| The development of the times brings technological progress,more and more electronic products come into people's lives,the microelectronics industry has become the core of the production of electronic products,the most important part of the microelectronics industry is electronic packaging technology.Therefore,in order to meet the needs of the industry,a variety of electronic packaging technologies have been developed.The most representative of which is BGA packaging technology.The primary research of BGA packaging is the choice of solder.The solder needs to be pollution-free and harmless to the human body.So the traditional Sn Pb solder is limited.At present,Sn Ag Cu series solder is a common substitute for Sn Pb solder,which is close to traditional Sn Pb solder due to its excellent performance.The low-silver Sn Ag Cu series solder has been widely studied because of its high cost performance.In this paper,the mechanical behavior of the solder joints of low silver SAC0307-x La(x=0? 0.03?0.05? 0.07?0.10)with rare earth elements was studied by applying shear load(cyclic loading,once loading)in the shear direction with nano-indentation method.After the cyclic shear test and once shear test through the nano-indentation equipment,it was found that in the cyclic shear test,the indentation depth of SAC0307-x La/Cu solder joints is only related to the maximum shear load and increases with the increase of shear load;The change trend of the Hit value of the solder joint has nothing to do with the loading parameters,and they are gradually reduced;For the indentation morphology,the increase of the maximum load and the holding time will make the indentation depth deeper,the increase of the loading time and loading rate will also produce wrinkles=The creep of the indentation is mainly related to the loading time,which increases with the increasing of the loading time,but the increase gradually tends to be gentle.In a shear test,the indentation depth of SAC0307-x La/Cu solder joints is mainly related to the holding time and maximumshear load,which increases with the increase of the holding time and shear load;The change trend of indentation hardness value is the same,which is a gradual decline,but the creep degree of indentation will gradually increase,and wrinkles will gradually occur around the indentation.The comparison between the two groups of experiments can be concluded that the addition of La element significantly improves the mechanical properties of the solder joint,increases the hardness and plasticity,and decreases the creep index.The optimal effect was 0.05%.When the content of La exceeded 0.05%,the hardness and plasticity of the solder joint decrease inversely,which was related to the fact that La element was concentrated at the grain boundary and weakened the grain boundary.The shear fracture analysis test shows that the shear strength of solder joints increases with the increase of loading speed,but the increase degree reduced gradually.In the aspect of plasticity,the fracture displacement decreases with the increase of loading speed,but the decrease degree decreases gradually.Scanning the fracture surface of five kinds of solder joints under the maximum and minimum loading speeds,it is found that: SAC0307 solder joints show brittle fracture under the three loading speeds,there are more flat areas on the fracture surface,and the number of dimples is very small;the other four solder joints show mixed fracture under the maximum and minimum loading speeds;Among the five kinds of solder,SAC0307-0.05 La solder has the best plastic solder spot,the dimples on the fracture surface are evenly distributed,showing a parabolic shape,the dimples are deep and the elongation is long. |
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