Abstract
The layer combination Ni/Pd/Au, also named as ENEPIG (Electroless Nickel, Electroless Palladium, Immersion Gold) is a well-established final finish for high performance and high solder joint reliability in packaging applications. The coating properties are thereby defined by the type of electrolytes which are used for the plating. A specific focus lies on the palladium and gold deposit which play a major role in regards to the final finish reliability. In particular if high thickness of palladium and gold are required, the use of a pure palladium deposit and a gold electrolyte with a partial autocatalytic reaction is highly recommended. The pure palladium plating process as well as the mixed reaction gold plating process are both available in the market for several years already and have found their way into the packaging industry. In this paper a comparison of the different electrolytes for Ni/Pd/Au plating will be given and the performance in regards to solder joint reliability, IMC formation and bonding behavior will be judged. Two new processes for pure palladium plating and mixed reaction gold plating are introduced and compared to the processes which are present in the market. The new processes offer benefits in the efficiency of the plating process, allow to save cost by the reduced precious metal content and provide highest reliability for final finishes in the packaging industry. Data for different plating conditions are presented and the impact of the different conditions such as thickness variation or aging are shown and discussed. With the new types of palladium- and gold- plating electrolytes a new generation of Ni/Pd/Au process can be introduced, which allows the combination of high process robustness, reduced precious metal cost and high final finish reliability in packaging applications.
Published Version
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