Effect of dislocation and residual stress on etching performance of 12 μm thick rolled copper foil during pre-stretching

Abstract

With the rapid development of new electronic information industry in 5G era, the development of various electronic components towards high speed and multi-functionality, and higher requirements have been put forward on the precision of circuit boards, the quality and rate of signal transmission. The 12 μm thick rolled copper foil is the thinnest rolled copper foil that can be stably produced, which is essential for the manufacture of high-end Flexible Printed Circuit (FPC) boards. The different microstructure and stress states of 12 μm thick rolled copper foil was obtained through different degrees of pre-stretching. And then the effect of dislocation and residual stress on the etching performance of copper foil was systematically investigated. The results show that the etching rate of copper foil increases and then decreases with the increasing of pre-stretching strain. And the etching rate of copper foil increases rapidly when the pre-stretching strain increases from 0.67% to 0.83%. For the dislocation, the rolled copper foil has higher dislocation density, and the dislocation density gradually increases with the increasing of pre-stretching strain. For the residual stress, the rolled copper foil has higher residual compressive stress. The residual compressive stress decreases and then turns into residual tensile stress with the increasing of pre-stretching strain. The residual compressive stress and dislocation reduce the etching rate of copper foil, and the residual tensile stress increases the etching rate of copper foil within a certain range. The four stages of etching rate variation of copper foil during pre-stretching were clarified, and the calculating model of etching rate was constructed when the dislocation density or residual stress acts as a single factor or dual factors.