Effect of Metal Finishing Wastes on Sewage Purification

The through-hole plating of printed circuits is essentially a method of electroplating non-conductors, and can be divided into four basic sections—cleaning, activation, metallization and electroplating. Activation consists of the absorption of tin compounds and a precious metal from either two separate solutions or one single solution; a comparison is drawn between these two methods indicating the advantages to be gained from the single stage solution. Electroless copper solutions are generally used for metallization and the working parameters of these are considered. Build up of the electroless film is carried out in copper electroplating solutions of which several types are available. A comparison is drawn between these solutions, with respect to throwing power, stability and grain structure of the deposit. Other electroplating systems used to deposit etch resists and solderable surfaces are also discussed.