Abstract
In this paper a low temperature metallization i.e. standardization of electroless Ni plating on alumina ceramic is summarized. It includes three main steps (i) pre-treatment, (ii) activation and (iii) Ni plating. Pre-treatment includes degreasing with non-silicate soap solution followed by ultrasonic cleaning in acetone and etching the alumina surface to generate roughness for making it suitable for adhesion. Etching has been obtained by immersion in 10% NaOH at 50℃ for 10 minutes and 50% HF for 15 minutes at room temperature. Activation of the surface is the most important step before electroless plating on alumina ceramic. Activation has been achieved with Ginplate 442 (commercial chemical) by immersing the alumina specimen for 5 minutes at room temperature. Activated alumina samples have been used for electroless Ni plating in Ginplate 418 bath at 88°C.Uniform, densely compact coating has been achieved as revealed by SEM image. XRD plot confirms the presence of metallic nickel together with phases of Ni2P, NiP, Ni3P confirming the nickel phosphite based plating. Subsequently, tube to tube joining of these metallized alumina ceramic tubes has been conducted through vacuum brazing process with copper silver eutectic alloy (28Cu-72Ag) whose cross section showed good joint with excellent wettability of Cu-Ag with Ni plating.
Highlights
E HF for 15 minutes at room temperature
Activated alumina samples have been used for electroless important applications, including those in petrochemical, Ni plating in Ginplate 418 bath at 88°C.Uniform, densely chemical application, ceramic plastics, optics purpose, compact coating has been achieved as revealed by SEM image
Etching of the specimen by 10% NaOH and 50%HF generated rough surface and making it suitable for adhesion of the ions and developing active sites. These etched specimens were further exposed to Ginplate 442 activator where stannous and palladium salts may form a layer so that metallisation process is initiated to promote the formation of the electroless deposits with good conductivity (Fig 2). These electroless Ni plated alumina ceramic tubes were joined through brazing in vacuum furnace
Summary
Commercial chemicals Ginplate 442 [24] solution was used as an activator for activating the surface. It is an acid activator used to prepare the surface before plating for promoting uniform and adherent formation of electroless coating. Activator solution was prepared by mixing 12.5% Ginplate 442 and 12.5% conc. Pre-treated Alumina specimens were immersed in above activating solution for 5 minutes at room temperature (RT)
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