, when pure, is ductile and an excellent electrical conductor, so it needs to be refined to be used in electrical wiring. Copper anodes (blister copper) are suspended in a water solution containing sulfuric acid and copper sulfate with steel cathodes. Electrolysis results in dissolution of copper from the anode and migration of copper ions to the cathode, where purified metal is deposited. The result is copper of 99.9 percent purity. A similar procedure may be used in recycling copper. Other metals that are electrorefined include aluminum. 

Schaefer s method was improved, taking into consideration the dissolution of the q-layer into the molten solder until the copper concentration in the solder reaches the saturation limit, as well as the additional growth due to the reprecipitation of Cu as Tj after the Cu reaches it saturation limit (Ref 7). In consideration of Cu dissolution into the molten solder to reach the Cu solubility limit, they assumed that Cu dissolution into the molten solder is entirely from the dissolved q IMC. They also assumed that during cooling from the reflow temperature, Cu becomes incrementally supersaturated. The excess Cu atoms in the solder react with readily available Sn to form ri in the bulk solder, or migrate to the interface and precipitate on the interfacial rj layer. The portion that precipitated at the interface is calculated based on the growth controlled by diffusion, and the diffusion coefficient of Cu in liquid Sn was used (Ref 56). 

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