Direct Current Electrodeposition of Fe-Ni INVAR Alloy Films and Numerical Simulation of Thickness Uniformity

Abstract Fine Metal Mask (FMM) is an expendable thin film densely covered with arrays of micropores, which is used in the evaporation process of manufacturing OLED. Its material is INVAR alloy (Fe-Ni 36 wt.%) with low coefficient of thermal expansion. When the INVAR alloy film is manufactured by direct current (DC) electrodeposition. Controlling the composition of the electrodeposited layer and ensuring uniform thickness of the deposited layer is a challenge. To solve the above problems, the authors combine experimental and simulation methods. Firstly, orthogonal experiments L16 (44) with four factors and four levels are conducted, which use NiSO4 concentration, current density, pH value, and temperature as influencing factors. Based on the results of the experiment, range analysis demonstrates the consequence of four factors on the Fe content of electroforming films. Then, the electroforming films conforming to INVAR alloy composition are obtained by single-factor experiments. Aiming at the problems of time-consuming and poor universality of traditional experimental methods to solve the problem of uneven thickness of the electroforming layer, a simulation model of INVAR alloy electrodeposition process based on COMSOL is established. The effects of stirring speed and the distance between anode and cathode on thickness uniformity are investigated. Finally, through the reasonable selection of stirring speed and the distance between anode and cathode, the problem of uneven thickness of sediment layer is effectively solved. Electrodeposited layers with uneven thickness of only 7.8% can be obtained by selecting suitable process parameters. The research findings can provide theoretical guidance and technical support for the fabrication of high-resolution and high-precision FMM through electrodeposition.