Microstructure and its subsequent evolution of Sn37Pb/Cu column interconnect obtained by friction plunge welding

•Micro-join can also be achieved by friction plunge welding.•Column planting of CuCGA was transformed into a solid-state welding without mold.•A thin, wave-like Sn/Cu diffusion layer formed on solder/Cu column interface.•Grain breakage, plastic flow and dynamic recrystallization occurred in solder zones near interface. To optimize the column planting process of copper column grid array (CuCGA) package, friction plunge welding was proposed to implement the solder/Cu column interconnect assisted without mold. On account of friction and extrusion action during feeding of Cu column, high homologous temperature and large strain, which conformed to the condition of dynamic recrystallization, were generated in the solder zones near interface. The irregular island-like, fragment-like recrystallization α-Pb phases and striped-like α-Pb phases in β-Sn matrix formed at different distances from the interface of Sn37Pb/Cu column, respectively. Meanwhile, a thin, wave-like Sn/Cu diffusion layer formed at the interface. This indicates that micro-join can also be achieved by friction welding method, and the column planting is changed into a solid-state welding from conventional soft soldering. After the subsequent reflow soldering, the diffusion layer transformed into scallop-like, most α-Pb phases in the solder regressed to disk-like, and the pull-out load of joint is not lower than that of traditional column planting method.