Surface treatment chemicals copper plating

Electroless plating. Electroless plating is a siuface treatment process that does not require electric current, as does electrolytic plating. Electroless plating deposits a dissolved metal, such as copper or nickel, on the surface of a plastic part through the use of a chemical solution (Fig. 9.34a). Also, any plastic part to be plated mth the electrolytic process must first be electroless plated to create a conductive surface. 

As with all immersion metal systems, the copper needs to be perfectly clean and textured before the tin plating step. A predip is used to main tain proper chemical balance in the tin bath and prevent contamination. The tin deposition is not a direct galvanic displacement, since tin is more electronegative than copper. Thiourea is used in tin chemical formulation to create a copper-thiourea complex on the surface. This complex becomes more electronegative than tin, and then participates in the immersion reaction. Because of the need to drive the reaction, the tin bath contains relatively high concentrations of chemicals, which must be thoroughly rinsed. Waste treatment of the system is comphcated due to high levels of thiourea. 

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