THE STUDY OF EFFECTS AND MECHANISMS OF INDUSTRIAL CONTROLLED FACTORS ON ELECTROLESS NICKEL IMMERSION GOLD (ENIG) PLATING PROCESS

Abstract

This research aimed to study the effects of the factors and mechanisms which were controlled by the industry on the electroless nickel immersion gold (ENIG) process including pretreatment step and condition used in ENIG. The thickness analysis of nickel and gold layers by X-ray fluorescence spectrometry (XRF) found that increasing the concentration of precursors, chelating agents, the alkalinity in the controlled range, temperature, and decreasing of oxides on the surface of the substrate resulting in a thick layer of nickel and gold. Also the phosphorus on the nickel substrate caused the thinner layer of gold. For the Ni/P alloy, the nickel composition ratio measured by energy dispersive X-ray spectrometer (EDX) would be greater due to increasing of nickel salt, alkalinity in the EN plating solution or temperature. However, increasing the temperature more than 90 oC caused decomposition of EN plating solution. Moreover, the decreasing of reducing agent resulted in increasing of nickel composition ratio of nickel alloy. The factors affected the roughness and morphology of the nickel surface measured by scanning electron microscopy (SEM) and stylus containing the morphology of the substrate, the gas bubbles generated by the plating reaction which affected the flow of the plating solution and agitation. In the case of gold roughness was based on the nickel surface roughness. The too thick gold plating layer resulted in the dropping of the adhesion between gold layer and nickel surface. The sensitive parameters of EN plating were by-product of plating reaction and pH of EN solution. For IM plating, the sensitive parameter was pH of IM plating solution.