Calculation Study On The Properties Of Compounds In Sn Solder

Sn solder is currently the most widely used packaging material in the electronic packaging industry and has a significant impact on the performance of electronic products.Compounds are widely present in Sn solders and brazing joints,and can play a role in improving the performance of solders and increasing the strength of joints.Due to the difficulty of preparing pure compound single crystal samples and the difficulty of accurate measurement due to performance anisotropy,most of them lack accurate performance data,which hinders the design and development of solders.The current research and development mode of solder mainly relies on the researcher’s personal experience and a large number of repetitive experiments.This method has high cost,poor accuracy,and long development cycle.Drawing lessons from the "Materials Genome Initiative",using a combination of material calculations and experiments,theoretical calculations and verifications of compound properties are carried out.This work is of great significance for the accumulation of basic data of solders,optimizing solder design,and improving joint performance.Using the first-principles calculation method based on density functional theory,the Sn solder and the metal element and compound in the connection interface are the research objects,and the performance theoretical calculation research is carried out.Establish the relative relationship between the structural stability of the compound and the alloying ability,establish the relationship between the elementary substance and the electrode potential of the compound,and obtain the mechanical and thermodynamic performance parameters of the elemental metal and the compound.The results show that the calculated value is more consistent with the experimental value,and some performance parameters that are difficult to obtain in the experiment have been obtained.The main conclusions are as follows:Among the binary Sn solders,Cu6Sn5 has the best stability,and AuSn has the strongest alloying ability and is the first to be formed in the solder;among the multi-component Sn solders,CoSn has the best stability and Ni3Sn2 has the strongest alloying ability and is the first to be formed;FeSn has the best structural stability in the interface,and AuSn4 has the strongest alloying ability and is formed first in the connection interface.With the increase of Sn content,the structural stability of Co-Sn and Ni-Sn compounds decreases,and the alloying ability of Co-Sn compounds decreases.With the increase of Zn content,the structural stability and alloying ability of Ag-Zn and Cu-Zn compounds decrease,the more difficult to generate.The AgZn3 supercell model is constructed,and the mechanical properties of the element and compound are calculated.Zn,CoSn and FeSn2 are brittle materials,and other simple substances and compounds are plastic materials;AuSn,AuSn2 and CuZn have strong elastic anisotropy,which can easily induce microcracks and reduce the mechanical strength of the solder.With the increase of Sn content,the bulk modulus,shear modulus,Young’s modulus and hardness of Co-Sn and Ni-Sn compounds decrease,the elastoplasticity of Co-Sn compound increases,and the elastic anisotropy of Ni-Sn compound increases;As the content of Zn increases,the bulk modulus and elastic anisotropy of Ag-Zn compounds decrease;Ag-Zn and Cu-Zn compounds with the same crystal structure have higher structural stability,alloying ability and bulk modulus than Cu-Zn compounds Ag-Zn compound.The electronic density of states of element and compound are calculated,both of which have good metallicity and conductivity;Ni,Co,FeSn and FeSn2 are ferromagnetic materials,and Co-Sn and Ni-Sn compounds are paramagnetic materials;Fermi level is calculated to obtain the electrode potential sequence,which can be used to determine the electrochemical corrosion of Sn solder and joints.The thermodynamic properties are calculated and are consistent with the performance trends obtained in the thermodynamic handbook.Ag and Au,Ag5Zn8 and Cu5Zn8,Al2Cu and FeSn2 have similar thermodynamic properties.The thermodynamic properties of AuSn and CuZn are little affected by temperature;as the temperature rises,the isothermal specific heat tends to be a constant related to the lattice structure.The physical properties of the compounds in the Sn solder are calculated theoretically through the first-principles calculation method,and the theoretical calculation results obtained are similar to the experimental data,which can provide theoretical data and basis for solder design and promote the development of solder digital design technology.