Study on Improvement of Solder Bonding Characteristics and Analysis of Improved Mechanism using New Electroless Thin Ni/Au Plating Process

Abstract

Fine pattern formation (L/S＝less than 50 μm) using electroless nickel/gold plating, extraneous nickel deposition on the resin area of a fine pattern is often observed because of residual palladium catalyst on the patterns. Thinner nickel plating was applied to solve the problem. However, a tendency for local nickel corrosion caused by the immersion gold plating step increases. Also, the solder connection reliability decreases compared to conventional nickel/gold processing. Accordingly, this study investigated the influence of palladium catalyst deposition conditions on electroless nickel/gold plated film properties. We propose direct electroless nickel strike plating on copper patterns without the palladium catalyst. Generally, solder bonding strength with electroless thin nickel /gold plating decreased concomitantly with increased palladium catalyst treatment time. In contrast, the nickel strike plating time does not influence solder bonding strength. Uniform nickel deposition and good solder bonding strength were achieved by applying the electroless nickel strike plating method.