METHOD OF FORMING CONVERSION COATING BY USING ACIDIC CONVERSION COATING COMPOSITION

摘要

PURPOSE: A conversion coating forming method is provided to prevent dissolution into inorganic acids by forming an oxide film excellent in acid resistance and bonding strength on a printed circuit board. CONSTITUTION: A method of forming a conversion coating comprises the following steps: A PCB is washed. The PCB is flushed with water. The PCB is pre-dipped into a pre-dip composition for 10secs to 10mins at 10 to 60deg.C. The pre-dip composition consists of 0.1 to 5.0V% sulphuric acid, 0.1 to 10.0V% hydrogen peroxide, and at most 10wt% mixture on the volume basis of the pre-dip composition. The mixture is composed of at least one of a group including sulphur compound; and reaction accelerator and stabilizer. The PCB is dipped into a conversion coating composition for 1 to 6mins at 10 to 60deg.C. The composition consists of 0.1 to 30V% sulphuric acid, 0.1 to 15.0V% hydrogen peroxide, and at most 50wt% mixture on the volume basis of the composition. The mixture is composed of at least one of a group including sulphur compound; and film forming agent, etching rate adjusting agent, reaction accelerator and stabilizer.