Preliminary Step in Formulating the Optimum Electroless Nickel Bath Using Taguchi Method

Abstract

Teknologi penyaduran nikel secara tanpa elektrik telah berkembang pesat dan diaplikasikan secara meluas dalam banyak bidang industri disebabkan ciri sadurannya yang unggul. Penyaduran tanpa elektrik ialah suatu proses pengautomangkinan iaitu saduran nikel berlaku daripada penurunan garamnya oleh agen penurunan yang hadir dalam larutan elektrik. Komposisi asas larutan tanpa elektrik di dalam kajian ialah NiSO₄.6H₂O, NaH₂PO₂.H₂O, (NH₄)₃C₆H₅O₇, agen pembasah dan suhu operasinya ialah 50°C. Dalam kajian awal ini, teknik Taguchi telah digunakan untuk menyelidik beberapa faktor yang dapat mempengaruhi kadar saduran supaya larutan elektrolit nikel yang optimum dapat diformulasikan. Faktor-faktor ini ialah kepekatan garam nikel, agen penurunan, agen pengkompleks dan pH larutan. Susunatur ortogonal Taguchi L₉ telah digunakan untuk merancang eksperimen dengan tiga paras bagi setiap faktor. Kepingan keluli lembut digunakan sebagai substrat. Proses penyaduran dijalankan selama setengah jam dan kadar saduran didapati dengan menimbang sampel sebelum dan selepas saduran. Data-data yang diperolehi telah dianalisis berdasarkan nisbah isyarat kepada bisingan Taguchi dan analisis varians. Keputusan menunjukkan bahawa faktor pH paling mempengaruhi kadar saduran diikuti dengan faktor kepekatan garam nikel, agen penurunan dan agen pengkompleks. Formulasi larutan elektrolis yang optimum seterusnya dapat diramalkan berdasarkan keputusan ini. Kata kunci: Penyaduran nikel secara tanpa elektrik; kaedah Taguchi; susun atur ortogonal Taguchi; kadar saduran; larutan tanpa elektrik yang optimum Electroless nickel plating has been rapidly developed and widely used in many fields due to its superior properties of coating. It is an autocatalytic process in which the deposited nickel is reduced from its ionic state by chemical reducing agent in bath. The basic compositions of the bath and operating condition are NiSo₄.6H₂O, NaH₂PO₂.H₂O,(NH₄)₃C₆H₅O₇, wetting agent and at 50°C. In this preliminary study, Taguchi Robust Design Technique was used to rank several factors that may affect the deposition rate in order to formulate the optimum electroless nickel bath. They were concentration of nickel salt, reducing agent, complexing agent and pH of the bath. The Taguchi orthogonal array L₉ was used for the experimental design with three levels of consideration for each factor. Mild steel plated were used as substrates. The deposition process was carried out for half an hour and the rates were obtained by weighing the samples before and after plating. The response (deposition rate) was analysed based on the Taguchis signal-to-noise ratio (S/N) and analysis of variance (ANOVA). The results showed that the most notable factor influencing the deposition rate was the pH, followed by the concentration of nickel salt, reducing agent and complexing agent. The optimum bath formulation was then predicted based on these results. Key words: Electroless nickel plating; Taguchi's method; Taguchi orthogonal array; deposition rate; optimum bath formulation