Fabrication of thin copper mesh for electromagnetic interference of display panel by pulse reverse current method and study on the microstructure by small angle neutron scattering

Abstract

A copper sheet with mesh was mass-produced by continuously combining three techniques, electroforming with pulse-reverse current, transfer technique onto a transparent polyimide (PI) film and oxidation processes. Thiourea as an organic additive in a modified copper sulfate bath changes the reduction potentials of copper complexes, which results in effectively controlling the crystal orientation, surface roughness and microstructure of the copper layer. An electroformed copper layer without thiourea has a relatively rough surface with an average surface roughness of about 144.7 nm, whereas, the copper layers with thiourea have a smooth surface with an average surface roughness in the range of 6.3 to 12.1 nm. The copper layers with thiourea have a preferred orientation of crystal structure such that Cu (111) peak intensity increases, whereas, Cu(220) peak intensity decreases with thiourea addition. Electroforming with a rectangular pulse current density including etching at +640 mAcm−2 for 1.8 msec and plating at −160 mAcm−2 for 4 msec in a modified copper sulfate bath with 200 ppm-thiourea at 25 °C is one of optimum conditions to massproduce a copper mesh sheet roll with 300 μm pitch, 10 μm mesh width and thickness, and 200 m long.