Effect Of Nickel Nanoparticles On The Performance Of Low Silver Solder

With the development of microelectronics and surface mounted technology, newlead-free solders have been an important research topic. But the most widely usedSn-Ag-Cu solder alloy is high silver solder, which costs too much. In this thesis,low-cost low-Sn-0.3Ag-0.7Cu solder alloys is studied by adding Ni nanoparticles toimprove the performance deficiencies of low silver solder. It is expected to findcomposition ratio which make solder possessing good properties for mechanicalshocking resistance and creep fatigue performance. Using two ways of addingtechnology, the thesis analyzes the effects of Ni on microstructure, solder alloy meltingpoint, wettability, hardness and shear performance.Studies show that a small amount of Ni added to solder can refine the organization.Small intermetallic compounds can play a role in strengthening the organization. Niatom can replace the Cu in Cu6Sn5and form (Cu, Ni)6Sn5, which changes themorphology of the intermetallic compound. The added Ni mainly distributed inintermetallic compound. It can also change the distribution of Ag3Sn in solder. Whenexcess Ni is added, IMC will grow up and the strengthening effect will diminish or evendisappear. Between the solder ball and the Cu pad, Ni can change the morphology ofIMC from scallop-shaped to jagged or island.From a view of macro performance, trace amounts of Ni has little effect on thesolder melting point and corrosion resistance. With content of Ni increase solderhardness increase and then decrease. The change of solder microstructure is directlyrelated to Ni addition. A small amount of Ni can serve to strengthen the solder. Thechange in resistivity and hardness is consistent. Fine intermetallic compound hinderedthe current. Ni can increase the shear strength. And a small amount of Ni changes brittlefracture to mixed fracture.Mechanical adding process is a simple method at room temperature, using oleicacid as a dispersant to avoid agglomeration of nano-Ni. But there is some Ni overflowed.This is because of the surface tension of Sn in the reflow process and the liquid solderwill not have time to react with Ni. To determine the amount of Ni in overflow, thesolder surface scanning through the EDS analysis residue Ni. Residual Ni can affect thesolder microstructure and performance. Microstructure and performance have the sametrend with the solder alloys.