For the infrared imaging system,reducing the pixel pitch is one of the important developments topics at present.In order to achieve a small pixel pitch,one of the keys is to prepare small indium bumps with high precision and homogeneity.In this paper,through a series of experiments and analysis for 7.5μmpixel pitch,the effect of different combinations of Under Bump Metal (UBM)and the indium column size on the preparation of In bumps is studied,which provides good guidance for the preparation of high precision small In bump arrays.