Effect of pH on electroless nickel deposition on alumina substrates for chip resistor application
Alumina has been used widely in electronics industry specifically for chip resistor application. Currently, the deposition of nickel on alumina surface using electrodeposition method suffered from the insufficient bonding between the metallic coating (nickel) and the ceramic substrate (alumina). Electroless deposition method however can produce strong adhesion between the metallic coating and ceramic substrate. In this research, the effect of pH on the electroless nickel on alumina substrate was investigated. The electroless deposition of nickel on alumina substrate was conducted at pH 4.0, 5.6 and pH 10.0 for 3, 5, 10, 20 and 30 minutes at constant temperature. The crystal structure of the substrate and coating was characterized by using X-ray diffraction (XRD). The surface morphology of the coating was observed by using scanning electron microscopy (SEM) and the coating thickness was measure by X-ray fluorescence (XRF). The coating performance was tested by using Standard ASTM D3359 (Tape-Test). It was found that the optimum pH of plating solution was 10.0 with the maximum thickness was obtained at 30 minutes of deposition with thickness of 1.15 μm. These optimum coating parameters shows homogeneous and uniform nickel deposition on the alumina surface as observed by SEM. Nickel deposition by electroless method at pH 4.0, 5.6, and 10.0 have excellent bonding with alumina substrate as shown by tape test analysis.
Electroless alloy/composite coatings: A review
Since the inception of electroless coating by Brenner & Riddell in 1946, it has been the subject of research interest and, in the past two decades, emphasis has shifted to the studies of its properties and applications. The co-deposition of paniculate matter or substance within the growing film has led to a new generation of electroless composite coatings, many of which possess excellent wear and corrosion resistance. This valuable process can coat not only electrically conductive materials including graphite but also fabrics, insulators like plastics, rubber etc. The low coating rates with these can provide better reflectivity of plated surfaces and many more applications. Coatings can be tailored for desired properties by selecting the composition of the coating alloy/composite/metallic to suit specific requirements. The market for these coatings is expanding fast as the potential applications are on the rise. In the present article, an attempt has been made to review different electroless alloy/composite coatings with respect to bath types and their composition, properties and applications. Different characterisation studies have been conducted on various electroless nickel-based coatings with emphasis on wear and corrosion properties.
Relationships among crystallographic structure, mechanical properties and tribological behaviour of electroless Ni–P(9%)/B4C films
Abstract The tribological behaviour of electroless Ni–P composite coatings was investigated by dry sliding tests with a slider-on-cylinder tribometer. The tests were carried out in laboratory air at room temperature against a PVD-TiN coated HSS cylinder. Friction and wear data are discussed on the basis of the mechanical properties (microhardness, plasticity parameter, fracture toughness) of the coatings, that were derived by indentation measurements at low loads. The wear depths measured on unreinforced Ni–P were about one order of magnitude larger than those obtained on the corresponding composite coatings. Furthermore, wear depth proved to increase with increasing annealing time, for both pure matrix and composite layers. The wear volume Q was correlated to the mechanical properties using Archard-type equations. For composite coatings the plasticity parameter δ H was inserted into the equation for the estimation of Q , in order to take into the account the action of a B 4 C-rich layer observed on the surface of the worn coatings.