Constant-temperature precipitation for regulating the content of Tin–Copper alloy elements - research on a new filter screen filtration process and the precipitation mechanism of Cu6Sn5

During the hot-dip tin plating process, copper content in the tin bath rises as copper sheets and strips are immersed, affecting plating quality. Current methods for regulating tin and copper elements demand highly specialized equipment. Therefore, exploring simple and environmentally friendly regulation processes is essential. This study leverages the thermodynamic similarity between Sn and Cu to investigate the precipitation mechanism of Cu 6 Sn 5 within a temperature range of 250 °C to 350 °C and a holding time of 10 to 60 minutes. The precipitated Cu 6 Sn 5 is collected on a filter screen to form residue through filtration. Areas with lower copper content in the sample melt first and pass through the filter screen, becoming recyclables and reducing copper content. Optimal performance was achieved at 260 °C for 40 minutes, with residue and recycled materials comprising 35.86 wt.% and 64.14 wt.%, respectively. Recovery rates for tin and copper were 64.79% and 66.83%. The copper content in recycled materials decreased from 2.07 wt.% to 1.07 wt.%. The precipitation of Cu 6 Sn 5 progresses through three distinct stages: growth, coalescence, and morphological transformation, with its content gradually increasing throughout these stages. Cu 6 Sn 5 has a dominant growth direction along the <0001> during the morphological transformation stage, and the growth rate along the <0001> is significantly greater than that along the width. The area ratio of Cu 6 Sn 5 increases from 7.92% to 14.65% as the grains fuse, while the number of grains decreases. In contrast to existing methods that necessitate vacuum, high temperature, or supergravity conditions, this process requires only atmospheric pressure heating and filtration. It offers notable advantages in terms of equipment simplicity, energy consumption, and processing time, thereby presenting a green, straightforward, and rapid approach for regulating the content of tin-based tin-copper alloy elements.