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PCB007-Oct2020

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50 PCB007 MAGAZINE I OCTOBER 2020 Electrodeposition can be traced back to the 1800s. Plating decorative gold on a silver sur- face using a voltaic cell was exciting at that time. Along with electrodeposition, surface prep or pretreatment was an integral part of the process. Pretreatment is usually customized to the incoming substrate and the plated metal. It is designed to clean organic and inorganic con- taminants from the surface. In addition, pre- treatment may alter the surface morphology of the substrate for adhesion enhancement. It is a critical step and must be completed be- fore plating to achieve the desired adhesion and to enhance the quality of the deposited metal. Pretreatment utilizes cleaners and etching steps. In some applications, pretreatment is used to modify the substrate to allow plating to initiate. Chemistries used in pretreatment are not compatible with the plating process and must be thoroughly rinsed before plating. Rinsing for electronic manufacturing is usual- ly done in a two- or three-step cascading flow- ing rinse. The following is a description of the desired pretreatment for the following applications: 1. General metal finishing 2. Plating for electronics manufacturing: • Electroless copper plating • Acid copper plating • Surface finish 1. General Metal Finishing Metal surfaces must be pretreated before plating. The objective is to remove contami- nants from the surface. Contaminants may be organic (oils, grease, fingerprints) or inorganic (scale, stains, and oxides). The Critical Role of Pretreatment for Plating The Plating Forum by George Milad, UYEMURA

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