Study On The Effect Mechanism Of Mo And Ag On Interfacial Reaction Of In-Sn Encapsulated Alloy

With the rapid development of portable electronic equipment and the use of flexible polymer substrates,In-48Sn solder has attracted wide attention from researchers.However,the traditional In-48Sn solder is difficult to meet the needs of integrated circuits due to its weak creep resistance and low shear strength of the solder joint.In this paper,In-48Sn-Mo solders and In-48Sn-xAg solders were prepared by melting combined with mechanical rolling method.The effects of Mo content,Mo particle gradation and Ag content on the melting characteristics,wettability,microhardness,thermal conductivity,density,creep behavior under nanoindentation,electrochemical corrosion behavior,IMC morphological evolution at the interface,the growth behavior of IMC and interfacial reaction mechanism of the solders were researched.The Mo precipitation process at the interfacial layer was reproduced by depleting the solder matrix,and it was found that Mo has the effect of improving the stability of the interfacial layer.The alloy properties were improved by changing the micro-nano Mo gradation.The comparative analysis of Mo and Ag on In-48Sn strengthened solders showed that both can improve the mechanical properties of solders and inhibit the growth of IMC layer,but Ag will reduce the electrical conductivity and thermal conductivity of the encapsulated alloy and change the fracture pattern of the solder joint.Mo elements in the In-48Sn solder were present as Mo,and Ag elements in the In-48Sn solder were present as Ag_3（）In,Snphase.Melting characteristics,thermal conductivity and density of In-48Sn-Mo alloys were less affected by variations in Mo content and micro-nano Mo gradation.The melting point and thermal conductivity of In-48Sn-Ag series alloys were negatively correlated with Ag content,and the density increased with increasing Ag content.The average grain size,microhardness,creep behavior under nanoindentation,electrochemical corrosion resistance,and shear strength of In-48Sn-Mo alloys first increase and then decrease as the Mo content increases and the micro-nano Mo gradation changes.The wettability of solders was negatively correlated with Ag content and positively correlated with temperature.Mo and Ag elements can inhibit the growth of IMC layer in Solder/Cu joints.In-48Sn-0.4Mo/Cu joints and In-48Sn-0.4Mo（nm:μm=1:2）/Cu joints shear strength was 22 and24 MPa,respectively,and the fracture mode was ductile fracture.The shear strength of the Cu/In-48Sn-3Ag/Cu joint was 24 MPa.The fracture mode of Cu/In-48Sn-xAg/Cu joints changed from ductile fracture to mixed tough-brittle fracture as the Ag content increased.With the increased of welding time,the fracture mode of the joint transformed from ductile fracture to brittle fracture.