| The electronics industry has been rapidly advancing in recent years. As the coretechnology in the electronic products, electronic packaging technology has attractedextensive attention. Sn-Cu solder is widely used in wave soldering which is a vitalstep of the electronic packaging. Because Sn-Cu hypoeutectic solder has moreadvantages than eutectic solder, Nanoparticles of Ni and Co with different proportionswere added into Sn0.65Cu hypoeutectic solder matrix in this present paper, and theeffects of nanoparticles upon solder tissue, mechanical properties, melting point,wettability and the interfacial IMC were studied. The results show as follows:Firstly, after being added with nanoparticles of Ni and Co, solder tissue does notmake a huge difference except that the primary β-Sn phase has refined to a certaindegree in the tissue,. along with the changes in the proportion of the added particles.Cu in the solder will be replaced by Ni and Co to form a small partial hexagons (Cu,Ni)6Sn5phase and (Cu, Co)6Sn5phase, and these phases disperse in solder. Addingan excessive amount of Ni particles will cause agglomeration and enlarge the soldertissue.Secondly, mechanical experiments’ results indicated that the mechanicalproperties of Sn-0.65Cu+0.3Ni and Sn-0.65Cu+0.3Co are the best. The tensilestrength of Sn-0.65Cu+0.3Ni solder is40.13MPa which increases15.5%and thedocking strength is36.88Mpa which increases17.7%compared with that of thematrix respectively; Besides, the tensile strength of Sn-0.65Cu+0.3Co is42.32MPawhich increases21.7%and the docking strength is38.91Mpa which increases24%compared with that of the matrix respectively, and the elongation of solder willdecrease along with increasing the content of Ni and Co.Thirdly, After being added with Ni particles, the onset of solder’s meltingtemperature decreases from227.1℃to225.4℃, the minimum value ofSn-0.65Cu+0.1Ni solder, and then it will be gradually increasing to226.7℃ofSn-0.65Cu+0.7Ni solder; After being added with Co particles, the onset of solder’smelting temperature decreases from227.1℃, and thatof the Sn-0.65Cu+0.5Co solderwill be as low as225.7℃, during which the change is quite subtle. At this moment,the melting range increases from5.8℃to6.3℃.Fourthly, at260℃, it is Sn-0.65Cu+0.1Ni and Sn-0.65Cu+0.3Co whose wettability plays the best performance. The maximum wetting force ofSn-0.65Cu+0.1Ni can reach3.29mN, which increases5.8%compared to that of thematrix solder; and the wetting time is1.01s which has a slight growth compared tothat of the matrix solder. The spreading rate is79.6%which increases18.5%compared to the matrix solder. The maximum wetting force of Sn-0.65Cu+0.3Coanreach3.25mN, which increases4.2%compared to that of the matrix solder. Thewetting time is0.83s and the spreading rate is79.1%. Sn-0.65Cu+0.3Co increases17.7%compared to the matrix solder.Finanlly, after being added with nanoparticles of Ni, Co, the scallop features ofCu6Sn5in the interfacial IMC layer disappears, transiting to lamellar morphology,and the uneven tissue gradually becomes flat. The thickness of the interfacial IMCthickens along with the increase of nanoparticles. Moreover, the growth rate ofinterfacial IMC far exceeds that of the matrix solder. |
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