Material And Reliability Study On 3D Packaging Interconnection Based On CNTs/Cu Particles Enhancement

With the rapid development of electronic information industry,the development of the electronic packaging technology and material has been concerned widely.The traditional Sn Pb solder will step down from the stage of history gradually and only be used in special industries due to the toxicity of Pb.In recent years,the research on Sn based lead-free solder has attracted much attention.Typical representatives include Sn Ag Cu,Sn Cu,Sn Zn and Sn Bi.There are few reports about In based,Au based,Ni based or other lead-free solders.In based low temperature solders have become one of the main special solders for microelectronic assembly because of their low melting point,good fatigue resistance and high reliability.In this paper,In based composite solders containing nano Cu particles and CNTs were prepared.The influence of nano materials on the microstructure and properties of solders were studied.The similarities and differences of the influence of nano Cu particles on In and Sn solder were analyzed.Then the effect of nano Cu particles on the reliability of solder joints was studied by aging.In addition,the effect of thermal shock on the reliability of In solder joint and Sn Pb solder joint in FCBGA device was studied by finite element method.The results show that:The microstructure of In-xCu/Cu solder joint is mainly composed of In rich phase and Cu-In compounds.With the addition of nano Cu particles and 0.05%CNTs,the size of In rich phase decreased,and the proportion of Cu in structure in the matrix increased.This refining effect was obvious when the amount of Cu particles reached 1.6%.On the other hand,the addition of nano Cu particles had little effect on the interface morphology of In-x Cu/Cu solder joints,but it can inhibit the growth of IMC.In addition,it was found that the voids and gaps in In-x Cu/Cu solder joints appeared between the internal solder and the interface IMC layer,which was different from Sn/Cu bonding.The results spreading experiment showed that the wettability of Sn solder can be improved by adding 0.7%nano Cu particles.For In solder,the wettability was reduced by nano Cu particles.When the content of nano Cu particles reached 2.0%,the spreading area reduced from the initial value of 105.7mm~2to 87.4mm~2,with a decrease rate of 17.3%.When the soldering temperature increased from 175? to 185?,the spreading area of In-1.6Cu and In-1.6Cu-0.05CNTs increased from 89.9mm~2and93.4mm~2to 94.3mm~2and 98.5mm~2,respectively.In addition,0.05%CNTs increased the spreading area of In-1.6Cu solder to a certain extent,but it was still smaller than that of In solder.It was found by DSC tests that the effect of nano Cu particles on the melting characteristics of In and Sn solder was in accordance with the binary phase diagrams.However,the addition of nano Cu particles had little effect on the melting point of the alloy,but the melting range of the alloy decreased from 2.19? to 1.24?.If only consider the melting characteristics,the best addition amount of nano Cu particles is1.6%.The mechanical experiment of the solder joint showed that the addition of nano Cu particles can improve the mechanical properties of the solder joint,and when the amount of Cu particles is 1.6%,the tensile force and shear force of the solder joint reached the maximum value at the same time,8.46N and 49.7N,which is higher than the initial value by 17.0%and 18.9%,respectively.In addition,the shear force of In-1.6Cu/Cu solder joint increased by 9.9%with the addition of 0.05%CNTs due to the refinement of matrix structure and the effect of grain boundary strengthening.The interface IMC of In-(1.6)Cu/Cu solder joint grew rapidly after aging at 175?.The growth rate of interface IMC slowed down slightly with the extension of aging time.The addition of 1.6%nano Cu particles can inhibit the growth rate of IMC in aging state to a certain extent by reducing the diffusion coefficient of elements.With the increase of aging time,the shear force of Cu/In/Cu and Cu/In-1.6Cu/Cu solder joints decreased.After aging for 5min,10min and 30min,the shear force of Cu/In/Cu solder joints decreased by 5.3%,8.9%and 19.9%respectively,while that of Cu/In-1.6Cu/Cu solder joints decreased by 4.9%,8.7%and 15.1%respectively.Under the condition of thermal shock,the creep stress and creep deformation of In solder joints were significantly less than that of Sn37Pb solder joints.In addition,the fatigue life of In solder joints was1054 and that of Sn-37Pb solder joints was 738,which showed that In solder has the higher reliability in FCBGA devices relatively.In addition,the results of thermal cycling experiments show that the tensile force of In-1.6Cu-0.05CNTs and Sn-0.7Cu solder decreased linearly with the increase of thermal cycling times,and the fatigue life of In-1.6Cu-0.05CNTs solder was 1255,and that of Sn-0.7Cu solder was 1052.