Process for selective deposition of OSP coating on copper, excluding deposition on gold

• Main Author: WENGENROTH KARL F
• Format: Patent
• Language: English
• Published: 25.02.2003
• Edition: 7
• Subjects: CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; CHEMICAL SURFACE TREATMENT; CHEMISTRY; CLADDING OR PLATING BY SOLDERING OR WELDING; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; DIFFUSION TREATMENT OF METALLIC MATERIAL; ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR; ELECTRICITY; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; MACHINE TOOLS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS; METAL-WORKING NOT OTHERWISE PROVIDED FOR; METALLURGY; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLICMATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASSC23 AND AT LEAST ONEPROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25; NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; PERFORMING OPERATIONS; PRINTED CIRCUITS; SOLDERING OR UNSOLDERING; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; TRANSPORTING; WELDING; WORKING BY LASER BEAM

A method is provided for the selective deposition of an organic solderability preservative (OSP) coating on copper surfaces of articles such as electronic components, e.g., printed wiring boards, to serve as a protective coating and preserve the solderability of the copper surface while substantially excluding gold surfaces from attracting the same OSP coating which coating causes cosmetic defects in the form of staining and may reduce the conductivity of the gold contact surface. The method improves the conventional OSP process and utilizes a pre-treatment of the copper surface before applying the OSP coating comprising treating the cleaned and preferably micro-etched copper with an aqueous solution of benzimidazole or derivative thereof to form a precoat on the copper surface. After the pre-treatment step, the precoated copper surface is conventionally treated with a suitable OSP solution such as an aqueous solution of a substituted benzimidazole compound, preferably at the 2-position.