With the progress of science and technology, an increasing number of peritectic alloys, such as Fe-Cr-Ni, Ti-Al, and Nd-Fe-B alloys and Cu-Sn alloys for eletronic packaging, are being widely used in industrial production fields because of their excellent properties. With the development of the electronic information industry towards miniaturization and multifunctionality, higher requirements are put forward for the mechanical, electronic and thermal properties of integrated circuits. In this paper, Cu-50 at. %Sn peritectic alloy (L+Cu 3 Sn→Cu 6 Sn 5 ) was used as the research object. The Bridgman directional solidification method was used to observe and measure the microstructure under a microscope. When the growth distance and temperature gradient are constant, with increasing growth rate, the primary phase Cu 3 Sn undergoes a transformation from a cellular → cellular/dendritic → dendritic structure, and the size and spacing of the Cu 3 Sn phase decrease. When the growth rate and growth distance are constant, the primary phase Cu 3 Sn changes from a block and dendrite to a cellular structure with increasing temperature gradient. When the growth rate and temperature gradient are constant, with increasing growth distance, the primary phase Cu 3 Sn changes from block and cell/dendritic to cellular structure, and the size of the Cu 3 Sn phase is slightly refined. Based on the above experimental results, a diagram of the microstructure under different growth rates, temperature gradients and growth distances was drawn, and the influence of the

solidification conditions on the microstructure of the Cu-50 at. %Sn peritectic alloy are further clarified.