Investigation On Preparation And Thermal-Mechanical-Electrical Properties Of Sintered Copper Matrix Die Attach Materials For Wide Bandgap Semiconductor Packaging

With the development of high-density and high-power semiconductor devices and the increasing application of the wide bandgap semiconductor,it is critical to develop die attach materials with high thermal conductivity and reliability,while meeting the power electronic device requirements of low-temperature packaging and high-temperature service.Sintered nano copper die attach materials with high thermal conductivity,high electron migration resistance and low cost have attracted much attention.However,the density of sintered nano copper is low because copper nanoparticles are easy to be oxidized and resulting in the properties of sintered copper are much lower than expected.In this thesis,tin with low melting point was introduced to fabricate die attach materials with copper matrix.The properties of sintered tin-copper die attach can be improved with tin filled in the voids of among copper nanoparticles.The sintering neck is easy to form between copper particles with contact area improved by filled tin.As a result,the density and properties of sintered copper are enhanced.This thesis studies two ways of introducing tin:(1)Tin nanoparticles and copper nanoparticles are simply mixed.Tin nanoparticles and copper nanoparticles are easy to be oxidized and need deoxidization treatment.The deoxidized tin nanoparticles and nano copper are mixed with solutions and followed by sintering.(2)Tin plated copper particles are fabricated and mixed with copper nanoparticles.Electroless tin plating has the advantages with simple operation and uniform coating.A thin tin layer was successfully coated on copper particles.The effects of the addition amount of tin and tin coated copper particles were experimentally investigated on properties of sintered copper based die attach.The experimental results show that shear force of 102 MPa,thermal conductivity of 177 W/(m·K)and electrical resistivity of 0.95×10^-7?·m are achieved with 1%tin filled in copper die attach.Shear force of 71MPa,thermal conductivity of 188 W/(m·K)and electrical resistivity of 0.92×10^-7?·m are achieved with 5%tin plated copper particles filled in copper die attach.