Experimental study on uniformity of copper layer with microstructure arrays by electroforming

Metal microstructures have a high potential to meet high application requirement of a variety of new industries because they can make components obtain optical, thermal, bionic, and other functional properties. Electroforming is one of the most efficient technologies for large-scale fabrication of micromachined devices with microstructures due to its good repeatability and reproducibility. However, the thickness nonuniformity of the electroformed layer is a bottleneck problem in the preparation of microstructures, which leads to quality defects such as voids in the microstructures. In order to fabricate the void-free microstructures, pulse electrodeposition of copper was proposed in this paper. The effects of pulse electrodeposition parameters on the surface morphology and thickness uniformity of copper deposits were investigated. In this paper, copper was electrodeposited by direct current and pulse current respectively on the microgroove arrays with an aspect ratio of 2.5:1. The experimental results revealed that the pulse parameters can effectively improve the quality of the electroformed layer and enhance the uniformity of the microgrooves. It was determined that the pulse average current density 2 A/dm², the duty cycle 20%, and the frequency 2000 Hz were the optimum parameters for copper electroforming. Under these conditions, the void-free microstructures were successfully prepared.