Effects Of Trace Elements On Properties Of Copper Based Bonding Wire From First-principles Calculations

With the upgrade of semiconductor packaging technology and the development of new electronic industry,the key basic materials of bonding wire are proposed to have finer wire diameter,higher strength and lower cost,and the lead arc is more stable during the bonding process.As one of the new bonding wire materials,copper wire has better electrical and thermal conductivity than traditional gold wire,and the price is much lower than that of gold wire.Therefore,copper wire,a new type of bonding wire material that replaces gold wire,has become a research hotspot and has gradually occupied the market.Researchers have studied the effects of some elements doped into Cu matrix on their mechanical properties and electrical conductivity through a large number of experiments.A number of copper alloy distribution ratios with better comprehensive properties have been determined,but they cost a lot of money and time.At the same time,subject to experimental conditions,the interpretation of the theoretical mechanism has yet to be added.With the rapid development of computer science,theoretical prediction of computational simulation has become an effective research method,so that theoretical guidance experiments can greatly reduce the amount of experimentation.Therefore,this thesis studied 14 different X?Ag?Ni?Zr?Si?Mn?Zn?Mg?Cr?Sn?Fe?P?Be?Al?Ti?doping on the crystal structure,thermodynamic properties,mechanical properties,optical properties and electrical conductivity of Cu were studied,which provided theoretical support for the alloying design of copper-based bond wires,shortening the development cycle and reducing costs.Firstly,the Cu₁₀₇X alloy model with Cu₁₀₈08 and X content of 0.926at%was constructed.The crystal structure of Cu₁₀₈ and Cu₁₀₇X was geometrically optimized.The effect of X element doping on the thermodynamic stability of Cu was studied.The results show that the calculated lattice constant of Cu₁₀₈ is 3.6364?,which is only 0.8%compared with the experimental value.Except Cu₁₀₇Ni and Cu₁₀₇Si,the other Cu₁₀₇X alloys are increased.The Cu₁₀₇Zr alloy has a maximum lattice constant of 3.6480?,and the Cu₁₀₇Si alloy has a minimum lattice constant of 3.5438?;the formation enthalpy of Cu₁₀₇Mn,C₁₀₇Zn,Cu₁₀₇Be and Cu₁₀₇Al is negative,which is easier to form than Cu₁₀₈.The formation enthalpy of Cu₁₀₇Mn is-0.88×10^-2eV/atom,which is the easiest to form.The formation enthalpy of other Cu₁₀₇X alloys is not as positive as Cu₁₀₈,the formation enthalpy of Cu₁₀₇Si is up to 3.03×10^-2eV/atom;the binding energy of Cu₁₀₈ and Cu₁₀₇X alloys are all negative,indicating that they all have thermodynamically stable structure;from the electronic structure,both Cu₁₀₈and Cu₁₀₇X alloys have metallic properties.The covalent bond between Si and Cu atoms is relatively weak,and the thermodynamic stability is also the worst.Then,the elastic constants of Cu₁₀₈ and Cu₁₀₇X alloys were calculated,and the moduli,shear modulus and Young's modulus were derived.The effects of X-doping on Cu hardness and ductility were analyzed.The results show that:The calculated values of the elastic constants of Cu₁₀₇X alloys all satisfy the stability of Born mechanical stability.Therefore,they all have mechanically stable structures.The doping of X elements increases the hardness of Cu to different extents.The intrinsic hardness of Cu₁₀₇X alloys is ranked as Cu₁₀₇Si>Cu₁₀₇Zn>Cu₁₀₇Mg>Cu₁₀₇Be>Cu₁₀₇Ag>Cu₁₀₇Al>Cu₁₀₇Ni>Cu₁₀₇Sn>Cu₁₀₇Ti>Cu₁₀₇Mn>Cu₁₀₇Fe>Cu₁₀₇Cr>Cu₁₀₇P>Cu₁₀₇Cr,the intrinsic hardness of Cu₁₀₇Si and Cu₁₀₇Zn is6.18 and 5.97GPa,respectively.The B/G value of Cu₁₀₇X alloy is more than 1.75 between2.49 and 3.1,and Poisson's ratio?is between 0.323 and 0.355 more than 0.3,therefore,Cu₁₀₇X alloys all exhibit plasticity,and the B/G values and Poisson's ratio?of Cu₁₀₇Cr are higher than 3.0 and 0.35,respectively,and have good plasticity.Finally,the optical properties?reflectance,absorption coefficient,refractive index and dielectric constant?of some static structures of Cu₁₀₈ and Cu₁₀₇X alloys after kinetic relaxation were calculated,and the conductivity of Cu₁₀₈ and Cu₁₀₇X alloys was calculated by Kubo-Greenwood formula.The effects of X-doping on the optical and electrical properties of Cu₁₀₈ and Cu₁₀₇X alloys were predicted.The results show that the optical properties of Cu₁₀₈ and Cu₁₀₇X alloys are high reflection and strong absorption.The optical properties of Cu₁₀₇Zn and Cu₁₀₇Ni are the closest to Cu₁₀₈,and the optical properties of all doped alloys are the best,not only strong.Reflectivity,also has a higher static dielectric constant and refractive index,while the optical properties of Cu₁₀₇Al and Cu₁₀₇Sn are relatively poor;the calculated conductivity of Cu₁₀₈ is 5.39*10⁷S/m.The order of conductivity of Cu₁₀₈ and Cu₁₀₇X alloys is:Cu₁₀₈>Cu₁₀₇Zn>Cu₁₀₇Ni>Cu₁₀₇Fe>Cu₁₀₇Mg>Cu₁₀₇Be>Cu₁₀₇Ag>Cu₁₀₇Mn>Cu₁₀₇Zr>Cu₁₀₇Cr>Cu₁₀₇Ti>Cu₁₀₇Si>Cu₁₀₇P>Cu₁₀₇Sn>Cu₁₀₇A l.Among them,the electrical conductivity of Cu₁₀₇Zn and Cu₁₀₇Ni alloys is relatively high,and their values are 2.97 and 2.77*10⁷S/m,respectively,while the electrical conductivity of Cu₁₀₇Al and Cu₁₀₇Sn alloys is lower,and their values are 1.93 and 1.91*10⁷S/m,respectively.