INFLUENCE OF NICKEL LAYER THICKNESS ON PHASE GROWTH IN CU-NI-SN SYSTEM DURING ISOTHERMAL ANNEALING
Main Article Content
Abstract
For modern gadgets and other microelectronic devices, the main requirement is their reliability. One of the reasons of the failure is the overheating of the equipment and the further degradation of the solder contacts. This process is induced by the formation of pores in the intermediate ε-Cu3Sn phase, which is formed during heating of the copper-tin contact. It should be noted that not only overheating leads to the degradation of the solder contact, but also the electric current through the contact.
There were many studies to determine the factors that supress the growth of pores in the ε-Cu3Sn phase, as well as the growth of this phase. One of such factor is the addition of zinc or nickel to the solder on the tin base. The addition of a microscopic layer of nickel to the boundary between copper and tin was also investigated.
The kinetics of phase growth in the Cu-Ni-Sn system under isothermal annealing at 340°C is investigated. The study of this three-component system is relevant, since pores can form at the Cu-Sn interface, which affect the contact properties and can serve as places of occurrence of defects (pores).
It should be noted that the thickness of the phases correlates with the number of pores formed and their size. Therefore, the study of the diffusion reaction in the Cu-Sn system with the addition of another component is one of the ways to inhibit the growth of the Cu6Sn5 + Cu3Sn phases. In the paper, the thickness of the Cu3Sn + Cu6Sn5 phase layer was inestigated at different annealing times at a temperature of 340°C. The total annealing time was 10 hours. It is shown that at a certain thickness of the deposited nickel, the growth of the ε-Cu3Sn phase almost completely stops. On the basis of the obtained experimental data, the dependences of the phase thickness on the annealing time for different initial thicknesses of the nickel layer are presented. It is shown that the thickness of the nickel layer significantly affects the growth kinetics of the Cu3Sn + Cu6Sn5 phase layer.
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References
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