Through-mask electrochemical machining of hole arrays on molybdenum sheets

Abstract

Molybdenum is an important modern industrial material. It is widely used in high-energy and high-heat environments due to its high melting point and thermal conductivity, as well as its low thermal expansion coefficient. Hole arrays on molybdenum sheets are commonly used in industry, with applications in ion plating equipment, projection electron microscopes, cryo-electron microscopy, and electron guns. However, fabrication of these arrays on molybdenum sheets is very difficult due to high opening ratio limitations, deformation of thin sheets, and the mechanical properties of the metal. Therefore, high-efficiency, high-precision fabrication of hole arrays on molybdenum sheets has emerged as a focus of research. Through-mask electrochemical machining (TMECM) is an effective method of fabricating hole-type components. This paper describes a method of fabricating hole arrays on a sheet using a TMECM process in a neutral NaNO₃ solution. Polarization and current efficiency curves were measured for molybdenum in a NaNO₃ solution to identify its electrochemical characteristics in the electrolyte. The results show that molybdenum dissolves well in NaNO₃ solutions and exhibits good surface erosion uniformity. Furthermore, it does not produce obvious protuberances, dimples, or stress cracks. The experimental results indicate that hole arrays can be fabricated on molybdenum sheets with relatively high precision via a TMECM process with appropriate processing parameters. The aperture deviation was less than 0.05 mm, and the roundness deviation of the holes was less than 9.8 μm.